a guide to weeds in british columbia · growth form: annual forb. flower: several small (less than...

A Guide to Weeds in British Columbia

ii

Developed in cooperation with the British Columbia Ministryof Agriculture, Food and Fisheries, the Guide to Weeds inBritish Columbia has been produced by the Open LearningAgency. The Open Learning Agency is grateful to the Divisionof Plant Industry, in the Colorado Department of Agriculture,for permission to use and substantially adapt Appendix 4:Profiles of Colorado State-Listed Weeds from Creating anIntegrated Weed Management Plan: A Handbook for Ownersand Managers of Lands with Natural Values in The Caring forthe Land Series, Volume IV (March 2000) by Alan T.Carpenter and Thomas A. Murray of Land StewardshipConsulting, Inc., Boulder, Colorado, and Karin Decker.

Dr. Brian Wikeem, co-author of the Field Guide to theBiological Control of Weeds in British Columbia: LandManagement Handbook Number 27 (1994), and SandraWikeem, adapted appendix 4 of the Colorado handbook forBritish Columbia. Roy Cranston and David Ralph, on behalfof the British Columbia Ministry of Agriculture, Food andFisheries, reviewed all materials associated with this project.Their involvement has been critical to its completion.Illustrations in the Guide to Weeds in British Columbia arereprinted by permission of the University of WashingtonPress from Vascular Plants of the Pacific Northwest by C.Leo Hitchcock, Arthur Cronquist, Marion Ownby, and J. W.Thompson (5 Vols., 1955-69), illustrated by Jeanne R.Jannish and John H. Rumely, and from Volumes 1 to 7 of TheIllustrated Flora of British Columbia (1998 – 2000) by G.W.Douglas, et al. Gail F. Harcombe, graphics specialist from theBritish Columbia Ministry of Water, Land and Air Protection,provided electronic versions of the graphics in Douglas et al.The illustrations from this volume are by Elizabeth Stephens,Jane Lee Ling, and Sherry Mitchell. Paul Pryce of the OpenLearning Agency contributed original illustrations ofcommon crupina, jointed goatgrass, purple nutsedge, yellowstarthistle, tartary buckwheat, and quack grass.

The Integrated Weed Management Project was overseen bythe following advisory committee members: Roy Cranston,David Ralph, Elaine Russell, Marney James, and Edi Torrans.

The overall steering committee for the three agriculture-related projects comprised John Schildroth (chair), Ron Sera,Marney James, Linda Chase Wilde, Grant Thompson, LarryBomford, Tim Winkelmans, and Michelle Nicholson.

The Open Learning Agency staff responsible for this projectincluded: Dini Steyn, project manager; Michelle Nicholson,budget; Gale Parchoma and John Stape, editors; KeithLearmonth, copy editor; Paul Pryce, art director; Paul Pryceand Martha Shiu, page design and layout; Jason Pryce,project assistant, and Rita Nienaber, copyright.

WeedsBC, 1st Edition, ISBN 1-55139-019-1 Set

Guide to Weeds in British Columbia, 1st Edition, ISBN 1-55139-021-3

Seven Steps to Managing Your Weeds,1st Edition, ISBN 1-55130-023-x

This project also includes:• Weed Watch, a video for weed awareness workshops

• Weed awareness public service announcements

• WeedBC, a website at http://weedsbc.ca

Copyright © 2002 Province of British Columbia

All rights reserved. No part of this work may be reproduced inany form by any means without permission in writing from theBritish Columbia Ministry of Agriculture, Food and Fisheries.

Warranty Disclaimer

This publication and all of the information it contains isprovided “as is” without warranty of any kind, whetherexpressed or implied. All implied warranties, including,without limitation, implied warranties of merchantability,fitness for a particular purpose, and non-infringement, arehereby expressly disclaimed.

Limitation of Liabilities

Under no circumstances will the Government of BritishColumbia be liable to any person or business entity for anydirect, indirect, special, incidental, consequential, or otherdamages based on any use of the information in thispublication, including, without limitation, any lost profits,business interruption, or loss of programs or information,even if the Government of British Columbia has beenspecifically advised of the possibility of such damages.

Printed and Distributed by the Open Learning Agency

For Order Information Contact

Open Learning Agency Marketing DepartmentTelephone: (604) 431-3210Toll Free: 1-800-663-1653Fax: (604) 431-3381Email: [email protected]: 4355 Mathissi Place

Burnaby, British ColumbiaCanada V5G 4S8

Visit Our Website at www.weedsbc.ca

Cover design and artwork by Paul Pryce

ACKNOWLEDGEMENTS


iii

Introduction

Alphabetical Weed List (Common name followed by the Latin name)

Annual sow thistle Sonchus oleraceus 2

Barnyard grass Echinochloa crusgalli 4

Black knapweed Centaurea nigra 6

Black nightshadeSolanum americanum var: nodiflorum 8

Blue mustard Chorispora tenella 10

Blueweed Echium vulgare 12

Bog rush Juncus effusus 14

Bull thistle Cirsium vulgare 16

Canada thistle Cirsium arvense var: horridum 20

Cheatgrass Bromus tectorum 24

Chicory Cichorium intybus 28

Cleavers Galium aparine 30

Coast tarweed Madia sativa 32

Common bugloss Anchusa officinalis 34

Common burdock Arctium minus 36

Common chickweed Stellaria media 38

Common crupina Crupina vulgaris 40

Common groundsel Senecio vulgaris 42

Common tansy Tanacetum vulgare 44

Corn spurry Spergula arvensis 46

Creeping buttercup Ranunculus repens 48

Curled dock Rumex crispus 50

Dalmatian toadflaxLinaria genistifolia ssp. dalmatica 52

Diffuse knapweed Centaurea diffusa 56

Field bindweed Convolvulus arvensis 60

Field horsetail Equisetum arvense 64

Field scabious Knautia arvensis 66

Flixweed Descurainia sophia 68

Gorse Ulex europaeus 70

Green foxtail Setaria viridis 74

Hairy Nightshade Solanum physalisfolium 76

Hemp-nettle Galeopsis tetrahit 78

Hoary alyssum Berteroa incana 80

Hoary cress Cardaria draba 82

Hound's-tongue Cynoglossum officinale 86

Jointed goatgrass Aegilops cylindrica 90

Kochia Kochia scoparia 92

Lady's-thumb Polygonum persicaria 94

Lamb's-quarters Chenopodium album 96

Leafy spurge Euphorbia esula 98

Marsh plume thistle Cirsium palustre 102

Meadow knapweed Centaurea debauxii 104

Night-flowering catchfly Silene noctiflora 106

Nodding thistle Carduus nutans 108

Orange hawkweed Hieracium aurantiacum 112

Oxeye daisy Leucanthemum vulgare 114

Parasitic dodder Cuscuta spp. 116

Perennial pepperweed Lepidium latifolium 118

Perennial sow thistle Sonchus arvensis 120

Plumeless thistle Carduus acanthoides 124

Poison hemlock Conium maculatum 126

Puncturevine Tribulus terrestris 128

Purple loosestrife Lythrum salicaria 130

Purple nutsedge Cyperus rotundus 134

Quackgrass Elytrigia repens 136

Redroot pigweed Amaranthus retroflexus 138

Rush skeletonweed Chondrilla juncea 140

Russian knapweed Acroptilon repens 144

Russian thistle Salsola kali 148

Scentless chamomile Matricaria perforata 150

Scotch thistle Onopordum acanthium 152

Sheep sorrel Rumex acetosella 154

Shepherd's-purse Capsella bursa-pastoris 156

CONTENTS

Spotted knapweed Centaurea biebersteinii 158

Squarrose knapweedCentaurea virgata var: squarrosa 162

Stork's-bill Erodium cicutarium 164

St. John's-wort Hypericum perforatum 166

Sulphur cinquefoil Potentilla recta 168

Tansy ragwort Senecio jacobaea 170

Tartary buckwheat Fagopyrum tataricum 172

Velvetleaf Abutilon theophrasti 174

Water hemlock Cicuta douglasii 176

White cockle Silene latifolia ssp. alba 178

Wild chervil Anthriscus sylvestris 180

Wild mustard Brassica kaber 182

Wild oats Avena fatua 184

Wild proso millet Panicum miliaceum 186

Yellow nutsedge Cyperus esculentus 188

Yellow starthistle Centaurea solstitialis 190

Yellow toadflax Linaria vulgaris 192


iv

The issue of weed management in the province ofBritish Columbia is of ongoing concern tolandowners, land managers, and of course, to theBC Ministry of Agriculture, Food and Fisheries.Several valuable publications, including the FieldGuide to Noxious Weeds and Other SelectedWeeds of British Columbia (1996), already assistin the identification of noxious weeds. However,simply knowing which weeds infest an areacannot solve the problem. A comprehensiveresource geared toward providing an integratedapproach to weed population management haslong been needed. In the year 2000, the Ministryidentified six projects for development throughBC’s Open learning Agency (OLA). TheIntegrated Weed Management Project was one.

The Ministry is grateful for the cooperation andassistance provided by the State of Colorado inmaking this project a success. The State ofColorado published a weed managementhandbook, Creating an Integrated WeedManagement Plan: A Handbook for Owners andManagers of Land with Natural Value in 2000. In2001, the Ministry and OLA acquired permissionto adapt this resource to the needs of the citizensof British Columbia.

At the outset of the adaptation process twoadditional goals were identified. First, team andcommunity members voiced a concern about lackof public awareness of the negative impact ofnoxious weeds on agricultural enterprises and thenatural environment. A decision was made toproduce a series of public service announcements

(PSA’s) for broadcast on the Knowledge Networkand privately owned television stations. A set offive PSA’s was produced, and it is hoped that theywill inform recreationalists, as well ashomeowners and landowners, of the implicationsof an unchecked increase in noxious weedpopulations. Secondly, a need for awareness andmanagement training sessions was identified. ATrain-the-Trainers workshop in Kamloopsprovided a group of agricultural specialists withexperience in using the Seven Steps to ManagingYour Weeds: A Manual for Integrated WeedManagement in British Columbia, a companionresource for the Guide to Weeds in BritishColumbia. A capstone video, Weed Watch, hostedby Sue Ellen Fast, was added to the set of trainingmaterials.

As the project progressed, the decision was madeto make information available on the World WideWeb. Weeds BC was created to provide free andopen access to information for the public. Pleasecheck out the Weeds BC site athttp://www.weedsbc.ca. You will find informationon weed identification, impacts, and managementstrategies, as well as noxious weed legislation.The fully searchable site is a valuable andaccessible source of information on the preventionof destructive weed populations in BritishColumbia.

Gale Parchoma (Editor)Dini Steyn (Project Manager)


1

INTRODUCTION

Habitat and Ecology __________________________________

Growth form: Annual forb.

Flower: Several small (less than 2.5 cmacross), yellow dandelion-like flower heads

on sometimes glandular stalks are grouped inopen, flat- or round-topped clusters.

Seeds/Fruit: Seeds are 2.5–3.5 mm long,reddish brown and ribbed with aparachute-like pappus.

Leaves: Leaves are deeply lobedand basal leaves end with alarge, pointed segment. Leafmargins have small, weakteeth (Frankton and Mulligan1970). Basal leaves are stalked,but upper leaves are stalklessand clasp the stem.

Stems: Mature plants are 0.1–1.0m tall. The single stems are erect and

branched only near the top. The hollow stems exude amilky juice when cut (Douglas et al. 1998).

Roots: A short taproot.

Seedling: No information available.

Similar Species

Exotics: Perennial sow thistle (Sonchus arvensis) differsfrom annual sow thistle in its extensive creeping rootsand larger flower heads. Prickly annual sow thistle(Sonchus asper) has very prickly leaf margins, and itsleaves are rarely sharply lobed. Wall lettuce (Lactucamuralis) has a fibrous root system, numerous flowerheads, and an ivy-like segment on the end of the leaves.

Natives: Several native lettuces (Lactuca sp.)resemble annual sow thistle, but they tendto have more numerous flower heads andlack the distinctive large, pointed lobe onthe end of the basal leaves.

Agricultural: A common weed of cultivated crops,grain fields, and orchards. It acts as an alternate host toaphids, several viral diseases, and nematodes(Hutchinson et al. 1984).

Ecological: Invades both native plant communities anddisturbed sites. Rapid germination and establishmentcombined with wind dispersal of seeds over greatdistances allow annual sow thistle to colonize newareas rapidly. They are adapted to a wide range of

environmental conditions but are most competitive intemperate climates with abundant moisture (Zollingerand Parker 1999). They tolerate saline soils but arebetter adapted to slightly acid to alkaline soils(Hutchinson et al. 1984). This weed tolerates saturatedsoils and can be a problem in marshes, ponds, andother riparian areas.

Human: Sow thistles contain chemical compoundsused for industrial and pharmaceutical purposes.

ANNUAL SOW THISTLE

Sonchus oleraceus L.Family: Asteraceae (Sunflower).

Other Scientific Names: None.

Other Common Names: Common sow thistle, spiny-leaved sowthistle, spiny annual sow thistle, spiny milk thistle, prickly sowthistle, sharp-fringed sow thistle.

Legal Status: Provincial Noxious.


2

Impacts ____________________________________________

D I S T R I B U T I O N

General requirements: This weed grows in a widerange of environments but does best on fertile, moistsoils in full sunlight. In BC, annual sow thistle growson cultivated fields, gardens, roadsides, riparian areas,and disturbed sites such as gravel pits and logged areas.

Distribution: Most frequent in the province’s southerncoastal regions but present in all agricultural reportingregions. It occurs in all Canadian provinces andthroughout the northern US.

Historical: Introduced from Europe.

Life cycle: Annual sow thistle usually overwinters asseeds, but plants may overwinter as rosettes. Seedsgerminate from spring through autumn. Plants formrosettes, then bolt, flower, set seed, and complete theirlife cycle rapidly. Flowers are produced from June toearly October. Sometimes a second generation grows inone growing season.

Mode of reproduction: By seed.

Seed production: Each plant produces about 6,100seeds. Seed production is greater when there isadequate moisture.

Seed bank: Seeds remain viable for several years incultivated soil.

Dispersal: The tall stalks, lightweight seeds, andparachute-like pappus promote dispersal by wind(Hutchinson et al. 1984). Seeds can also disperse bywater, be ingested by birds and animals, and attach tofur or feathers.

Hybridization: Leaves of some plants appear to beintermediate between annual sow thistle and spiny-annual sow thistle (Sonchus asper), but true hybrids arerare (Hutchinson et al. 1984).

Douglas, G. W., G. B. Straley, D. Meidinger, and J.Pojar, eds. 1998. Illustrated Flora of British Columbia.Vol. 1: Gymnosperms and Dicotyledons (Aceraceaethrough Asteraceae). Province of British Columbia.

Frankton, C., and G. A. Mulligan. 1970. Weeds ofCanada. Publication 948. Ottawa: Canada Departmentof Agriculture.

Hutchinson, I. J., J. Colosi, and R. A. Lewin. 1984. Thebiology of Canadian weeds. 63. Sonchus asper L. Hilland S. oleraceus L. Canadian Journal of Plant Science64: 731–744.

Zolinger, R. K., and R. Parker. 1999. Sowthistles. In R.L. Sheley and J. K. Petroff, eds. Biology andManagement of Noxious Rangeland Weeds. Corvallis:Oregon State University Press.

Biocontrol: Cystiphora sonchi forms galls onvegetative parts of the plant but has not been approvedfor release in BC. Sow thistle is palatable for cattle orsheep, and intensive grazing can suppress infestationson some sites by preventing seed-set.

Mechanical: Seed production can be prevented bymowing before seed-set, but mowing must be lowerthan 20 cm to prevent regrowth. In mild climates wherethe plants overwinter as rosettes, repeated tillage fromlate August to freeze-up gives excellent management.Tillage during March through May manages springannuals as they emerge (Hutchinson et al. 1984).Cultivation every three months can stimulategermination and eventually deplete the seed bank.

Fire: Fire is unlikely to manage annual sow thistle.Improved fertility following fire, such as on loggingslash piles, may make an ideal seedbed for this weed.

Herbicides: Annual sow thistles are susceptible tomany pre-emergence herbicides such as simazine andatrazine on cropland and dichlobenil on non-cropland.Foliar applications of MCPA, MCPB, 2,4-D, and 2,4-DB obtain good management post-emergence(Hutchinson et al. 1984). Selective herbicides appliedbefore blooming can prevent seed production. Consultthe most recent edition of BC Ministry of Agriculture,

Food and Fisheries Crop Production Guides forspecific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Preventive measures includeremoval of seedlings by cultural or chemical meansbefore they establish and set seed, managing weeds onfield borders, and planting weed-free crop seed.

Small infestations can be hand-pulled.


3

Integrated Management Summary

On cultivated areas an integrated approach ofintensive cultivation, competitive crops,selective herbicides, or a combination of all 3may be practical. On rangeland and undisturbedareas, seedlings on new infestations can behand-pulled or herbicides applied. Establishedpopulations may be managed with intensivegrazing or herbicides. Chemical control maynot be possible on the riparian areas where thisweed commonly occurs.

Management ________________________________________

References __________________________________________


Growth form: Annual grass.

Flower: Seed headsare often purplish

and consist of crowded spikeletswith large seeds. Awns (bristlyhairs) may be absent orup to 2.5 cm long(Whitson et al. 1996).

Seeds/Fruit: The seedsresemble millet. They areabout 3 mm long, shiny, andcan be white, yellowish,greyish, or brown (Franktonand Mulligan 1970).

Leaves: The leaves arelong, flat, 1.0–1.5 mm wide,slightly roughened tosmooth, and lack ligules(membranes where the bladejoins the stem).

Stems: Stems are 0.3–1.5 m tall. They are usually erectbut may spread over the ground. Stem bases are oftenreddish to dark purple (Whitson et al. 1996).

Roots: Fibrous.

Seedling: Leaves may be slightly red atthe base and have pointed tips. The stemis somewhat flattened until the 3-leafstage (Royer and Dickinson 1999).

Similar Species

Exotics: Can be distinguished from all othergrasses in the province by the lack of ligules.

Natives: Some authorities recognize another barnyardgrass (Echinochloa pungens). Many manuals consider thisthe same species since the 2 forms are so similar and theplants often hybridize. The Echinochloa pungens formwas originally confined to open ground, such as erodingriverbanks, but now has spread to roadsides, lawns, andcultivated fields (Frankton and Mulligan 1970).

Agricultural: Considered one of the world’s worstweeds, it is widespread in irrigated fields, gardens,barnyards, and other cultivated soils. It reduces cropyields and causes forage crops to fail to establish byremoving up to 80% of the available soil nitrogen(Royer and Dickinson 1999). The high levels ofnitrates it accumulates can poison livestock. It acts asan alternate host for several mosaic virus diseases.Heavy infestations can interfere with mechanicalharvesting.

Ecological: Barnyard grass commonly occurs alongroadsides, ditches, railway rights-of-way, and indisturbed areas such as gravel pits and dumps. It alsoinvades riparian communities along riverbanks andshores of lakes and ponds.

Human: Used occasionally as a forage crop, but itgrows in sparse stands and requires considerablemoisture to be productive. The seeds are grown forhuman consumption in tropical Africa and Asia(Hitchcock 1971).

BARNYARD GRASS

Echinochloa crusgalli (L.) Beauv.Family: Poaceae (Grass).


Other Common Names: Large barnyard grass, cockspur grass,summer grass.

Legal Status: Not categorized.


4

Impacts ____________________________________________


General requirements: Requires a frost-free period of160–200 days, warm summer days, and abundant soil

moisture. It tolerates a wide variety of soil types but isbest adapted to areas with rich, moist soil and little

competition. In BC, it grows in moist open places,ditches, cultivated land, gardens, riverbanks, anddisturbed habitats.

Distribution: Occurs in southern areas of the provinceand is present in all agricultural reporting regions. Itranges across North America to the Maritimes andsouth to the states of Florida and California.

Historical: Introduced from Europe. Originallycultivated as a forage and sold as a “wonder grass.”

Life cycle: Barnyard grass overwinters as a seed. Itgerminates in late spring after the soil has warmed.Some seeds continue to germinate over the summer. Itcompletes its life cycle during the summer and diesafter seed production in September or October (Maunand Barrett 1986).

Mode of reproduction: Primarily by seed. Stems oftenroot from lower nodes that contact the soil, allowingthe plant to spread during the growing season, but newplants do not survive over the winter.

Seed production: Individual plants can produce up to40,000 seeds/year (Royer and Dickinson 1999). Seedproduction is highly variable and relates to growingconditions.

Seed bank: New seeds are dormant. Dormancy isoften broken by exposure to low winter temperatures,alternating spring temperatures, or spring flooding, butsome seeds remain dormant much longer. Deeplyburied seeds (over 8 cm) lose no viability for 3 years,and some seeds can remain viable up to 13 years(Maun and Barrett 1986).

Dispersal: Water, birds, insects, machinery, and animalfeet. Contaminated seed is probably the most commondispersal method.

Hybridization: Echinochloa crusgalli andEchinochloa pungens hybrids intergrade to be nearlyindistinguishable.


Hitchcock, A. S. 1971. Manual of the Grasses of theUnited States. Vol. 2. New York: Dover Publications.

Maun, M. A., and S. C. H. Barrett. 1986. The biologyof Canadian weeds. 77. Echinochloa crusgalli. (L.)Beauv. Canadian Journal of Plant Science 66:739–759.

Royer, F., and R. Dickinson. 1999. Weeds ofCanada and the Northern United States.Edmonton: University of Alberta Press.

Whitson, T. D. (ed.), L. C. Burrill, S. A.Dewey, D. W. Cudney, B. E. Nelson, R. D.Lee, R. Parker. 1996. Barnyard grass. Weeds of theWest. Western Society of Weed Science, in cooperationwith the Western United States Land Grant UniversitiesCooperative Extension Services, Newark, CA.

Biocontrol: None.

Mechanical: Repeated shallow spring tillage canreduce emergence. Mowing is not effective since itstimulates growth from lateral buds.

Fire: Not effective.

Herbicides: Barnyard grass exhibits resistance to anumber of herbicides, especially atrazine. In fact, theweed became a serious problem in some crops such ascorn only after chemical control removed competing,non-tolerant weeds. Pre-emergent herbicides are mosteffective, since the plants are most susceptible at theseedling stage and established plants are resistant tomsost chemicals. Consult the most recent edition of BCMinistry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Small infestations are easily

hand-pulled. Fertilizing with liquid manure can spreadviable seeds. Thoroughly compost manures fromlivestock that have eaten this plant. Do not movelivestock that have eaten barnyard grass ontouninfested areas.


5

Integrated Management SummaryEffective control relies on preventingestablishment and seed production. Usecultural control on small infestations before thepopulation can establish a seed bank and useappropriate herbicides on large infestations.Seed disturbed areas to perennial grasses andforbs to provide ground cover and competition.Manage grazing animals to maintain perennialplant communities.

Management ________________________________________

References __________________________________________


Growth form: Perennial forb.

Flower: Flower heads are solitary at theends of the branches. The flowers are rose to

purple, occasionally white, and all are tubular.Floral bracts have long,black fringes from a blackor dark brown triangularcentre that gives a blackappearance to the seedheads.

Seeds/Fruit: Theflattened seeds are lightbrown or light grey,3.0–3.5 mm long, with ashort, bristly tip (Douglas etal. 1998).

Leaves: Basal leaves areup to 15 cm long, areusually toothed orshallowly lobed, and havelong stalks. Upper leaves of

the stems are generally stalkless and narrow with entiremargins. Lower stem leaves are larger, on stalks, andgenerally lobed (Douglas et al. 1998).

Stems: Stems are erect, unwinged, freely branchednear the top, and 10–80 cm tall.

Roots: Black knapweed has both a vertical taproot andspreading lateral roots.

Seedling: Autumn emerging seedlingsoverwinter as a rosette of leaves.

Other: The whole plant is dull greenand covered with small, rough hairs.

Similar Species

Exotics: Black knapweed is distinguished from otherknapweeds by the floral bracts that have long, blackfringes from a black or dark brown triangular centre.The heads tend to be larger than those of diffuse orspotted knapweed.

Natives: Native members of the sunflower family canresemble knapweed in the seedling/rosette stage.

Agricultural: Black knapweed can infest disturbedrangeland and reduce forage production.

Ecological: Black knapweed does not establish readilyin healthy, natural habitats. It typically invades

disturbed areas and can form dense stands.

Human: No information available.

BLACK KNAPWEED

Centaurea nigra L.Family: Asteraceae (Sunflower).


Other Common Names: Lesser knapweed.



6

Impacts ____________________________________________


General requirements: Black knapweed has beenfound in BC at low- to mid-elevations along roadsidesand in fields. Outside the province it grows alongroadsides, riverbanks, and irrigation ditches, and inpastures, disturbed habitats, clear-cuts, and croplands.It can tolerate a wide range of environmentalconditions but appears best adapted to moist soils that

receive summer rainfall.

Distribution: Currently this species is rare in theprovince south of 51o N (Douglas et al. 1998). It is onlyknown to be present in the Kootenay and Ominecaagricultural reporting regions.

Historical: No information available.

Life cycle: Black knapweed generally flowers fromJuly through August. Seeds germinate from springthrough early autumn. Seedlings that emerge in theautumn often overwinter as a rosette of leaves andresume growth in the spring.

Mode of reproduction: By seed and occasionally fromroot shoots (Roche and Roche 1991).

Seed production: Black knapweed can produce over1,000 seeds/plant.

Seed bank: Seeds can remain viable in the soil forover 5 years.

Dispersal: People are the most significant agent forspread. Knapweed is often spread in hay and on vehicleundercarriages.

Hybridization: Black knapweed readily crosses withbrown knapweed (Centaurea jacea) to form the fertilehybrid, meadow knapweed (Centaurea debauxii).


Roche‚ B. F., Jr., and C. T. Roche. 1991. Identification,introduction, distribution, ecology, and economics ofCentaurea species. In L. F. James, J. O. Evans, M. H.Ralphs, and R. D. Child, eds. Noxious Range Weeds.Boulder, CO: Westview Press.

USDA, NRCS. 1999. The PLANTS Database. BatonRouge, LA: National Plant Data Center.http://plants.usda.gov/plants

Biocontrol: None.

Mechanical: Small infestations can be pulled andlarger infestations can be mowed, burned, or mulchedand then treated with herbicides as soon as newseedlings emerge.

Fire: No information available.

Herbicides: Picloram, dicamba, or a combination ofclopyralid and 2,4-D have all been used effectively tomanage black knapweed. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Minimize disturbance andestablish robust stands of grasses or forbs to out-compete black knapweed.


7

Management ________________________________________

References __________________________________________

Integrated Management SummaryLand managers must learn to identify knapweed.New infestations of this species should be a highmanagement priority. Timely management of afew plants is very cost-effective compared totreating larger acreage later. Since blackknapweed establishes in disturbed sites,persistent monitoring of commonly disturbedareas (e.g., roadsides, along trails, stream banks,and where hay is fed) is a good way to search fornew infestations. Manage knapweed infestationswith a combination of mechanical and chemicaltreatments. In addition, improving the health of anatural area and guarding against disturbance oroveruse are good preventive measures.


Growth form:Annual orshort-lived

perennial forb.

Flower: Flowers are whiteto pale blue, 5–10 mmwide, and borne in clusters.

Seeds/Fruit: The globe-shaped berries of blacknightshade are 8 mm wide.Green when immature butturn black upon maturity(Basset and Munro1985).

Leaves: Alternate, ovate, wavy-edged, and tapered.

Stems: Single-stemmed, erect, 15–60 cm tall. Smoothappearance.

Roots: Taproot.

Seedling: Ovate, tapering toa pointed tip.

Similar Species

Exotics: Black nightshade can bedistinguished from hairy nightshade(Solanum physalifolium) by its smooth stems andleaves, and the smaller covering(calyx) on top of the berry.

Natives: None known.

Agricultural: Commercial berry crop quality issignificantly reduced when black nightshade berriesmix with them. The plant also produces a stickysubstance that clogs agricultural equipment such ascombine screens and rotors (Basset and Munro 1985).

Berries can be poisonous to cattle, sheep, goats, pigs,ducks, and chickens (Basset and Munro 1985).

Ecological: No information available.

Human: Poisonous to humans.

BLACK NIGHTSHADE

Solanum americanum P. Mill. var.nodiflorum (N.J. Jacq.)Family: Solanaceae (Nightshade).

Other Scientific Names: Solanum nigrum.

Other Common Names: Garden nightshade, common nightshade.



8

Impacts ____________________________________________


General requirements: In BC, occupies dry tomoderately dry sites at low- to mid-elevations.Commonly found on disturbed soils such as roadsides,rights-of-way, cultivated fields, flowerbeds, andvegetable gardens. Black nightshade is found on avariety of soils from sandy/gravelly soils to fertilecultivated soils but seems to be adapted to soils that arehigh in nitrogen.

Distribution: Occurs infrequently in southern parts ofthe province (Douglas et al. 2000) but is present in the

Okanagan, Thompson, Mainland, Vancouver Island,and Peace River agricultural reporting regions. Notconsidered a major concern in the province.

Historical: Introduced from South America.

Life cycle: Germinates in spring and through thesummer. Flowering begins by mid-June, and the berriesmature 4–5 weeks later. Maximum flower initiationoccurs under full sunlight (Masset and Munro 1985).


Seed production: Capable of producing 2,500–5,000seeds/plant (Basset and Munro 1985).

Seed bank: Can remain viable for more than 5 years.

Dispersal: Berries and seed are dispersed by rodents,

birds, livestock, and humans and along watercourses.

Hybridization: May hybridize with other closelyrelated nightshades (Basset and Munro 1985).

Basset, I. J., and D. B. Munro. 1985. The biology ofCanadian weeds. 67. Solanum ptycanthum Dun., S.nigrum L., and S. sarrachoides Sendt. CanadianJournal of Plant Science 65: 401–414.

Douglas, G. W., D. Meidinger, and J. Pojar, eds. 2000.Illustrated Flora of British Columbia. Vol.5: Dicotyledons (Salicaceae throughZygophyllaceae) and Pteridophytes.Province of British Columbia.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Black nightshade. Weeds of the West. Western Societyof Weed Science, in cooperation with the WesternUnited States Land Grant Universities CooperativeExtension Services, Newark, CA.

Biocontrol: None.

Mechanical: Mowing and tillage over several yearsbefore seed-set may achieve eradication.


Herbicides: Post-emergence application of dicambaand glyphosate will provide control. Atrazine,cyanazine, and linuron have also been effective (Bassetand Munro 1985). Consult the most recent edition ofBC Ministry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Prevent the establishment of newinfestations by minimizing disturbance and eliminatingseed production and dispersal.


9

Integrated Management SummaryIntegrated management should focus oneliminating seed production and depleting theseed bank. Use mechanical or chemicalmethods to prevent seed production, and reviseland management practices to ensure themaintenance of a vigorous perennial plantcommunity.

Management ________________________________________

References __________________________________________


Growth form: Winterannual forb.

Flower: Flowersare small and bluish purple,have 4 petals, and areconnected by a stalk to arough central stem.

Seeds/Fruit: Fruits have aconspicuous beak, about one-third the length of the pod.These fruits break aparttransversely into numerous 2-seeded sections instead ofsplitting longitudinally as with mostmustards. Seeds are rectangular, with one flat side andone rounded side (Stubbendieck et al. 1995).

Leaves: Leaves are alternate and oblanceolate, withwavy or coarsely toothed margins, and arepartially covered with minute, gland-tipped hairs.

Stems: Mature plants are 10–50 cm tall,with branches that spread mainly fromthe base. Stems are partially coveredwith minute, gland-tipped hairs.

Roots: Shallow taproot.

Seedling: Seedlings form rosettes with deeply lobedleaves.

Other: Foliage has a disagreeable odour.

Similar Species

Exotics: None known.


Agricultural: Blue mustard invades disturbed habitatsand cultivated lands, reducing crop yields and affectingcrop quality (Whitson et al. 1996). It is a problem inwinter annual crops, such as winter wheat (Klein et al.1985). Blue mustard gives off a disagreeable odour

(like stale dishrags), and dairy animals eating it mayproduce off-flavour milk.


Human: None known.

BLUE MUSTARD

Chorispora tenella (Pallas) DC.Family: Brassicaceae (Mustard).


Other Common Names: Tenella mustard, purple mustard, crossflower, bean-podded mustard.



10

Impacts ____________________________________________


General requirements: Blue mustard is commonlyfound in dry areas such as grain fields, along roadsides,rights-of-way, and disturbed habitats. It can tolerate awide range of environmental conditions and soils.

Distribution: Blue mustard is frequent in the low-elevation areas of the BC Interior. It is also foundthroughout the western US.

Historical: Introduced from Siberia in 1929 (Klein etal. 1985).

Life cycle: Blue mustard seeds germinate in late

summer and autumn. The plant overwinters as arosette. The flower stalks usually bolt in March.Flowers appear in early April, and viable seeds can beproduced approximately 10 days after bloom (Klein etal. 1985).


Seed production: No information available.

Seed bank: No information available.

Dispersal: No information available.

Hybridization: No information available.

Klein, R. N., D. J. Lyon, and G. A. Wicks. 1985. Bluemustard control. NebGuide G95-1272-A. CooperativeExtension, University of Nebraska Institute ofAgriculture and Natural Resources.http://ianrwww.unl.edu/pubs/weeds/g1272.htm [26 Feb99].

Stubbendieck, J., G. Y. Friisoe, and M. R. Bolick.1995. Blue mustard. Weeds of Nebraska and the GreatPlains. Lincoln: Nebraska Department of Agriculture,Bureau of Plant Industry.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, and R. Parker. 1996.Blue mustard. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: None.

Mechanical: Small infestations can be pulled. Plantsare easy to pull in the spring before they flower andwhen soils tend to be soft and moist.


Herbicides: Metsulfuron-methyl provides excellentcontrol. Blue mustard can be controlled with dicamba,2,4-D, or glyphosate applied before plants bolt. Consultthe most recent edition of BC Ministry of Agriculture,Food and Fisheries Crop Production Guides forspecific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: In heavily infested crop fields,changing the crop rotation will help decrease the bluemustard population (Klein et al. 1985). In late spring

crops, blue mustard must be killed through tillage orwith a contact herbicide (Klein et al. 1985) beforeplanting.


11

Integrated Management SummaryControlling blue mustard can be challengingbecause the plant flowers early and herbicidesare often applied too late to be effective. Bluemustard should be controlled by preventingseed production until the soil seed bank isdepleted. Cut, pull, or treat plants withherbicide before seed-set.

Management ________________________________________

References __________________________________________


Growth form: Biennial forb.

Flower: Numerous flowers (10–20 mmlong) are arranged on the upper side of short

stems that elongate afterflowering (BC Ministry ofAgriculture and Fisheries1988). Buds are reddishpurple, becoming brightblue upon flowering.The petals are fused atthe base into a shorttube that flares at the topinto unequal lobes(Douglas et al. 1998).

Seeds/Fruit: Nutlets areclustered together ingroups of 4. Each nutlet(seed) is 3 mm long,greyish brown, angular,roughened, and wrinkled.

Leaves: Basal leaves arenarrow, 6–25 cm long, and have stalks. The alternate

stem leaves become progressively smaller and stalklessmoving up the stem. All leaves are covered with stiffhairs. The hairs are sometimes swollen at the base.

Stems: Stems are erect and covered with short hairsand scattered long, stiff hairs, and grow 30–80 cm tall.The long hairs often have swollen dark bases that formconspicuous flecks on the stems (Frankton andMulligan 1970).

Roots: Long, stout, and black taproots, with smallerfibrous lateral roots.

Seedling: The seed leaves (cotyledons) are 9–14 mmlong and 4–7 mm wide and are covered with fine,needle-like hairs (Royce and Dickinson 1999). Theplant produces a flat rosette with long, narrow leaves inthe first year.

Similar Species

Exotics: With its bright blue flowers and rough, hairyfoliage, this plant is not likely to be confused withother plants.


Agricultural: Usually not found in cultivated crops butcan invade rangelands and pastures. Seeds cancontaminate clover and other crop seeds and can act asan alternate host for viral diseases.

Ecological: This plant is generally unpalatable andincreases in overgrazed pastures. Competition withnative species in BC is unknown.

Human: None known.

BLUEWEED

Echium vulgare L.Family: Boraginaceae (Borage).


Other Common Names: Viper’s bugloss, blue devil.

Legal Status: Regional Noxious: Cariboo, Central Kootenay,Columbia-Shuswap, East Kootenay, Okanagan-Similkameen,Thompson-Nicola.


12

Impacts ____________________________________________


General requirements: Blueweed grows in dryroadsides, disturbed habitats, rocky pastures, andrangelands at low- to mid-elevations in BC. It is welladapted to dry, rocky, or shallow soils, especially overlimestone.

Distribution: Frequent in the central and south-centralareas of the province, it is also present on theMainland, Vancouver Island, and in northern parts(Douglas et al. 1998) and is considered a majorconcern in the Kootenay, Okanagan, Thompson, and

Cariboo agricultural reporting regions. It is found inevery Canadian province, and especially Ontario andQuebec (Frankton and Mulligan 1970).


Life cycle: Germinates in autumn and overwinters as arosette. In spring, the stems elongate and floweringbegins by late June to early July. Seeds ripen fromAugust to November, depending on geographiclocation (NS Department of Agriculture and Fisheries2001).


Seed production: A single plant may produce up to2,800 seeds.

Seed bank: Seeds can remain viable in the soil forseveral years.

Dispersal: Most seeds fall to the ground near theparent plant. The rough seeds stick to clothing, animalfur, and feathers. Dead flower stalks may break off andbe dispersed by the wind.


BC Ministry of Agriculture and Fisheries. 1988.Blueweed. Agdex 640 Fact Sheet.

Douglas, G. W., D. Meidinger, and J. Pojar. 1998.Illustrated Flora of British Columbia. Vol. 2:Dicotyledons (Balsaminaceae through Cuscutaceae).Province of British Columbia.

Frankton, C., and G. A. Mulligan. 1970.Weeds of Canada. Publication 948. Ottawa:Canada Department of Agriculture.

NS Department of Agriculture and Fisheries. 2001.Nova Scotia Noxious Weeds—Blueweed.http://www.gov.ns.ca/nsaf/rir/weeds/blueweed.htm[June 2001].

Royer, F., and R. Dickinson. 1999. Weeds of Canadaand the Northern United States. Edmonton: Universityof Alberta Press.

Biocontrol: None.

Mechanical: Cutting established blueweed can reduceseed production, but repeated treatments may berequired to prevent shoots from re-sprouting andproducing seed. Repeated defoliation will eventuallydeplete root reserves and reduce the plant’s capacity toflower (NS Department of Agriculture and Fisheries2001).


Herbicides: Spring or early autumn application of 2,4-D will manage blueweed. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Small infestations can bemanaged with hand-pulling.


13

Integrated Management SummaryIntegrated management can combine cultural,mechanical, and chemical treatments. Newinfestations can often be managed with hand-pulling. Seed disturbed areas to perennialgrasses and forbs, and manage grazing animalsto maintain perennial plant communities. Forlarger infestations, chemical management maybe required as well.

Management ________________________________________

References __________________________________________


Growth form: Denselytufted perennial, 30–60 cmin diameter.

Flower: Numerous small, non-showyflowers are produced in clusters 3–12cm long along one side of the stem.

Seeds/Fruit: Egg-shaped capsule2.0–2.5 mm long. The capsules containnumerous minute (0.5 mm) seeds(Douglas et al. 2001).

Leaves: The true leaves are basal andare reduced to short sheaths at the baseof the stem.

Stems: The stems, often mistaken forleaves, grow 0.3–1.3 m tall. They are

usually hollow, round, and smooth,but occasionally they are lined withmany fine ridges.

Roots: Stout, spreading rhizomes.


Similar Species


Natives: Bog rush is a native plant that may bedifficult to tell apart from other native rushes.Distinguishing characteristics of bog rush are its largesize, its habit of forming dense clumps, and theposition of the inflorescence at the side of the stem.

Agricultural: Troublesome on lowland pastures. Thisunpalatable plant for livestock can compete with hayand pasture crops, reducing pasture yields and carryingcapacity.

Ecological: Spreads and replaces other native speciesin disturbed, wet, poorly drained areas. It can become

dominant on overgrazed riparian sites.

Human: Used as a landscape ornamental for watergardens, where it is usually grown in submerged tubsto prevent invasive spread (Perry. Undated).

BOG RUSH

Juncus effusus L.Family: Juncaceae (Rush).


Other Common Names: Common rush, soft rush, swamp grass.



14

Impacts ____________________________________________


General requirements: Well adapted to wet, poorlydrained conditions, especially on muck soils and onriver shores that are periodically flooded. It tolerates8–13 cm of standing water, is adapted to acidicconditions, and requires open sunlight (Perry.Undated). In undisturbed conditions, it is found inshallow marshes, fresh meadows, and along the edgesof bogs. In disturbed conditions, it will disperse intowet to moist sites in pastures, fields, ditches, clearings,and forest margins. It is found at low- to mid-elevations in BC.

Distribution: Common in coastal areas of theprovince, but it also occurs in the southern Interior. Itgrows in temperate regions of North America andEurasia.

Historical: Native to BC.

Life cycle: A perennial plant that spreads outwardalong its rootstocks each growing season. It flowers inmidsummer.

Mode of reproduction: Spreads by seeds andrhizomes.


Seed bank: Seeds remain viable a long time, resultingin a large, persistent seed bank (Leck et al. 1989).

Dispersal: Seeds drop from the plant, but others aredispersed by water, wildlife, and livestock.


Douglas, G. W., D. Meidinger, and J. Pojar. 2001.Illustrated Flora of British Columbia. Vol. 6:Monocotyledons (Acoraceae through Najadaceae).Province of British Columbia.

Leck, M. A., V. T. Parker, R. L. Simpson. 1989.Ecology of Soil Seed Banks. San Diego, CA:

Academic Press.

Muenscher, W. C. 1980. Weeds. 2d ed. Ithaca, NY:Cornell University Press.

Perry, L. Undated. Juncus effusus. University ofVermont. http://pss.uvm.edu/pss123/adjunc.html

Biocontrol: None.

Mechanical: Tussocks can be grubbed out and thendeeply buried, or dried and burned. Once bog rush isremoved, the land should be cultivated for 1–2 yearsand then seeded to grass (Muenscher 1980).

Fire: Deeply buried rhizomes are not affected by fire.

Herbicides: Glyphosate and 2,4-D are effectiveapplied as either a wipe-on or a broadcast treatment.Use a surfactant with 2,4-D to help the herbicideadhere to the leaves. Consult the most recent edition ofBC Ministry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Drainage favours grasses andreduces bog rush on pastures. Maintain hay and grasscrops in high vigour to minimize bog rush invasion.

Avoid disturbance and graze riparian areas moderatelyto promote vigorous stands of sedges and otherdesirable vegetation.


15

Integrated Management SummaryTry to control water levels in pastures andhayfields to low levels that will reduceinvasion of bog rush. Manage pastures tomaintain a vigorous cover of perennial grassesand forbs that can compete with bog rush.Minimize disturbance and graze wet areasmoderately to promote vigorous stands ofnative or introduced vegetation that cancompete with bog rush.

Management ________________________________________

References __________________________________________



Flower: Flowers are 4–5 cm wideand clustered at the ends

of branches. The flower bractsare somewhat tapered andcovered with spines(Whitson et al. 1996).Flowers are pinkish to darkpurple, rarely white.

Seed/Fruit: Shiny light-brown seeds are capped witha circle of plume-like whitehairs.

Leaves: The alternate, deeply lobed leaves have stoutspines at the lobes and tips. The bases of the leavesclasp the stems with distinctive spiny wings.

Stems: The stems are erect and branched, with thebranches spreading upward. Plants range from 0.3 to2.0 m tall (Douglas et al. 1998).

Roots: A short, fleshy taproot with several primaryroots extending from the root crown. Each bears anumber of smaller lateral roots.

Seedlings: Seed leaves (cotyledons) are round tospatulate, and smooth. First true leaves are oval tospatulate with spines and a rough, bumpy surface(Carey et al. 1993). First-year plants form a rosette.

Similar Species

Exotics: Bull thistle is similar to other thistles(Carduus, Cirsium, and Onopordum genera) but can bedistinguished by flower size, bracts, and leaf surfaces.

Natives: Several species of Cirsium are native to BC,but the wavy-leaved thistle (Cirsium undulatum) ismost similar to bull thistle. Unlike bull thistle, wavy-leaved thistle has densely woolly and wingless stems(Frankton and Mulligan 1970).

Agricultural: Heavy infestations can exclude livestockfrom areas. Additionally, the presence of bull thistle inhay decreases forage value and lowers market price(Zimmerman 1997). It is an aggressive weed but willnot survive where cultivation has cut back its stem anddestroyed its root system (FEIS 1996).

Ecological: Bull thistle is often a transient species,appearing in recent clear-cuts or disturbed areas andbecoming a dominant species for several years (Rees etal. 1996).

Human: Reported to cause hay fever in someindividuals (FEIS 1996).

BULL THISTLE

Cirsium vulgare (Savi) TenoreFamily: Asteraceae (Sunflower).


Other Common Names: Common thistle, spear thistle, fuller’sthistle.



16

Impacts ____________________________________________


General requirements: Bull thistle grows in dry tomoist habitats that include roadsides, cultivated fields,pastures, and logged forestland and disturbed habitatsassociated with soil disturbance (Powell et al. 1994). Itgrows on a wide range of soil types, ranging fromgravelly to clay-textured. Bull thistle is generally

intolerant to shade and is nearly absent if light isreduced to less than 40% of full sunlight (FEIS 1996).

Distribution: Common throughout eastern Canada andthe US. It is widespread and locally abundant in allareas of BC (Powell et al. 1994) and is present in allagricultural reporting regions.

Historical: Introduced from Eurasia as a seedcontaminant.

Life cycle: Biennial, forming a rosette in the first yearand bolting in the second year (Frankton and Mulligan1970).


Seed production: Mature plants can produce up to4,000 seeds/plant (Zimmerman 1997).

Seed bank: Seeds are highly viable and usuallygerminate rapidly whenever conditions are favourablein spring and autumn (FEIS 1996). Seeds that areburied to 12 cm may remain viable for up to 3 years(Zimmerman 1997).

Dispersal: Seeds have a pappus and can be windblownfor long distances, but Zimmerman (1997) found that65% of the seeds land within 2 m of the parent plant.


Calweed Database. 1997. California Noxious WeedManagement Projects Inventory. Natural ResourceProjects Inventory, Information Center for theEnvironment, University of California, Davis.http://endeavor.des.ucdavis.edu/weeds/ [6 Jan 99].

Carey, J. B., J. J. Kells, and Karen A. Renner. 1993.Common weed seedlings of Michigan. Department ofCrop and Soil Sciences, Michigan State UniversityExtension. Bulletin E-1363.http://www.msue.msu.edu/msue/iac/e1363/e1363.htm[27 Oct 99].


FEIS—Fire Effects Information System. 1996.Prescribed Fire and Fire Effects Research Work Unit,Rocky Mountain Research Station (producer), US ForestService. http://www.fs.fed.us/database/feis/ [12 Mar 98].


Powell, G. W., A. Sturko, B. M. Wikeem, and P. Harris.1994. Field Guide to the Biological Management ofWeeds in British Columbia. Land ManagementHandbook No. 27. BC Ministry of Forests.

Rees, N. E., P. C. Quimby, Jr., G. L. Piper, E. M.Coombs, C. E. Turner, N. R. Spencer, and L. V.Knutson (eds.). 1996. Biological Management of Weedsin the West. Western Society of Weed Science, incooperation with USDA Agricultural Research Service,Montana Department of Agriculture, and MontanaState University.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996. Bullthistle. Weeds of the West. Western Society of WeedScience, in cooperation with the Western United StatesLand Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: Urophora stylata (seedhead fly), releasedin BC, can reduce seed production up to 80% in someareas (Zimmerman 1997).

Mechanical: Cutting and mowing topgrowth or cuttingthe taproot just below the root crown before seed-setwill eliminate annual seed production. Repeatedapplications of the treatment may be necessary. Cuttingand mowing treatments are most effective before theplant has bolted.


Herbicides: Picloram, dicamba, glyphosate, and 2,4-Dall provide effective management. Herbicides should beapplied in the rosette stage or after mowing as the plantbecomes more tolerant of herbicides once the flowerstalk is produced (FEIS 1996). Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, read

the label for full use and precautionary instructions.

Cultural/Preventive: Minimize disturbance andestablish stands of perennial grasses or forbs.


17

Integrated Management SummaryA combination of prevention, cultural control,and chemical control is probably the beststrategy for bull thistle. Reduce disturbancesand reseed areas already disturbed. Usebiocontrol agents if they are available. Do notuse chemical management if biocontrol agentshave been released unless the agent has not

established.

Management ________________________________________

References __________________________________________

Zimmerman, J. A. C. 1997. Ecology and distribution ofCirsium vulgare (Savi) Tneore, Asteranceae. USGSColorado Plateau Field Station, Southwest Exotic PlantMapping Program.http://www.usgs.nau.edu/swemp/Info_pages/plants/Cirsium/cvulgare.htm [29 Jan 99].


18


19



Flower: Flower heads arewhite to purple and borne in

clusters of 1–5/branch, with a strongvanilla scent. Heads are only about 1cm in diameter. Floral bracts arespineless.

Seeds/Fruit: One-seeded fruits(achenes) are straw or light brown incolour, straight or slightly curved (Moore1975).

Leaves: Leaves are spiny, alternate,oblong or lance-shaped, with thebase leaves stalkless andclasping, or extended downalong the stem.

Stems: Mature plants rangefrom 0.3 to 2.0 m in height.

Roots: Canada thistle has both horizontal and verticalroots. The horizontal roots produce numerous shoots,while vertical roots store water and nutrients in smallbranches.

Seedling: Early spring growth appears as rosettes withspiny-tipped, wavy leaves.

Similar Species

Exotics: Numerous introduced thistles are present inBC. Plumeless thistle (Carduus acanthoides) has floralbracts that are covered with sharp spines. Flowers tendto be solitary (Powell et al. 1994).

Natives: Wavyleaf thistle (Cirsium undulatum) is mostcommon on grassland and dry forests (Douglas et al.1998). Flower heads are usually large and the plantlooks more like bull thistle than Canada thistle.

Agricultural: Canada thistle infests crops, pastures,rangelands, roadsides, and riparian areas (Beck 1996).

Ecological: The plant spreads rapidly throughhorizontal roots (rhizomes) that give rise to shoots(Moore 1975). Its root system can be extensive,

growing up to 5.5 m in one season, but most oftenpatches spread about 1–2 m/year (Nuzzo 1998). Theplant can form dense patches and virtual monocultures.

Human: Thickets can restrict recreational access toinfested areas.

CANADA THISTLE

Cirsium arvense (L.) Scop.var. horridum Wimm. & Grab.Family: Asteraceae (Sunflower).


Other Common Names: Field thistle, Californian thistle.



20

Impacts ____________________________________________


General requirements: Canada thistle is adapted to awide range of soil types and environmental conditions(FEIS 1996). This weed occurs throughout theagricultural areas of all Canadian provinces (Franktonand Mulligan 1970) and over a wide range ofelevations and habitats in BC. Although it mainlyoccurs in disturbed areas, it invades native plantcommunities, meadows, wetlands, and forestedhabitats. It is best adapted to rich, heavy loam, clay

loam, and sandy loam, with an optimum soil depth of50 cm (FEIS 1996). Canada thistle can tolerate salinesoils (up to 2% salt) and a wide range of soil moistureconditions. The plant usually occurs in areas with45–90 cm annual precipitation or where supplementalsoil moisture is available (Beck 1996). It is alsosomewhat shade intolerant and can grow along theedge of forested areas, but is rarely found withinforests except in openings.

Distribution: Canada thistle is widespread in all areasof BC (Powell et al. 1994) on roadsides, cultivatedfields and pastures, and logged forests and otherdisturbed areas. It is present in all of the province’sagricultural reporting regions but is considered a majorconcern only in the Omineca and Peace River regions.

Historical: Introduced from Eurasia likely as acontaminant of crop seed as early as the late 18th

century.

Life cycle: Canada thistle is the only thistle with maleand female flowers on separate plants (Frankton andMulligan 1970). Female flowers can be distinguishedfrom male ones by the absence of pollen (abundant inmale flowers) and the presence of a distinct vanilla-likefragrance. Flowering occurs from June to October,depending on elevation and latitude, and seeds mature

from July to October. Large patches may contain onlymale plants and have no seed production. Roots andshoots develop during the winter and stems begin toelongate in early spring when temperatures reach about5° C and when daylight exceeds 14 hours (Nuzzo1998; Haderlie et al. 1991; FEIS 1996).

Mode of reproduction: By seed and vegetatively fromroots.

Seed production: Plants can produce up to 5,200 seedsannually but average about 1,500 seeds/plant (Rutledgeand McLendon. Undated).

Seed bank: Seeds usually germinate in mid-spring.Most seeds do not remain viable after 3 years.Dispersal: Primarily by wind.


Beck, K. G. 1996. Canada thistle. Colorado StateUniversity Cooperative Extension Natural ResourcesSeries, No. 3. 108.http://www.ext.colostate.edu/pubs/natres/03108.html[24 Jan 00].

Beck, K. G., and J. R. Sebastian. 2000. Combiningmowing and fall-applied herbicides to control Canadathistle (Cirsium arvense). Weed Technology. In press.


FEIS—Fire Effects Information System. 1996.Prescribed Fire and Fire Effects Research Work Unit,Rocky Mountain Research Station (producer), USForest Service. http://www.fs.fed.us/database/feis/ [12Mar 98].

Biocontrol: A number of agents have been released inBC with no success. The seed weevil Larinus planusand the stem gall fly Urophora carduii are beingredistributed. Localized attack by a non-specific rustfungus and aphid species is occasionally reported.

Mechanical: Repeated mowing can be effective inreducing seed-set. Intensive cultivation aimed atdepleting food reserves in the roots, followed bycompetitive cropping, is effective in the long term.


Herbicides: Numerous herbicides are registered forcontrol or suppression of Canada thistle. On pasturesand idle areas, spring and autumn applications ofclopyralid or a dicamba/2,4-D mix have been effectivewhen roots are actively growing. Clopyralid alone canbe applied in spring or autumn. Spring applicationsshould coincide with the rosette to bud stages. Springapplications of picloram have also been effective whenCanada thistle is in the pre-bud to early bud growthstages. Consult the most recent edition of BC Ministry

of Agriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Reduce the spread of Canadathistle seeds by always purchasing certified crop seed.Eliminate new seedlings before they form a well-developed root system.


21

Integrated Management SummaryThe tendency of this species to grow in wetareas may restrict the use of herbicides.Integrated management must involvecombinations of mowing, cultivation,herbicides, and competitive seeding to depletethe aggressive creeping root system.

Management ________________________________________

References __________________________________________


Haderlie, L. C., R. S. McAllister, R. H. Hoefer, P. W.Leino. 1991. Canada thistle control. In L. F James, J.O. Evans, M. H. Ralphs, and R. D. Child, eds. NoxiousRange Weeds. Boulder, CO: Westview Press.

Moore, R. J. 1975. The biology of Canadian weeds. 13.Cirsium arvense (L.) Scop. Canadian Journal of PlantScience 55: 1033–1048.

Nuzzo, V. 1998. Element stewardship abstract forCirsium arvense. The Nature Conservancy, WildlandWeeds Management and Research Program.http://tncweeds.ucdavis.edu/esadocs/cirsarve.html [16Oct 98].

Powell, G. W., A. Sturko, B. M. Wikeem, and P. Harris.1994. Field Guide to the Biological Management of

Weeds in British Columbia. Land ManagementHandbook No. 27. BC Ministry of Forests.

Rutledge, C. R., and T. McLendon. Undated. Anassessment of exotic plant species of Rocky MountainNational Park. Department of Rangeland EcosystemScience, Colorado State University. Northern PrairieWildlife Research Center Home Page.http://www.npwrc.usgs.gov/resource/othrdata/Explant/explant.htm [15 Dec 98].

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Canada thistle. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.


22


23


Growth form: Annualor winter annual grass.

Flower: Cheatgrasspanicles change colour fromgreen to purple to brown as theplant matures and eventuallydries. Branches are slender,drooping, hairy, flexuous, withup to 8 spikelets.

Seeds/Fruit: Spikelets includingawns are 2–5 cm long,nodding, with 2–8 florets.

Leaves: Leaves are light greenand hairy. Sheaths are fusedexcept near the node at thebottom of each sheath. Thelower sheaths areconspicuously hairy, while theupper sheaths are sometimessmooth.

Stems: Mature plants aregenerally 10–75 cm tall. Stemsare erect, slender, glabrous, orslightly hairy.

Roots: The finely dividedfibrous root system typicallyreaches a depth of about 30cm but can grow to 150 cmdeep in the field (Hironaka1961; Hulbert 1955).

Seedling: Distinguished byhairy leaf blades and sheaths.

Similar Species

Exotics: Similar to Japanesebrome (Bromus japonicus) andrye brome (Bromus secalinus).


Agricultural: Cheatgrass can be troublesome in winterwheat and other crops. Awns many injure livestock andanimals’ eyes and mouths, but the plant has goodspring forage values before seed-set (Stubbendieck etal. 1997).

Ecological: Can form dense stands on sites that werepreviously disturbed, especially overgrazed areas.

The plant competes effectively for moisture withclimax dominants such as bluebunch wheatgrass(Elymus spicatus) and can interrupt the rate ofsuccessional change from low stages of succession tohigher stages of succession for long periods of time(Harris 1967).


CHEATGRASS

Bromus tectorum L.Family: Poaceae (Grass).


Other Common Names: Downy brome, downy chess, early chess,drooping brome, downy cheat, slender chess, downy bromegrass,military grass, broncograss, Mormon oats.



24

Impacts ____________________________________________


General requirements: In BC, cheatgrass grows atlow- to mid-elevations at the coast, and in thegrasslands and dry forests of the Interior. It is commonin recently burned rangeland, winter crops, disturbedareas, abandoned fields, eroded areas, and overgrazed

grasslands (Upadhaya et al. 1986). It can invaderangelands that have never been grazed by livestock(Svejcar and Tausch 1991).

Distribution: Cheatgrass is common in southern partsbut rare elsewhere in the province (Douglas et al.

1990). It is present in all agricultural reporting regionsexcept the Peace River but is not considered a majorconcern in any region.

Historical: Introduced from Eurasia, possibly in shipballast. Found at Spences Bridge as early as 1890(Mosley et al. 1999).

Life cycle: A winter annual that can germinate inautumn or spring when soil moisture is adequate.Autumn-germinated plants will establish a root systemthat allows the plant to take early advantage of springmoisture. Seeds mature about 2 months later(Upadhaya et al. 1986; Stubbendieck et al. 1997).

Plant heads appear in late April to early May, followed

by flowering within a week, and seeds mature in mid-to late June (Upadhaya et al. 1986).


Seed production: Cheatgrass can produce up to 450kg seeds/ha, depending on plant density andenvironmental conditions (Upadhaya et al. 1986).

Seed bank: Generally a low retention of seeds in thesoil because of high germination rates.

Dispersal: Seeds are dispersed short distances bywind, but the awns can attach to fur or clothing.


Carpenter, A. T., and T. A. Murray. 1998. Elementstewardship abstract for Bromus tectorum. The NatureConservancy, Wildland Weeds Management andResearch Program.http://tncweeds.ucdavis.edu/esadocs/bromtect.html

Douglas, B. J., A. G. Thomas, and D. A. Derksen.1990. Downy brome (Bromus tectorum) invasion intosouthwestern Saskatchewan. Canadian Journal ofPlant Science 70: 1143–1151.


Harris, G. 1967. Some competitive relationshipsbetween Agropyron spicatum and Bromus tectorum.Ecological Monographs 37: 89–111.

Hironaka, M. 1961. The relative rate of rootdevelopment of cheatgrass and medusahead. Journal ofRange Management 14: 263–267.

Biocontrol: None. Controlled livestock grazing canhelp regulate cheatgrass populations, but grazingprescriptions depend on the mixture of plants in theplant community.

Mechanical: Ponzetti (1997) reported that repeatedmowing every 3 weeks during spring and summer wasas effective at managing seed production, but thismethod was labour-intensive and expensive.

Fire: Fire has been effective in the US if plants areburned after they have dried but before the seeds havedropped (Carpenter and Murray 1998). Some seedswill survive, and if a fire is not repeated within 3–4years it is likely the population will re-establish.

Herbicides: Spring applications of quizalofop,fluazifop-p-butyl, sethoxydim, and glyphosate havesuccessfully controlled cheatgrass on various rangelandsites in the US. Management was usually best when theplants were less than 10 cm tall and growingvigorously (Wiese et al. 1995). Autumn applicationsare generally used in cropland situations by farmersgrowing winter wheat or other cool-season crops.Consult the most recent edition of BC Ministry of

Agriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Prevent new infestations byminimizing disturbance and seed dispersal andmaintaining vigorous perennial plant communities.Hand-pulling can be effective for a small infestation,especially before the plants set seed. On largerinfestations, hand-pulling may be required for severalyears until the seed bank is depleted. Seed disturbedareas to perennial grasses to provide competition.


25

Integrated Management SummaryIntegrated management will require acombination of chemical control, culturalcontrol, seeding perennial grasses, and properlivestock management where land is grazed.

Management ________________________________________

References __________________________________________


26

Hulbert, L. C. 1955. Ecological studies of Bromustectorum and other annual bromegrasses. EcologicalMonographs 25: 181–213.

Melgoza, G., R. S. Nowak, and R. J. Tausch. 1990. Soilwater exploration after fire: Competition betweenBromus tectorum and two native species. Oecologia83: 7–13.

Mosely, J. C. 1996. Prescribed sheep grazing tosuppress cheatgrass: A review. Sheep and GoatResearch Journal 12: 74–81.

Mosely, J. C., S. C. Bunting, and M. E. Monoukian.1999. Cheatgrass. In R. L. Sheley and J. K. Petroff,eds. Biology and Management of Noxious RangelandWeeds. Corvallis: Oregon State University Press.

Ponzetti, J. M. 1997. Assessment of medusahead andcheatgrass control techniques at Lawrence. MemorialGrassland Preserve 1996 Annual Report. The NatureConservancy of Oregon.

Rice, K. J., and R. N. Mack. 1991. Ecological geneticsof Bromus tectorum: Intraspecific variation inphenotypic plasticity. Oecologia 88: 84–90.

Stubbendieck, J., S. L. Hatch, and C. H. Butterfield.1997. North American Range Plants. Lincoln:University of Nebraska Press.

Svejcar, T., and R. Tausch. 1991. Anako Island,Nevada: A relict area dominated by annual invaderspecies. Rangelands 13: 233–236.

Upadhaya, M. K., R. Turkington, and D. McIlvride.1986. The biology of Canadian weeds. 75. Bromustectorum L. Canadian Journal of Plant Science 66:689–709.

West, N. E. (ed.). 1983. Western intermountainsagebrush steppe. Temperate Deserts and Semi-Deserts. Amsterdam, Neth.: Elsevier ScientificPublishing Company.

Whitson, T. D., and D. W. Koch. 1998. Control ofdowny brome (Bromus tectorum) with herbicides andperennial grass competition. Weed Technology 12:391–396.

Wiese, A. F., C. D. Salisbury, and B. W. Bean. 1995.Downy brome (Bromus tectorum), jointed goatgrass(Aegilops cylindrica), and horseweed (Conyzacanadensis) control in fallow. Weed Technology 9:249–254.

Young, J. A., and R. A. Evans. 1985. Demography ofBromus tectorum in Artemisia communities. In J.White, ed. The Population Structure of Vegetation.Dordrecht, Neth.: Dr. W. Junk Publishers.


27


Growth form: Perennialforb.

Flower: Flowers are bornein the axils of the upper leaves.Flowers are 4 cm in diameter,usually blue, but occasionally purpleor white.

Seeds/Fruit: Fruits areribbed and tipped by acrown of minute scales.

Leaves: Basal leavesare rough, 8–25 cmlong, lance-shaped,toothed or pinnately parted.

Upper leaves are smaller, alternate, stalkless, claspingthe stem, with undivided margins.

Stems: Mature plants range in size from 0.3 to 2.0 mtall. Stems are erect and branched above. The entireplant exudes a milky juice when broken.

Roots: Plants grow from a deep taproot.


Similar Species


Natives: Chicory can be distinguishedfrom blue lettuce (Lactuca tatarica) by itsmore branched growth pattern andstalkless flowers.

Agricultural: Although this plant is grown as a haycrop in Europe, dairy products from cows that eat itmay taste bitter (Stubbendieck et al. 1995).

Ecological: In BC chicory invades disturbed areas and

native plant communities, but its impacts have not beendocumented.

Human: Milky latex may cause dermatitis.

CHICORY

Cichorium intybus L.Family: Asteraceae (Sunflower).


Other Common Names: Coffeeweed, blue sailors, succory.



28

Impacts ____________________________________________


General requirements: Chicory is found from low- tomid-elevations at the coast and on Interior grasslandsand forests. It frequents roadsides, fields, and disturbedhabitats. It can adapt to a wide range of soils andenvironmental conditions but often occurs on high-limesoils.

Distribution: Chicory occurs frequently in southernareas of the province and is common throughout NorthAmerica. It is present in the Kootenay, Okanagan,Thompson, Mainland, Vancouver Island, Cariboo, andOmineca agricultural reporting regions.

Historical: Introduced from Eurasia. Often planted foruse as salad greens, and the root is used as a substitutefor coffee (Whitson et al. 1996).

Life cycle: Flowering occurs from July to September,depending on location.

Mode of reproduction: By seeds.





Dow AgroSciences. 1998. Chicory—biennials/perennials. Dow AgroSciences. The Ranch,Pasture Improvement.http://www.dowagro.com/theranch/weeds.asp [5 Mar99].

Stubbendieck, J., G. Y. Friisoe, and M. R. Bolick.1995. Scotch thistle. Weeds of Nebraska and the GreatPlains. Lincoln: Nebraska Department of Agriculture,Bureau of Plant Industry.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Chicory. Weeds of the West. Western Society of WeedScience, in cooperation with the Western United StatesLand Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: None.

Mechanical: Chicory can be managed by mowing andcutting before plants set seed. Repeated treatments maybe required over several years to exhaust nutrientreserves in the roots and to control new plants thatemerge from the soil seed bank.


Herbicides: A combination of picloram and 2,4-D canbe effective when plants are actively growing (DowAgroSciences 1998). Combinations of dicamba, 2,4-D,and picloram or dicamba, 2,4-D, and glyphosate havealso been used to control chicory (Dow AgroSciences1998). Consult the most recent edition of BC Ministryof Agriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Prevent the establishment of newinfestations by minimizing disturbance and seeddispersal. Hand-pulling plants before seed-set can beeffective on new and small infestations, especiallybefore a seed bank has become established.


29

Integrated Management SummaryMaintaining healthy plant communities and re-vegetating disturbed areas prevent the spreadof chicory. Combine preventive measures withmechanical and chemical control. Useherbicides with cultural methods whereappropriate, especially on new infestations.

Management ________________________________________

References __________________________________________


Growth form: Annualforb.

Flower: Saucer-likeflowers are stalked and arise inclusters of 3–5 from branchlets inmost leaf axils. Flowers arewhite, 1.6–2.0 mm wide, with 4lobes.

Seeds/Fruit: Nutlets are inpairs, 3–5 mm wide,covered in short,hooked hairs.

Leaves: The fewbasal leaves soonwither. The narrowstem leaves, 1–4 cmlong, are in whorls of 8 (sometimes 6).Leaves have pointed tips and are coveredwith bristly, hooked hairs.

Stems: Solitary stems are weak with few branches andmay be climbing or prostate, 10–100 cm long. Stemsare square with short, backward-pointing hairs at thebase of each leaf.

Roots: Annual taproot.

Seedling: The cotyledons (seed leaves) are roundedwith a notch at the tip. The first leaves appear in awhorl of 4 and have spines on the tips(Royer and Dickinson 1999).

Similar Species

Exotics: False cleavers (Galiumspurium) closely resembles cleavers,but it has smaller (1.0–1.5 mm wide), greenish creamflowers with smaller nutlets (1.5–3.0 mm long).

Natives: Seven Galium species are native to BC, andall have square stems with leaves in whorls. Only one,Galium bifolium, is an annual, and its leaves are inwhorls of 4 instead of 8.

Agricultural: Problematic in forage, grain, and canolacrops. It is a competitive plant that reduces yield,becomes entangled in harvesting equipment, andreduces the quality and value of crop seed. It is acontaminant in canola, where it reduces the value ofthe seed and reduces the quality of the pressed oil.

Ecological: Occurs in non-cultivated areas such asfields, thickets, open forests, and rocky bluffs. Cleaversclings to other plants while it competes for light,moisture, and nutrients.

Human: Fruits are used as a coffee substitute.

CLEAVERS

Galium aparine L.Family: Rubiaceae (Bedstraw).


Other Common Names: Bedstraw, white hedge.

Legal Status: Regional Noxious: Peace River.


30

Impacts ____________________________________________


General requirements: In BC, found in moderatelydry to moist fields, lawns, gardens, disturbed areas,beaches, and open forests at low- to mid-elevations(Douglas et al. 1999). Adapted to damp, moist soil(Alberta Agriculture 1983).

Distribution: Found in all areas of the province but

considered a major concern in the Peace River region.


Life cycle: An annual plant that usually completes itslife cycle in one year but can overwinter and grow as awinter annual. Most seedlings emerge in mid-spring,but seeds continue to germinate through the summer.

Plants flower from June through August, and seed isproduced from August until frost (Alberta Agriculture2001).


Seed production: A single plant can produce 3,500seeds (Alberta Agriculture 2001).

Seed bank: Seed can remain viable up to 6 years.

Dispersal: Cleavers seeds are similar in size and shapeto canola seed and cannot be easily separatedmechanically. Planting contaminated canola is the mainsource for spread, but harvesting equipment, animals,humans, and contaminated animal manure can alsodisperse the seeds.

Hybridization: Little evidence.

Alberta Agriculture. 1983. Weeds of Alberta. Agdex640-4.

Alberta Agriculture. 2001. Cleavers.http://www.agric.gov.ab.ca/pests/weeds/64010030.html

Douglas, G. W., D. Meidinger, and J. Pojar. 1999.Illustrated Flora of British Columbia. Vol. 4:Dicotyledons (Orobanchaceae through Rubiaceae).Province of British Columbia.

Malik, N., and W. H. Vanden Born. 1988. The biologyof Canadian weeds. 86. Galium aparine L. and Galiumspurium L. Canadian Journal of Plant Science 68:481–499.


Biocontrol: None.

Mechanical: Tillage can manage emerging seedlings atpre-seeding, post-seeding, in the autumn, or onsummerfallow. Tillage at some stages may encourageweed germination, so a second cultivation may berequired. Tilling on summerfallow can prevent seedproduction and is most effective under warm, dryconditions so the plants cannot re-root. Mowing willnot control cleavers because of the plant’s prostrategrowth habit.

Fire: Not managed by fire.

Herbicides: Many herbicides and herbicide mixes areused to manage cleavers in cereal crops. Herbicides arealso available for control in canola varieties resistant tospecific herbicides such as glyphosate, glufosinateammonium, and imazethapyr. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specific

recommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Rotations that includesummerfallow, cereals, or annual and perennial foragescan effectively manage cleavers populations (AlbertaAgriculture 2001). Planting with certified weed-freeseed, cleaning farm equipment, and compostingmanure before spreading also will reduce spread.


31

Integrated Management SummaryManage cleavers for prevention and earlycontrol and eradication. Use certified weed-free seed. Till soils to manage emergingseedling and spray appropriate herbicides asrequired.

Management ________________________________________

References __________________________________________

General requirements: Coast tarweed occurs alongdry roadsides and in disturbed areas (Douglas et al.1998). In other areas it is also found on dry hillsidesand overgrazed rangeland (Whitson et al. 1996).

Distribution: Coast tarweed occurs infrequently insouthern BC at low elevations (Douglas et al. 1998). It ispresent in the Kootenay, Thompson, Mainland, VancouverIsland, Cariboo, and Omineca agricultural reportingregions. Outside BC the plant is found from Washingtonto California (Whitson et al. 1996; Zardini 1992).

Historical: Possibly introduced from South America.

Life cycle: Annual or occasionally biennial. Coasttarweed is a self-compatible plant capable of rapidlyestablishing in disturbed areas.

Seed production: Prolific seed producer.


Dispersal: Nso information available.


Habitat and Ecology ______________________________


Flower: Flowering headsare partially enclosed by

leaves and clustered at the apex of thestem, at the ends of branches, andin the leaf axils.

Seeds/Fruit: Seeds areslender, light grey,grey, or black.

Leaves: Leaves arealternate, narrow,and lance-shaped.

Stems: Matureplants are 0.2–1.0m tall. Stems areerect, leafy, simple,or branching.

Roots: Taproot.


Other: The entire plant is sticky andhairy and has a disagreeable odour.It is called tarweed due to its sticky,glandular texture.

Similar Species

Exotics: Six tarweed species occur inBC, but it is not clear which areintroduced or native (Douglas et al.1998).

Natives: Clustered tarweed (Madia glomerata) iscommon to dry roadsides, meadows, and open slopesand is scattered throughout southern BC (Douglas et al.1998).

Agricultural: No information available.

Ecological: Coast tarweed is self-compatible, whichfacilitates its establishment and spread (Zardini 1992).


COAST TARWEED

Madia sativa MolinaFamily: Asteraceae (Sunflower).


Other Common Names: Chilean tarweed.



32

Impacts ____________________________________________



Scmeda-Hirschman, G. 1995. Madia sativa, a potentialoil crop of central Chile. Economic Botany 49:257–259.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Coast tarweed. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

Zardini, E. 1992. Madia sativa Mol. (Asteracea-Heliantheae-Madinae): An ethnobotanical andgeographical disjunct. Economic Botany 46: 34–44.

Biocontrol: None.

Mechanical: Pull or cut before seed-set.


Herbicides: No information available. Consult themost recent edition of BC Ministry of Agriculture,Food and Fisheries Crop Production Guides forspecific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Prevent the establishment of newinfestations by minimizing disturbance, eliminating

seed production, and maintaining healthy native plantcommunities.


33

Integrated Management SummaryCut/pull or treat plants with herbicide beforethey set seed. Manage new infestationsimmediately to ensure that seeds are not beingintroduced into the environment.

Management ________________________________________

References __________________________________________

General requirements: Commonly found on dry,fertile, lime-free, well-drained soils. It frequentlyoccurs on warm, sandy, and gravelly glacial out-washsoils (BC Ministry of Agriculture and Food. Undated).Found on roadsides, dry fields, pastures, and disturbedareas in BC.

Distribution: Common bugloss occurs only rarely insouth-central BC and southern Vancouver Island. Thelargest infestations are near Rock Creek and theRutland-Black Mountain area near Kelowna, and othersightings have been noted in the south Okanagan andKeremeos areas. It is also found in northern Washington.


Growth form: Biennial or perennial forb.

Flower: The inflorescence is a coiledcluster located at the end of the

stalk. The coil gradually straightensas the flower buds open.The tubular flowers areinitially reddish buteventually turn deeppurplish blue withwhite centres.

Seeds/Fruit: Eachflower produces acluster of 4 barblessnutlets. The nutlets aresquat and asymmetric or conical.

Leaves: Basal and lower leaves arestalked and lance-shaped, 6–20 cmlong and 1.0–5.0 cm wide (Douglas et al.1998). The stem leaves become graduallysmaller upward and lack stalks. The leaves are

succulent and covered with stiff hairs (BC Ministry ofAgriculture and Food. Undated).

Stems: Plants often have several stems andgrow 30–80 cm tall. The angular stemsare covered with spreading hairs.

Roots: Long taproot.


Similar Species

Exotics: European bugloss (Anchusa arvensis) andItalian bugloss (Anchusa azurea) also occur in BC, butthey have very limited distribution and only a fewspecimens have been found. Common hound’s-tongue(Cynoglossum officinale) has a similar appearance, butit has only a single stem per plant, the inflorescencesdo not uncoil, and the nutlets are strongly barbed.

Natives: Northern hound’s-tongue (Cynoglossumboreale) also resembles common bugloss, but it hasmore leaves that are rounded, the inflorescences do notuncoil, and the nutlets are barbed.

Agricultural: This weed invades pastures and haylands, where it reduces carrying capacity and yield. Itcauses spoilage in baled alfalfa hay because thesucculent leaves and stems become mouldy. Commonbugloss is not a problem in cultivated crops.

Ecological: Invades rangelands and disturbed areaswhere competing vegetation is sparse.


COMMON BUGLOSS

Anchusa officinalis L.Family: Boraginaceae (Borage).


Other Common Names: Common alkanet.

Legal Status: Regional Noxious: Kootenay/Boundary.


34

Impacts ____________________________________________


BC Ministry of Agriculture and Food. Undated. WeedAlert. Common Bugloss.

Douglas, G. W., D. Meidinger, and J. Pojar. 1998.Illustrated Flora of British Columbia. Vol. 2:

Gymnosperms and Dicotyledons (Balsaminaceaethrough Cuscutaceae). Province of British Columbia.

Biocontrol: None.

Mechanical: Cutting or mowing before plants flowerwill prevent seed production. Flowering stalks shouldbe bagged, removed from the site, and burned.

Fire: Fire can destroy above-ground parts of the plantbut will not affect the deep taproot and seeds in theseed bank.

Herbicides: No specific recommendations. Consultthe most recent edition of BC Ministry of Agriculture,Food and Fisheries Crop Production Guides forspecific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Small populations could behand-pulled. Pulling is easier in young plants beforethe deep taproot has developed. Monitor disturbedsites, especially on sandy or gravelly areas, for newoutbreaks. Inspect purchased hays and monitor stockfeeding areas. Remove any new infestations

immediately by pulling or cutting, and destroy anyflowering stalks. Clean equipment, vehicles, andfootwear before leaving an infested area. Maintaining astrong population of native perennials is the best wayto prevent the establishment of common bugloss.


35

Integrated Management SummaryEarly detection is important because this planthas a limited distribution in BC. Hand-pullplants and remove from the site before a seedbank can establish. Seed disturbed areas toperennial grasses and forbs to provide coverand competition against common bugloss.Manage grazing animals to maintain perennialplant communities.


Life cycle: This perennial forms a rosette of basalleaves in its first year. A single flowering stalk isformed in the second year and multiple stalks appear insubsequent years.

Mode of reproduction: Primarily by seed but rootfragments will re-sprout.

Seed production: A single plant can produces about900 seeds annually.


Dispersal: Ingestion of seeds by animals and seed-bearing stalks being tumbled in the wind. Vehicles,animal and human feet, redistribution of soils andgravels, and contaminated hay.

Hybridization: None known.

References __________________________________________

Management ________________________________________


Flower: Flowers are purple, less than 2.5cm across, and borne in short-stalked

clusters along the stems.

Seeds/Fruit: Mature flower heads form a prickly burthat readily sticksto clothing oranimals.

Leaves: Stemleaves arealternate,broadest at theleaf base, andsomewhatdiminishedupward. Lower leafstalks arehollow. Leafmargins aretoothed or wavy,and the entire leafis woolly beneathand dark green

above. Rosette leaves are large, hairy, and heart-shaped.

Stems: Mature plants are 1–3 m tall. The stem is erect,coarse, and much branched.

Roots: Large, fleshy taproot.

Seedling: Leaves of the rosette stage are large, simple,and usually heart-shaped (Stubbendieck et al. 1995).

Similar Species

Exotics: Great burdock(Arctium lappa L.) is alsolisted as a regional noxiousweed. Unlike commonburdock, it has solid lowerleaf stalks. Also, great burdockhas individual flowers larger than 2.5cm across, that are borne on long stalks and form aflat-topped cluster. Great burdock is quite rare insouthern BC and is found on dry roadsides, disturbedareas, and pastures of low- to mid-elevations.Cocklebur (Xanthium strumarium) has smaller, spiny-margined leaves.


Agricultural: Common burdock is not considered aproblem in crops since it is intolerant to cultivation.Livestock are fond of common burdock, and the foliageimparts a bitter taste to the milk if it is eaten in largequantities. Common burdock burs can becomeentangled in the hair of sheep, damaging the qualityand reducing the value of the wool.

Ecological: Due to its biennial nature, commonburdock is confined to areas that are not severelydisturbed on an annual basis.

Human: Because of its diuretic effects, commonburdock has been listed as a poisonous plant (Gross etal. 1980).

COMMON BURDOCK

Arctium minus L.Family: Asteraceae (Sunflower).


Other Common Names: Lesser burdock, wild burdock, bardane,wild rhubarb, beggars button.

Legal Status: Regional Noxious: Bulkley-Nechako, Cariboo,Columbia-Shuswap, Fraser-Fort George, Kitimat-Stikine, NorthOkanagan, Okanagan-Similkameen, Peace River, Thompson-Nicola.


36

Impacts ____________________________________________


General requirements: Common burdock is found atlow- to mid-elevations in grasslands and forests. It cancommonly be found growing along roadsides, ditches,stream banks, pastures, and disturbed habitats. It oftenoccurs in riparian areas that have moist, fertile soilswith high nitrogen contents.

Distribution: Established throughout much of Canadaand the US. It is frequent in coastal, west-central, andsouthern BC from low- to mid-elevations (Douglas etal. 1998). Burdock is a major concern in the Okanagan,Thompson, Cariboo, Omineca, and Peace regions, andis present in the Kootenay, Mainland, and VancouverIsland agricultural reporting regions.

Historical: Introduced from Eurasia.

Life cycle: Germination occurs mainly in early spring(Gross et al. 1980). During the first year, the plant

forms a rosette. The following year the plant producesa stout, grooved, rough stem with numerous branches.Flowering and seed production occur from July toSeptember. Seeds are mature by September, dependingon location, and are shed continuously throughout theautumn, winter, and following spring.


Seed production: Common burdock typicallyproduces 6,000–16,000 seeds/plant.


Dispersal: Bur-like seed heads are readily dispersed byattaching to animal fur or clothing.

Hybridization: Possibly hybridize with other Arctiumspecies.


Gross, R. S., P. A. Werner, and W. Hawthorn. 1980.The biology of Canadian weeds. 38. Arctium minus(Hill) Bernh. and A. lappa L. Canadian Journal ofPlant Science 60: 621–634.

Stubbendieck, J., G. Y. Friisoe, and M. R. Bolick.1995. Common burdock. Weeds of Nebraska and theGreat Plains. Lincoln: Nebraska Department ofAgriculture, Bureau of Plant Industry.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Common burdock. Weeds of the West. Western Societyof Weed Science, in cooperationwith the Western United StatesLand Grant UniversitiesCooperative Extension Services,Newark, CA.

Biocontrol: None.

Mechanical: Tillage can be used to kill the plants atthe rosette stage. Mowing or cutting can be used toeliminate seed production. Mow after the plant hasbolted but before it has flowered.


Herbicides: Common burdock can be controlled with2,4-D, picloram, dicamba, or glyphosate. Herbicidesare most effective when applied to first-year rosettes.Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Prevent the establishment of new

infestations by minimizing disturbance and seeddispersal, eliminating seed production, and maintaininghealthy native communities.


37

Integrated Management SummaryAs with other plants that reproduce solely byseed, integrated management efforts mustinclude the elimination of seed production andthe depletion of the seed bank. Combineherbicide or tillage treatment of rosettes withremoval of seed heads from any plants thathave bolted. Preventing dispersal of burs isparticularly important.


Management ________________________________________

References __________________________________________


Growth form: Annual to winter annualforb.

Flower: The stalked flowers arise eithersingly from the leaf axils or in small clusters at the endof the stems. The small (6 mm across), white,star-shaped flowers have 5 petals so deeplycleft they appear as 10.

Seeds/Fruit: The 4–5 mm longcapsules are egg-shaped and strawcoloured andcontain manytiny reddishbrown seeds0.9–1.3 mm long.

Leaves: Basalleaves areabsent. Thefleshy stemleaves are opposite, oval, entire, andcovered in hairs. The lower leaves arestalked, but the upper leaves are stalkless.

Stems: Stems usually are prostrate but may be upright.They are much branched and round in cross-sectionand have a conspicuous line of hairs on one side. Stemsfrequently root at the swollen nodes.

Roots: Roots are a slender rhizome that break easilywhen pulled.

Seedling: Seedlings have opposite, fleshy leaves thatare oval with pointed tips. The first pair of leaves has afringe of white hairs on the stalk (Royer and Dickinson1999).

Similar Species

Exotics: Grass-leaved starwort (Stellaria graminea) isfound in the province, but common chickweed isdistinguished by its broad leaves and line of hairs onone side of the stem. Mouse-ear, or field chickweed(Cerastium arvense), is a similar mat-forming weed,but it is a much hairier plant.

Natives: There are a number of native starworts(Stellaria sp.), but none have the line of hairs on oneside of the stem.

Agricultural: This is a problematic weed in cultivatedcrops, gardens, and lawns. Its early, rapid springgrowth can smother seedling crops, while its shadetolerance allows it to persist in tall crops, such ascereals. The succulent leaves remain green after cuttingand tangle on moving parts of harvest equipment.Detached chickweed plants can re-sprout, and duringcool, wet weather the mats will grow on harvested

swaths, delaying harvesting and complicating pickup(Alberta Agriculture 1995).

Ecological: Not competitive in established plantcommunities, though under cool, moist conditions itcan establish on disturbed sites.


COMMON CHICKWEED

Stellaria media (L.) Vill.Family: Caryophyllaceae (Pink).


Other Common Names: Common starwort.



38

Impacts ____________________________________________


General requirements: Chickweed is shade tolerantand well adapted to fertile soils and moist, coolgrowing conditions. In BC, it grows in grain fields,

cultivated fields, pastures, gardens, and disturbedhabitats at low- to mid-elevations.

Distribution: Chickweed is present in all agricultural

reporting regions of the province. It is found acrossCanada and in much of the world (Frankton andMulligan 1970).


Life cycle: Chickweed can germinate in both springand autumn, although the winter annual form occursonly in mild climates. Plants grow quickly and beginflowering 4–5 weeks after emergence. The plant mayalso germinate throughout the growing season ifweather conditions are favourable (Alberta Agriculture1995).

Mode of reproduction: Mainly by seed, but plants canroot at the nodes of the stems in moist, loose soil.

Seed production: Flowering continues over a longtime and seeds mature quickly after flowering. A singleplant can produce 15,000 seeds in a growing season(Cranston et al. 2000).

Seed bank: Seeds are immediately viable. Most seedsgerminate within 3 years, but 30% are viable after 10years (Royer and Dickinson 1999). Seeds require lightto germinate, and deeply buried seeds can survive up to60 years (Alberta Agriculture 1995).

Dispersal: Seeds can be transported on farmequipment and by contaminated soils. Ingested seedscan also be dispersed in animal manure.


Alberta Agriculture. 1995. Chickweed.http://www.agric.gov.ab.ca/pests/weeds/64010020.html

Cranston, R., D. Ralph, and B. Wikeem. 2000. FieldGuide to Noxious and Other Selected Weeds of BritishColumbia. BC Ministry of Agriculture, Food andFisheries and Ministry of Forests.

Douglas, G. W., G. B. Straley, D. Meidinger, and J.Pojar. 1998. Illustrated Flora of British Columbia. Vol.2: Dicotyledons (Balsaminaceae through Cuscutaceae).Province of British Columbia.

Frankton, C., and G. Mulligan. 1970. Weeds ofCanada. Publication 948. Ottawa: Canada Departmentof Agriculture.

Royer, F., and R. Dickinson. 1999. Weeds of Canadaand the Northern United States.Edmonton: University ofAlberta Press.

Biocontrol: None.

Mechanical: Tillage can manage chickweedeffectively, but different approaches are required fordifferent situations. Shallow tillage is recommended inspring to encourage weed growth. It should befollowed by a second tillage to remove the weedseedlings before seed-set. Autumn tillage will preventseed production and overwintering, but plants shouldbe deeply buried in the soil. Mowing is generallyineffective because the stems are so prostrate manyflowers will be missed.


Herbicides: Numerous herbicides can be used tomanage this plant. Consult the most recent edition ofBC Ministry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Common chickweed cannotcompete with vigorous plant stands. Strong perennialcrops can be used in rotation to suppress chickweed.

Vigorous annual crops can be produced by increasingseeding rates and by delaying seeding until emergingchickweed is managed. Similarly, thoroughsummerfallowing (spring and autumn) with repeated,deep tillage will give annual crops a competitiveadvantage.


39

Integrated Management SummaryChickweed infestations can be prevented ormanaged by maintaining competitive crops orperennial native plant communities.Management is achieved in establishedpopulations by stopping seed production andpreventing plants from re-establishing aftertillage. In temperate climates, where this weedis a winter annual, plant establishment andautumn seed production should be prevented.

Management ________________________________________

References __________________________________________

Growth form:Annual forb.

Flower: Oneor more rose to purpleflower heads about 1.3cm long, located at theend of each branch(Thill et al. 1999).

Seeds/Fruit: The black tosilvery beige seeds are0.3–0.6 mm long, coneshaped, covered withfine hairs, and taper to ablunt point. A pappusof 0.6-cm-long barbedhairs surrounds thewide end of the seed.

Leaves: Young plantsbegin with smoothbasal leaves butbecome toothed,then lobed, then finelydissected as the plantdevelops. Basal leavescan be 7.5 cm long. Thealternate stem leaves havefinely divided leaflets.

Older leaves become prickly as stiff hairs develop(Thill et al. 1999).

Stems: Mature plants are 0.2–0.9 mtall and usually produce a singlestem. Five to 15 branches will formnear the top under good growingconditions, but if the plant iscrowded or growing under poorconditions only 1–3 brancheswill form.

Roots: A short taproot.

Seedling: Seedlings have 2 fleshy,stalkless cotyledons 1.3–2.5 cm long,with prominent red or purple mid-veins.

Similar Species

Exotics: There are 2 varieties ofcommon crupina (Crupina vulgaris var.typica and var. brachypappa) present inNorth America. Common crupina var. brachypappa isdistinguished from var. typica by the large number ofstem leaves (about 40), larger seeds, and longer pappusbristles. Both varieties are considered noxious in theUS. Common crupina seedlings are similar to those ofknapweeds (Centaurea sp.). Crupina can be identifiedby the fleshy cotyledons and the prominent mid-vein.


Agricultural: Invades hayfields and grass seed fields.Common crupina seed can contaminate hay and otherforage crops, reducing their value.

Ecological: Infests disturbed grasslands and open

forest sites, where it can form dense stands andcompete with native plant species.

Human: None known.

COMMON CRUPINA

Crupina vulgaris Cass.Family: Asteraceae (Sunflower).


Other Common Names: None.



40

Impacts ____________________________________________


General requirements: Adapted to a wide range ofconditions. Usually found on well-drained sandy orloamy soil, where annual precipitation varies from 40to 75 cm, and at elevations of 300–975 m.

Distribution: Does not occur in BC. Presently, itoccupies areas of Washington, Oregon, Idaho, andCalifornia.


Life cycle: This winter annual usually germinates inlate summer or autumn, but it can germinate in spring.Plants overwinter as rosettes, bolt in April, and beginflowering during May and June. Flowering willcontinue until frost or until soil moisture is no longer

available (Thill et al. 1999).


Seed production: From 2 to 23 seeds/plant, dependingon growing conditions.

Seed bank: Most seeds germinate in the first autumnfollowing an after-ripening period. Seeds can survive inthe soil up to 32 months.

Dispersal: Seed can disperse short distances by windand water, on the fur of rodents and other wildlife, aswell as on hooves of cattle.

Hybridization: The 2 varieties of common crupina canhybridize.

Thill, D. C., C. T. Roche, and D. L. Zamora. 1999.Common crupina. In R. L. Sheley and J. K. Petroff,eds. Biology and Management of Noxious RangelandWeeds. Corvallis: Oregon State University Press.

Biocontrol: None.

Mechanical: Hand-pulling or hoeing can be effectivefor small infestations. Plants should be controlledbefore they set seed, and follow-up treatments may benecessary.

Fire: Prescribed burning has reduced seedlingpopulations, but long-term effects are unknown.

Herbicides: Clopyralid, 2,4-D, dicamba, and picloramhave been effective. Consult the most recent edition ofBC Ministry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Seed competitive grasses ondisturbed sites to prevent invasion and promote control.Managing grazing animals to minimize disturbance andmaintain perennial plant communities can effectively

control this weed, provided the grasses are welladapted to the site. Clean livestock before moving themto a new area.


41


Management ________________________________________

References __________________________________________

Integrated Management Summary

Successful management of common crupinarequires site-specific integration of severalcontrol methods (Thill et al. 1999). Preventiveactions and prompt control of new outbreakswill stop new infestations, while combinationsof herbicides, prescribed burns, reseeding, andgrazing management will control existingcrupina populations.


Growth form:Annual, winterannual, or sometimes

biennial forb.

Flower: Flower heads arenumerous and have yellow diskflowers but no ray flowers. The floralbracts (phyllaries) are black-tipped.

Seeds/Fruit: Seeds have white hairs(pappus) that promote wind dispersal.

Leaves: Leaves are alternate, coarselyand irregularly toothed, or pinnatelyparted.

Stems: Mature plants have erect,branched stems 0.25–1.4 m tall.

Roots: Small taproot withsecondary fibrous root system.

Seedling: Seed leaves(cotyledons) and young leaves arepurple below.

Similar Species

Exotics: Woodland groundsel(Senecio sylvaticus) is frequent incoastal and southwestern BC.

Natives: Thirty-two native andintroduced species of Senecio occurin the province (Douglas et al. 1998).

Agricultural: A problematic weed in cultivated crops,gardens, and nurseries. Poisonous to cattle and horses.


Human: Contains pyrrolizidine alkaloids, which cancause irreversible liver damage and possibly death inhumans.

COMMON GROUNDSEL

Senecio vulgaris L.Family: Asteraceae (Sunflower).


Other Common Names: Old-man-in-the-spring.



42

Impacts ____________________________________________


General requirements: Grows mainly in cultivatedsoil but may be found in pastures or along roadsidesand disturbed areas. It is best adapted to wetenvironments and nutrient-rich soils.

Distribution: Common in west-central andsouthwestern BC, but rare elsewhere in the province(Douglas et al. 1998). Present in all agriculturalreporting regions but not considered a major concern inany region. It is widely distributed throughout the US.


Life cycle: Seeds germinate in late autumn or early

spring. Seedlings appear as tiny rosettes with sharplynotched leaves that are purple on the underside.Common groundsel flowers from April throughOctober. Seeds may mature in opened flowers evenafter the plants have been killed.




Dispersal: Seeds are easily dispersed by wind.


Biocontrol: None.

Mechanical: In croplands, tillage in autumn and earlyspring will kill common groundsel seedlings. Smallinfestations can be pulled and larger infestations can becut or mowed.


Herbicides: Many infestations have developedresistance to triazine herbicides. Consult the mostrecent edition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Common groundsel has arelatively small root system and is easy to hand-pull.Prevent establishment of new infestations by

minimizing disturbance and seed dispersal, eliminatingseed production, and maintaining vigorous perennialplant communities.


Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Common groundsel. Weeds of the West. WesternSociety of Weed Science, in cooperation with theWestern United States Land Grant UniversitiesCooperative Extension Services, Newark, CA.


43

References __________________________________________

Management ________________________________________

Integrated Management SummaryEnsure that grazing management maintainsvigorous perennial plant communities. Cut,hand-pull, and apply herbicides immediately ifthis plant invades. Seed disturbed area toprovide adequate ground cover to preventinvasion.


Flower: Yellow flowers are numerous inflat-topped,

dense clusters at thetops of the plants.Button-like flowerheads lack ray flowers.

Seeds/Fruit: Seeds(achenes) are yellowishbrown with short, 5-toothed crowns.

Leaves: Alternate,deeply divided intonumerous narrow, individualleaflets.

Stems: Mature plants are 0.4–1.5 m tall. The erectstems are often purplish red and dotted with glands.

Roots: Rhizomatous.


Similar Species



Agricultural: Considered an undesirable forage andmay be toxic to livestock.

Ecological: No confirmed information but maydisplace native species.

Human: Can be toxic if large quantities are consumed.

COMMON TANSY

Tanacetum vulgare L.Family: Asteraceae (Sunflower).


Other Common Names: Garden tansy.

Legal Status: Regional Noxious: Bulkley-Nechako, CentralKootenay, Columbia-Shuswap, East Kootenay, North Okanagan.


44

Impacts ____________________________________________


Habitat and Ecology __________________________________General requirements: Common tansy grows at low-to mid-elevations along roadsides, on stream banks,and in disturbed habitats and pastures. It grows best infull sun and in fertile, well-drained soil.

Distribution: This weed is common in BC south of 55o

N (Douglas et al. 1998) and is present in allagricultural reporting regions of the province. It isconsidered a major concern in the Kootenay,Okanagan, and Omineca regions.

Historical: Introduced from Europe as an ornamentaland medicinal herb (Whitson et al. 1996). It has been

used for centuries for treating various ailments and asan insect repellent.

Life cycle: Flowering typically occurs from July toSeptember.






Biocontrol: None.

Mechanical: Common tansy can be mowed beforeflowering and seed-set to eliminate seed production.This method may have to be repeated to eliminateregrowth from rootstocks.


Herbicides: Picloram, dicamba, and glyphosate can beused to manage this plant. The best time for treatmentis between the early flower (bud) to bloom stage (DowAgroSciences 1998). Consult the most recent edition ofBC Ministry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Prevent the establishment of newinfestations by minimizing disturbance and seeddispersal, eliminating seed production, and maintaininghealthy native communities.


Dow AgroSciences. 1998. Common tansy—biennials/perennials. Dow AgroSciences. The Ranch,Pasture Improvement.http://www.dowagro.com/theranch/weeds.asp[5 Mar 99].

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Common tansy. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.


45

Management ________________________________________

References __________________________________________

Integrated Management SummaryMechanical methods, such as mowing or hand-cutting, are most effective in combination withother management measures because this plantis rhizomatous. Plants can regrow from severedroots, and cut stems may still produce viableseed. Manage the spread of common tansy bypreventing seed production and dispersal,minimizing the spread of cut rootstocks, andestablishing vigorous stands of perennialplants.

General requirements: Tolerates dry to moderatelydry conditions and is adapted to well-drained, acidicsoils. Found in cultivated fields, abandoned fields, anddisturbed habitats.

Distribution: Most common in coastal areas of theprovince, but occurs in all agricultural reportingregions. It is found throughout the Pacific Northweststates and most of Canada.


Life cycle: Plants germinate in the spring; floweringbegins by June and continues through October (BCMinistry of Agriculture and Fisheries 1988).


Seed production: Each plant can produce as many as10,000 seeds (Royer and Dickinson 1999).

Growth form: Annualforb.

Flower: Whiteflowers are numerous, small(about 6 mm across), andborne in forked clusters at theend of the stems.

Seeds/Fruit: Capsules areegg-shaped, 1.2–2.2 cm long,and contain numerous seeds.The tiny seeds (1.0–1.5 mm)are blackish with tiny whitishwarts. They are circular, exceptfor a notch on one side and anarrow, winged margin.

Leaves: The slender, fleshyleaves are attached to each stemnode in whorls of 6–10. Eachneedle-like leaf is about 1 mm thick,

20–50 mm long, rounded on the upper surface, andgrooved on the lower.

Stems: Several, branched, yellowish green, somewhatsticky, prostrate to erect, and 10–60 cm tall.

Roots: Small taproot.

Seedling: Seedlings have a few needle-like leaves witha blunt tip arising from the centre of the sprout.

Similar Species

Exotics: The Pink family contains many weedyspecies, but none have the whorled, needle-like leavesof corn spurry.

Natives: The sand spurries (Spergulariasp.) resemble corn spurry, but theyhave opposite leaves and their seedshave broad wings on the margins(Frankton and Mulligan 1970).

Agricultural: A problem of grain fields and othercropland. The weed is an alternate host for some viraldiseases.

Ecological: Grows in fields and disturbed habitats,often on sandy, gravelly, or acidic soils.


CORN SPURRY

Spergula arvensis L.Family: Caryophyllaceae (Pink).


Other Common Names: Sandweed, pickpurse.



46

Impacts ____________________________________________



Seed bank: Seeds may remain viable in the soil aslong as 10 years.

Dispersal: Contaminated soils and crop plant materials

carry seeds. Seeds can also be dispersed by vehicles,humans, and animals.


BC Ministry of Agriculture and Fisheries. 1988. Cornspurry (Spergula arvensis). Weed Series Fact Sheet—Agdex 640.

Douglas, G. W., G. B. Straley, D. Meidinger, and J.Pojar, eds. 1998. Illustrated Flora of British Columbia.Vol. 2: Dicotyledons (Balsaminaceae throughCuscutaceae). Province of British Columbia.

Frankton, C., and G. Mulligan. 1970. Weeds ofCanada. Publication 948. Ottawa: Canada Departmentof Agriculture.


Biocontrol: None.

Mechanical: Repeated, shallow tillage can inducegermination and destroy emerging seedlings. Weedsshould be tilled before they set seed.


Herbicides: Corn spurry is resistant to 2,4-D andMCPA. Dicamba and dicamba mixes are used onpastures and rangelands when the weeds are activelygrowing. Consult the most recent edition of BCMinistry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Small infestations can be hand-pulled or hoed. Remove plants before seed-set.


47

Integrated Management SummaryUse clean, high-quality seed. Maintaincultivated crops and forages in a competitivecondition. Prevent seed production throughtillage or herbicide use.

Management ________________________________________

References __________________________________________


Flower: Flowers are borne on long stalks(up to 15 cm long) at branches and at the

end of the stems. The typical buttercup flowers arebright yellow with 5 or more petals. Each petal is 6–18mm long and 5–12 mm wide. The sepals are greenishand soon drop off.

Seeds/Fruit: The seeds are clustered in a globe- to egg-shaped head 5–10 mm long and 5–8 mm wide (Douglaset al. 1999). The seeds are egg-shaped to circular,strongly flattened, about 3 mmlong, and tipped with a short,curved beak.

Leaves: Basalleaves areborne on stalksup to 40 cmlong. Each leafhas 3 parts,with eachleaflet eitherlobed or

divided again. Stem leaves are alternate. The lowerstem leaves are similar to the basal leaves with longstalks, but the leaves become smaller, simpler, andstalkless moving up the stem.

Stems: The slightly hairy stems are usually hollow andcan be up to 1 m long. Some stems are erect, but eachplant usually has one or more stems (stolons) that creepalong the ground and root freely at the nodes.

Roots: Slender, shallow, fibrous roots.


Similar Species

Exotics: Creeping buttercup is the only introducedbuttercup with a creeping habit. Tall buttercup(Ranunculus acris) is sometimes confused withcreeping buttercup, and both grow in the same habitats.Tall buttercup has a more upright growth habit anddeeply incised leaves.

Natives: Macoun’s buttercup (Ranunculus macounii)resembles creeping buttercup and shares similarhabitats. It has hairy stems and smaller flowers (4–6mm long and 3–5 mm wide).

Agricultural: A common weed of grain and foragecrops that depletes the soil of potassium and othernutrients, causing deficiencies in associated crops(Lovett-Doust et al. 1990). This plant is mostproblematic in BC on poorly drained permanentpastures, where it reduces carrying capacity. Manybuttercups contain an acrid juice that causes oral andgastrointestinal inflammations in livestock (Franktonand Mulligan 1970).

Ecological: Colonizes disturbed areas. It is usuallyfound in heavy, wet clay soils but can also survive insand or gravel when moisture is adequate (Lovett-Doust et al. 1990). It often grows by streams, swamps,and ponds, and in seepage areas. It can dominatedisturbed riparian areas, forest openings, and alongpaths.

Human: Occasionally used as a ground cover inornamental plantings.

CREEPING BUTTERCUP

Ranunculus repens L.Family: Ranunculaceae (Buttercup).





48

Impacts ____________________________________________


General requirements: Adapted to a wide range ofclimatic zones, except during prolonged droughts. Itgrows along stream banks, ditches, roadsides, lawns,meadows, pastures, and cultivated crops. It commonlyoccurs in poorly drained disturbed habitats.

Distribution: Present in all of the province’sagricultural reporting regions except for the Ominecaand Peace River districts. It occurs across Canada andthe US, where it is distributed in a band extendingmainly between 30o and 50o N (Lovett-Doust et al.1990).


Life cycle: Plants overwinter as leafy rosettes with acrown and roots in mild climates such as those of BC,or as roots with a crown where winters are more severe(Lovett-Doust et al. 1990). In spring, lateral stolons areproduced that spread, root at the nodes, and producesmall clone plants. This process is repeated untilautumn, when the stolon internodes wither and the new

plants become independent. Some plants flower and setseed during the growing season. Seeds overwinter andgerminate the following spring.

Mode of reproduction: Primarily by rooting alongstolons but also from seed.

Seed production: There are less than 100 seeds/plant,and only about 25% of flowering plants set seed.

Seed bank: Seed densities can be up to 12,000seeds/m2 in pastures (Lovett-Doust et al. 1990). Newseeds appear to be dormant and germinate sporadicallyover the year. Buried seeds can remain viable for up to5 years.

Dispersal: Seeds are dispersed by wind, birds, rodents,and livestock. Vehicles and human activities alsospread the seeds. Plants fragment easily, and anyhuman activities that disturb soils could spread theweed.

Hybridization: Little evidence of hybridization.

Douglas, G. W., D. Meidinger, and J. Pojar, eds. 1999.Illustrated Flora of British Columbia. Vol. 4:Gymnosperms and Dicotyledons (Orobanchaceaethrough Rubiaceae). Province of British Columbia.


Lovett-Doust, J., L. Lovett-Doust, and A. T. Groth.1990. The biology of Canadian weeds. 95. Ranunculusrepens. Canadian Journal of Plant Science 70:1123–1141.


Biocontrol: None.

Mechanical: Repeated tillage over several years mayreduce root reserves and control the plant on cropland,but root fragments easily regenerate (Muenscher 1955).

Fire: Not effective.

Herbicides: Glyphosate, MCPA, and 2,4-D areeffective with spring and autumn applications whilecrops are dormant. Mecoprop provides effective controlin turf. Consult the most recent edition of BC Ministryof Agriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Seed disturbed areas to perennialgrasses and forbs. Manage grazing animals to maintaina perennial plant community that can providecompetition. Improve drainage.


49


Management ________________________________________

References __________________________________________

Integrated Management SummaryUse tillage, hand-pulling, and herbicides, asappropriate. Prevent new infestations byseeding disturbed areas, managing grazinganimals to maintain perennial plantcommunities, and seeding disturbed areas.


Flower: Numerous smallflowers are clustered at the end

of the stem in a large, dense panicle up to60 cm long. Flower clusters are greenishred initially, then mature to pinkish, andfinally, to brown. Flower stalks arejointed. Petals are absent; instead thereare an outer whorl of 3 green sepals andan inner whorl of 3 red sepals (Royerand Dickinson 1999), each with a grain-like swelling.

Seeds/Fruit: A 3-sided achene isenclosed by the inner sepals. Seedsare reddish brown, about 10 mmlong, shiny, and 3-sided (Franktonand Mulligan 1970).

Leaves: Dark green basal leaves,10–30 cm on long, pimply, finely hairystalks. Stem leaves are alternate andbecome smaller with shorter stalksmoving up the stem. A papery sheathsurrounds the stem at the leaf joint. Leaveshave pronounced wavy and crisped (curled) margins.

Stems: Reddish stems up to 1.6 mtall are unbranched below theinflorescence and are usuallysolitary (Douglas et al. 1999).

Roots: Stout, fleshy taproot with ayellow centre that can extend 1.5 minto the soil.

Seedling: Cotyledons are oblong andpale green. Lance-shaped leaves haveprominent veins on the underside and havea papery sheath at the base (Royer andDickinson 1999).

Similar Species

Exotics: There are several other dock species, but mostare not tall, unbranched plants with crisped and wavyleaf margins. Broadleaved dock (Rumex obtusifolius)and patience dock (Rumex patientia) most closelyresemble curled dock, but their leaves are morerounded—not as wavy or as crisped. Broadleaved dockhas larger leaves that are rounded or heart-shaped atthe base (Cranston et al. 2000).

Natives: The native docks (Rumex sp.) do not resemblecurled dock.

Agricultural: Can be a problem in cultivated cropland,pastures, and hayfields. Seeds and vegetation are toxicto poultry (Royer and Dickinson 1999) and causedermatitis and gastric problems when large amountsare eaten by cattle (Northern Prairie Wildlife Center.Undated). It is an alternate host to many crop diseases.

Ecological: Open, disturbed areas are often invaded.This weed is especially common in riparian areas,including wet meadows, pond edges, and irrigationditches, but its impacts on native plant communitieshave not been documented.


CURLED DOCK

Rumex crispus L.Family: Polygonaceae (Buckwheat).


Other Common Names: Curly dock, sour dock, yellow dock.



50

Impacts ____________________________________________


General requirements: Adapted to moist to wet soils inopen sites and can tolerate poor drainage. In BC, itgrows in cultivated crops, pastures, fencerows, andriparian areas, especially those that have been disturbed.

Distribution: Found in every agricultural reportingregion of BC. Curled dock occurs across Canada andthe US.


Life cycle: A rosette measuring 10–30 cm long isproduced in the first year. Plants produce tall, floweringstalks beginning in the second year that flower fromJune to September, depending on geographic location.

Mode of reproduction: Vegetatively from rootfragments and by seed.

Seed production: About 30,000–60,000 seeds/plant(Northern Prairie Wildlife Research Center. Undated).

Seed bank: Nearly 90% of seeds will germinate withadequate light, but seeds that are buried more than 3cm in the soil will remain dormant and are extremelylong lived (Northern Prairie Wildlife Research Center.Undated). About half are viable after 50 years andsome survive to 80 years (Royer and Dickinson 1999).

Dispersal: Primarily by wind or water. Rough seedpods stick to fur and feathers of animals and seeds canpass through cattle or wildlife. Cultivation or other soildisturbances disperse root fragments.

Hybridization: Broad-leaved dock (Rumexobtusifolius) and curled dock often hybridize.


Douglas, G. W., D. Meidinger, and J. Pojar, eds. 1999.Illustrated Flora of British Columbia. Vol. 4.Gymnosperms and Dicotyledons (Orobanchaceaethrough Rubiaceae). Province of British Columbia.


Royer, F., and R. Dickinson. 1999. Weeds of Canadaand the Northern United States. Edmonton:University of Alberta Press.

Rutledge, C. R., and T. McLendon. Undated.An assessment of exotic plant species ofRocky Mountain National Park. Departmentof Rangeland Ecosystem Science, ColoradoState University. Northern Prairie WildlifeResearch Center Home Page.http://www.npwrc.usgs.gov/resource/othrdata/Explant/explant.htm [15 Dec 98].

Biocontrol: None.

Mechanical: Cultivation induces seedling emergencebut requires follow-up treatment for control.Cultivation may spread established plants with well-developed root systems. Mowing before plants flowercan prevent seed production.

Fire: No information is available, but fire would notlikely affect the deep taproot.

Herbicides: Spring applications of MCPA, dicamba,and 2,4-D amine, when seedlings are at the 2–4 leafstage, have been effective. Glyphosate applied in fullleaf stage will control dock prior to ploughing. Newseedlings can be suppressed with MCPA/MCPB or 2,4-DB. Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: New infestations can becontrolled by hand-pulling or digging up plants. Seeddisturbed areas to perennial grasses, and managelivestock to maintain perennial plant communities.


51


Management ________________________________________

References __________________________________________

Integrated Management SummaryCurled dock is shade intolerant and a poorcompetitor in dense stands of other plantspecies. Maintain vigorous perennial stands onforage crops and native plant communities,especially in riparian areas where control withherbicides may not be possible. Minimize soildisturbance in riparian areas since exposure tolight stimulates germination.



Flower: Flowers areborne in loose,

elongate, terminal racemes.Flowers are bright yellow andresemble snapdragons.

Seeds/Fruit: Fruits areegg-shaped to nearly roundcapsules. Seeds are sharplyangular and slightly winged.

Leaves: Leaves are broad, ovateto ovate-lanceolate, and arealternate, generally clasping butcrowded.

Stems: Mature plants are 0.6–1.2 m tall. A singletoadflax plant contains 1–25 vertical floral stems.

Roots: The taproot may penetrate 1 m into the soil.Horizontal roots may grow to beseveral meters long and can developadventitious buds that may formindependent plants.


Similar Species

Exotics: Yellow toadflax (Linaria vulgaris) is similarin appearance but has more linear pointed leaves and isgenerally smaller.


Agricultural: Low-till cultivation practices havecontributed to the resurgence of toadflax populationson agricultural lands (McClay 1992). Dalmatiantoadflax contains a glucoside, a quinoline alkaloid, andpeganine, which make it toxic to livestock. However, itis generally considered unpalatable to livestock (Reeset al. 1996). Reports of livestock poisonings are rare.

Ecological: Dalmatian toadflax is a persistent,aggressive invader and capable of forming dense

populations through creeping root systems. Populationscan compete with native grasses and other forbs,altering the species composition of naturalcommunities. Infestations also can occur in smallopenings on excellent-condition rangeland (Lajeunesse1999). Toadflax can also reduce forage production forlivestock and other ungulates (Robocker 1974).


DALMATIAN TOADFLAX

Linaria genistifolia spp. dalmatica (L.)Marie and Petitmengin Family: Scrophulariaceae (Figwort).

Other Scientific Names: Linaria dalmatica.

Other Common Names: Broad-leaved toadflax, wild snapdragon.



52

Impacts ____________________________________________


General requirements: In BC, grows at low- to mid-elevations in the Interior along roadsides and in disturbedareas, gardens, cultivated fields, grassland, andtransitional forest-grassland (Powell et al. 1994). It canadapt to a wide range of environmental conditions and istolerant of low temperatures and coarse, textured soils.

Distribution: Occurs widely throughout Canada andthe US, but the heaviest infestations are found in BC,

Alberta, and the northwestern US (Lajeunesse 1999).It occurs throughout the Okanagan, Similkameen,Thompson, East Kootenay, Cariboo, Skeena, andBoundary areas (Powell et al. 1994). It is regarded as amajor concern in all of the province’s agriculturalreporting regions except the Mainland.

Historical: Introduced from Europe, likely as anornamental.

Life cycle: Plants emerge mid-April, depending ongeographic location. During the first year the plantforms a rosette and develops a deep root system.Prostrate stems emerge in autumn and produce ovateleaves. These stems are tolerant to freezing anddevelop into floral stems the following year (Robocker1974). Floral stems develop after winter dormancy andemerge about the same time as new seedlings in mid-April. A single plant can produce 1–25 floral stems.Flowering occurs from May to August and seedsmature from July to September. Dalmatian toadflaxalso reproduces vegetatively from root buds and

possibly from root fragments (Zimmerman 1996). Themain taproot may penetrate 0.9–1.2 m into the soil, andlateral roots can extend up to 3.7 m.


Seed production: A mature plant can produce up to500,000 seeds annually (Morishita 1991).

Seed bank: Seeds may remain viable up to 10 years.

Dispersal: By wind and animals. Deer, elk, and birdseat seeds and seed heads.


Biocontrol: Five agents occur in BC: Brachypteroluspulicarius (beetle), Calophasia lunula (moth),Eteobalea intermediella (moth), Gymnaetron antirrhini(weevil), and Mecinus janthinus (beetle). Mecinusjanthinus has established well in several areas of theprovince and reduction in toadflax populations havebeen recorded (Dr. R. DeClerk-Floate: Personalcommunication to Dr. Brian M. Wikeem).

Mechanical: Cutting plants reduces topgrowth seedreproduction but will not kill the plant. Hand-pullingtoadflax before seed-set each year can be an effectivemanagement method for new and small populations,especially if a seed bank has not developed. On a localbasis, sheep grazing can suppress infestations andreduce seed production (Lajeunesse 1999), but grazingshould be applied before the plants set seed.


Herbicides: Autumn applications of picloram andpicloram mixed with 2,4-D have provided managementon some sites. In a US study, diclorprop was alsoeffective at management. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Intensive disking can be an

effective management method on cropland under somecircumstances. This method requires at least 2 yearswith 8–10 cultivations in the first year, and 4–5cultivations in the second year (Morishita 1991).Follow-up seeding with appropriate perennial species isalso required to provide competition with the weed.Hand-pulling can be effective for small infestations ina new area. Pull plants before seed-set to eliminatedevelopment of a seed bank.


53

Integrated Management SummaryIntegrated management should focus onimpeding vegetative spread and reducing seedproduction (Lajeunesse 1999). Successfulcontrol can be obtained by pulling or killingthe plants with herbicide before toadflax seedproduction begins (Carpenter and Murray1998). Since the plant also spreads vegetativelyand viable seeds remain in the soil for up to 10years, these treatments must be repeated forseveral years to eradicate the stand locally.Seed disturbed areas to perennial grasses andforbs to provide ground cover and competition.

Management ________________________________________

References __________________________________________

Carpenter, A. T., and T. A. Murray. 1998. Elementstewardship abstract for Linaria dalmatica. The NatureConservancy, Wildland Weeds Management andResearch Program.http://tncweeds.ucdavis.edu/esadocs.html

Lajeunesse, S. 1999. Dalmatian and yellow toadflax. InR. L. Sheley and J. K. Petroff, eds. Biology andManagement of Noxious Rangeland Weeds. Corvallis:Oregon State University Press.


54

McClay, A. S. 1992. Effects of Brachypteroluspulicarius (L.) (Coleoptera: Nitidulidae) on floweringand seed production of common toadflax. TheCanadian Entomologist 124: 631–636.

Morishita, D. W. 1991. Dalmatian toadflax, yellowtoadflax, black henbane, and tansy mustard:Importance, distribution, and control. In L. F. James, J.O. Evans, M. H. Ralphs, and R. D. Child, eds. NoxiousRange Weeds. Boulder, CO: Westview Press.

Powell, G. W., A. Sturko, B. M. Wikeem, and P. Harris.1994. Field Guide to the Biological Control of Weedsin British Columbia. Land Management Handbook No.27. BC Ministry of Forests.

Rees, N. E., P. C. Quimby, Jr., G. L. Piper, E. M.Coombs, C. E. Turner, N. R. Spencer, and L. V.Knutson (eds). 1996. Biological Control of Weeds inthe West. Western Society of Weed Science incooperation with USDA Agricultural Research Service,Montana Department of Agriculture, and MontanaState University.

Robocker, W. C. 1974. Life history, ecology, andcontrol of Dalmatian toadflax. Technical Bulletin No.79. Pullman: Washington Agricultural ExperimentStation.

Zimmerman, J. A. C. 1996. Ecology and distribution ofLinaria vulgaris (L.) Miller, Scrophulariaceae. USGSColorado Plateau Field Station, Southwest Exotic PlantMapping Project.http://www.usgs.nau.edu/swemp/Info_pages/plants/Linaria/linariatitle.html [14 Jan 98].


55


Growth form: Biennialor short-livedperennial forb.

Flower: Flower heads arebroadly urn-shaped, 1.5–2.0 cmtall, solitary or in clusters of 2–3at the ends of the branches. Floralbracts are yellowish with a brownishmargin, sometimes spotted, fringed onthe sides, and terminating in a slenderbristle or spine. The heads contain 2types of flowers: ray flowers aroundthe edges surrounding tubular diskflowers. The ray flowers are white,rose-purple, or lavender.

Seeds/Fruit: Seeds are light brownto black.

Leaves: Basal leaves are stalked and divided intonarrow, hairy segments. Stem leaves are smaller,alternate, less divided, and stalkless, andbecome bract-like near the flower clusters.

Stems: Stems are upright, 10–60 cm tall,highly branched, angled, with short, stiffhairs on the angles.

Roots: Taproot.

Seedling: Seedlings have finely dividedleaves that are covered with short hairs.

Similar Species

Exotics: Diffuse knapweed may be distinguished fromother knapweeds by the terminal spine on the floralbract.

Natives: None.

Agricultural: Reduces the productivity of rangelandby displacing desirable forage species for livestock andwildlife.

Ecological: A pioneer species that can quickly invadedisturbed plant communities, reduce biological

diversity, and increase soil erosion (Watson andRenney 1974; Sheley et al. 1997).


DIFFUSE KNAPWEED

Centaurea diffusa Lam.Family: Asteraceae (Sunflower).


Other Common Names: Spreading knapweed, tumble knapweed.



56

Impacts ____________________________________________


General requirements: Diffuse knapweed is found ongrasslands, shrub lands, and dry open forests at low- tomid-elevations in BC. It occurs in pastures, alongroadsides, and on disturbed areas in both rural andurban environments. Diffuse knapweed is not commonon cultivated lands or irrigated pasture because itcannot tolerate cultivation or excessive moisture(Watson and Renney 1974).

Distribution: Diffuse knapweed is distributedthroughout southern BC east of the Coast-Cascade

mountains. It is considered a major concern in theKootenay, Okanagan, Thompson, Cariboo, Omineca,and Peace River agricultural reporting regions. Pocketsalso occur in the Chilcotin (Powell et al. 1994). Theplant is widely spread throughout the northwestern US.


Life cycle: Diffuse knapweed is usually regarded as abiennial, although some plants may remain as rosettesfor several years, depending on environmentalconditions (Thompson and Stout 1991). Flower buds

are usually formed in early June, flowering occurs inJuly, and seeds are formed by mid-August (Watson andRenney 1974).


Seed production: A single diffuse knapweed plant canproduce up to 18,000 seeds (Harris and Cranston1979), and a stand of diffuse knapweed can produce upto 40,000 seeds/m2 (Watson and Renney 1974).

Seed bank: Seeds may remain dormant in the seedbank for many years.

Dispersal: Seeds are distributed around the parentplant when plants sway in the wind, but mature plantsoften break at the stem and become tumbleweeds,allowing seeds to disperse over great distances (Watsonand Renney 1974; Zimmerman 1997). Livestock,wildlife, and humans also readily disperse the plant.


Biocontrol: Ten biological control agents have beenreleased on diffuse knapweed in the province: Agapetazoegana (moth), Chaetorellia acrolophi (fly), Larinusminutus (weevil), Larinus obtusus (weevil), Pelochristamedullana (moth), Pterolonche inspersa (moth),Puccinia jaceae (stem and leaf rust), Sphenopterajugoslavica (beetle), Urophora affinis (fly), andUrophora quadrifasciata (fly) (Powell et al. 1994). Inaddition, Cyphocleonus achates (weevil) hassuccessfully moved onto diffuse knapweed in somehabitats.

Mechanical: Cutting or mowing before seed-set can beeffective to reduce seed production, but it will noteliminate large infestations. Cut plants and rosettesmay survive and re-bolt. Ideally, mowings should befollowed by an autumn herbicide treatment (Sebastianand Beck 1999). Hand-pulling can be effective onsmall infestations, but it often needs to be repeated,depending on the size of the initial weed population.

Fire: The direct effects of fire to control diffuseknapweed have been conflicting. One study reportedthat neither spring nor autumn burning reducedknapweed populations on 2 grassland sites near Vernon(Nicholson 1992). In another study, Zimmerman (1997)reported that fire effectively controlled diffuseknapweed, and a vigorous stand of grasses occupiedthe burned sites. Under some circumstances, fire can beused to remove standing dead material, which mayincrease the efficacy of herbicides applied after theburn (Roche and Roche 1999).

Herbicides: Several herbicides are effective to controldiffuse knapweed. Picloram is the most widely

recommended (Harris and Cranston 1979). Otherherbicides, such as clopyralid, dicamba, 2,4-D, andglyphosate, are also effective (Beck 1997; Youtie 1997;Watson and Renney 1974). To maximize effectiveness,herbicides should be applied before plants set seed, orto rosettes in the autumn. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides readthe label for full use and precautionary instructions.

Cultural/Preventive: Prevent establishment bymanaging to minimize disturbance. Clean machinery,vehicles, and equipment. Manage grazing or other landuse to maintain vigorous native communities.


57

Integrated Management SummaryThe most effective management method fordiffuse knapweed is to prevent establishment.Small infestations should be dealt withimmediately by hand-pulling the plants,herbicide application, or both. Seed disturbedsites immediately to prevent further infestation.Follow-up is essential to ensure that the initialtreatment was effective. On sites too large forthese methods to be effective, biocontrolshould be considered.

Management ________________________________________


58

Beck, K. G. 1997. Diffuse and spotted knapweed.Colorado State University Cooperative ExtensionNatural Resource Series, No. 3. 110.http://www.ext.colostate.edu/pubs/natres.html [24 Jan00].

Beck, K. G., J. R. Sebastian, and L. R. Rittenhouse.1998. The influence of cattle grazing on diffuseknapweed populations in Colorado. Proceedings of theWestern Society of Weed Science. 51: 63.

Fletcher, R. A., and A. J. Renney. 1963. A growthinhibitor found in Centaurea sp. Canadian Journal ofPlant Science 43: 475–481.

Harris, P., and R. Cranston. 1979. An economicevaluation of control methods for diffuse and spottedknapweed in western Canada. Canadian Journal ofPlant Science 59: 375–382.

Nicholson, R. A. 1992. Impact of prescribed burningon diffuse knapweed (Centaurea diffusa) infestationsand floral diversity in Kalamalka Lake Provincial Park.M.Sc. thesis, University of British Columbia.

Niefoff, J. E-mail message-broadcast. Sent 9-12-97,9:29 a.m.


Roche, B. E., and C. T. Roche. 1999. Diffuseknapweed. In R. L. Sheley and J. K. Petroff, eds.Biology and Management of Noxious RangelandWeeds. Corvallis: Oregon State University Press.

Schirman, R. 1981. Seed production and springseedling establishment of diffuse and spotted knapweedon Colorado rangeland. Journal of RangelandManagement 34: 45–47.

Sebastian, J. R., and K. G. Beck. 1999. The influenceof various control methods on diffuse knapweed onColorado rangeland. Proceedings of the WesternSociety of Weed Science 52: 41.

Sheley, R. L., B. E. Olson, and L. L. Larson. 1997.Effect of weed seed rate and grass defoliation level ondiffuse knapweed. Journal of Rangeland Management50: 39–43.

Thompson, D. J., and D. G. Stout. 1991. Duration ofthe juvenile period in diffuse knapweed (Centaureadiffusa). Canadian Journal of Botany 69: 368–371.

Watson, A. K., and A. J. Renny. 1974. The biology ofCanadian weeds. Centaurea diffusa and C. maculosa.Canadian Journal of Plant Science 54: 687–701.

Youtie, B. 1997. Weed control as the first step inprotecting and restoring native plant communities onnortheast Oregon natural areas. Conservation andManagement of Native Plants and Fungi. Corvallis:Native Plant Society of Oregon.

Youtie, B., and J. Soll. 1994. Non-chemical control ofdiffuse knapweed (Centaurea diffusa). KnapweedNewsletter 8 (3): 2–3. Pullman: Washington UniversityCooperative Extension.

Zimmerman, J. A. C. 1997. Ecology and distribution ofCentaurea diffusa Lam., Asteraceae. USGS ColoradoPlateau Field Station, Southwest Exotic Plant MappingProject.http://www.usgs.edu/swemp/Info_pages/plants/Centaurea_diffusa/diffusa.html [16 Feb 98].

References __________________________________________


59



Flower: Flowers are funnel shaped, up to2.5 cm across, white to pink, and borne

singly or in pairs on long stalks from the axils of theleaves with 2 tiny bracts.

Seeds/Fruit: Conical capsules contain ovoid to pear-shaped seeds. The dull, brownish grey seeds are 3-angled with 1 rounded and 2 flattened sides.

Leaves: Leaves are alternate, simple, glabrous to finelypubescent, more or less arrowhead-shaped.

Stems: Slender,twining stemsare prostrate, upto 3 m long,often climbingor formingdense mats.

Roots: The root system and rhizomes are extensive,whitish, cord-like, and fleshy. The primary root is ataproot from which lateral roots develop (Peterson1998).

Seedling: Seed leaves (cotyledons) are spatulate andbroad and indented at the tip.

Similar Species

Exotics: Black bindweed (Polygonum convolvulus) inthe knotweed family (Polygonaceae) is similar butinfrequent in southern BC and rare northward. Hedgebindweed (Convolvulus sepium) has larger leaves andflowers. This species is native to eastern NorthAmerica but has been introduced into the province(Douglas et al. 1998).


Agricultural: Can reduce crop yields and its twiningstems can interfere with harvesting and landscapeplantings. It also acts as an alternate host for some cropdiseases.

Ecological: Field bindweed can be a threat to nativeplant communities because of its broad range of

environmental tolerances (Peterson 1998). Detachedroots and rhizomes can produce large numbers of newshoots. The plant produces a large number of seeds thatremain viable in the soil for long periods.


FIELD BINDWEED

Convolvulus arvensis L.Family: Convolvulaceae (Morning-glory).


Other Common Names: Small-flowered morning glory, wildmorning glory, perennial morning glory, creeping jenny.



60

Impacts ____________________________________________


General requirements: Field bindweed grows incoastal and low- to mid-elevation regions of BC’sInterior, where it is found on cultivated lands,roadsides, and disturbed habitats, especially ondisturbed ground. Field bindweed cannot tolerate shadeand uses its viney stems to move into sunlight.Therefore, it is unlikely that field bindweed persists inlater stages of community succession (FEIS 1996).

Field bindweed is commonly found on more basic(rather than acidic) soil types and those of heaviertexture. It can persist in dry to moderately moist soilsand is capable of surviving drought (Rutledge andMcLendon. Undated).

Distribution: Field bindweed is common in southernBC, but rarely occurs as far northward as DawsonCreek (Douglas et al. 1998). It is present in the

Kootenay, Okanagan, Thompson, Mainland, andVancouver Island agricultural reporting regions, but itis not considered a major concern anywhere. It is foundthroughout most of Canada and the US.

Historical: Introduced from Europe as early as the1730s (Peterson 1998).

Life cycle: The leaves vary greatly in size and shapewith environmental factors, such as light intensity andsoil moisture, and with damage due to frequentcultivation. Flowers appear from June to Septemberand occasionally until the first autumn frost (Rutledgeand McLendon. Undated). Seeds mature within 2weeks of pollination. Germination occurs in theautumn or spring, over a wide range of temperatures(FEIS 1996). Field bindweed overwinters by means ofits roots and rhizomes. Shoots are killed back to thecrown by freezing temperatures, but hardened roots canwithstand temperatures as low as –6o C (Peterson

1998). Most lateral roots die back each year, but somepersist for several years, spreading horizontally(Peterson 1998). Buds arise on the lateral roots anddevelop into rhizomes that can establish as new crownswhen they reach the surface (Peterson 1998).


Seeds production: The number of seeds produced perplant ranges from 25 to 300, and seed production isvariable and depends on environmental conditions.

Seed bank: Seeds can remain viable in the soil forover 20 years (Peterson 1998).

Dispersal: Seeds have a hard, impermeable coat. Theygenerally fall near the parent plant, but can bedispersed by water, as a contaminant in crop seeds, andby mammals and birds after ingestion.


Douglas, G. W., D. Meidinger, and J. Pojar, eds. 1998.Illustrated Flora of British Columbia. Vol. 2:Dicotyledons (Balsaminaceae through Cuscutaceae).Province of British Columbia.


Peterson, D. L. 1998. Element stewardship abstract forConvolvulus arvensis, field bindweed. The NatureConservancy, Wildland Weeds Management andResearch Program.http://tncweeds.ucdavis.edu/esadocs/convarve.html [8Nov 98].

Rees, N. E., P. C. Quimby, Jr., G. L. Piper, E. M.Coombs, C. E. Turner, N. R. Spencer, and L. V.Knutson (eds). 1996. Biological Management of Weeds

Biocontrol: None in BC. Aceria mahlerbae (gall mite)and Tyta luctuosa (moth) are being studied in the US(Rees et al. 1996).

Mechanical: Cutting and mowing have little effect onplant populations unless plants are cut below the rootcrown at early stages of growth. Establishedpopulations have a large seed bank in the soil that canremain viable for over 20 years.

Fire: Fire is not recommended because of the plant’spotential for vegetative regrowth and a long-lived seedbank.

Herbicides: Foliar applications of glyphosate,picloram, dicamba, and 2,4-D have provided goodmanagement in the US during early flowering andwhen soil moisture is low (Peterson 1998). Chemicaltreatment often requires high rates and repeatedapplications. These can damage non-target species.Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Crop Production

Guides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Hand-pulling seedlings can beeffective for small, new infestations before plants setseed.


61

Integrated Management SummaryCutting, mowing, hand-pulling, and herbicidesall are possible methods to combine to managethis weed. Use both cultural and chemicalmethods as required when infestations aresmall. Seed disturbed areas with perennialgrasses and forbs to provide competitionagainst this weed.

Management ________________________________________

References __________________________________________


62

in the West. Western Society of Weed Science, incooperation with USDA Agricultural Research Service,Montana Department of Agriculture, and MontanaState University.


Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Field bindweed. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.


63


Growth form: Creepingperennial with both fertileand sterile stems.

Flower: Spore-bearing cones borne at thetop of fertile stems. Cones are rounded,1–4 cm long.

Seeds/Fruit: Spores.

Leaves: No true leaves, but whorlsof green, 4-angled, leaf-likebranches grow either outward ornearly erect from below thesheathed nodes on sterile stems.

Stems: Both fertile and sterilestems are jointed. Fertile stemsare light brown, unbranched andabout 30 cm tall. Sterile stems aregreen, 10–80 cm tall, and can beeither sprawling or erect. They

are hollow and grooved and have sheathed nodesand whorls of solid branches.

Roots: Extensive dark rhizomes with a felt-likesurface and small tubers (Frankton and Mulligan1970). Roots may extend 2 m deep (Royer andDickinson 1999).

Sporeling: Sporelings are the result offertilization of small male and female structurescalled prothalli that arise from the spores.Sporelings grow into the familiar horsetailplants (Cody and Wagner 1980).

Similar Species

Exotics: None.

Natives: Four horsetail species that are native to theprovince appear very similar to common horsetail.Swamp horsetail (Equisetum fluviatile) grows inriparian habitats and hybridizes with field horsetail.

Agricultural: Troublesome in pastures, hayfields,grain fields, orchards, nurseries, and small-fruit crops,especially on soils that are poorly drained or have ahigh water table (Cody and Wagner 1980). Plants arepoisonous to young horses and sheep, especially whendried in hay. Horsetail plugs harvesting equipment andcan delay drying of harvested grains and forages.

Ecological: Horsetail can form dense stands on

disturbed sites, such as roadsides and embankments. Itis common in undisturbed, wet habitats. It oftendominates riparian habitats, such as swamps andstream banks, and can be common in seepage areas offorests.

Human: Sometimes used medicinally. Also used asground cover to prevent soil erosion.

FIELD HORSETAIL

Equisetum arvense L.Family: Equisetaceae (Horsetail).


Other Common Names: Common horsetail, mare’s-tail, horsepipes.



64

Impacts ____________________________________________


General requirements: Tolerates a very wide range ofclimatic and soil conditions. Often found on wet,poorly drained soils, but it can grow in dry sandy orgravelly soil if there is a saturated sub-soil. In BC, fieldhorsetail is found in pastures, cultivated crops,orchards, landscape plantings, roadsides, embankments,

riparian sites, and shady forests.

Distribution: Occurs throughout BC, across Canada,and through much of the US. Present in all agriculturalreporting regions but not regarded as a major concernin any region.

Historical: Native to BC.

Life cycle: Fertile stems develop in early spring, thenspores are shed and fertile stems wither. Sterile stemsgrow as the fertile stems are fading and remain greenuntil autumn, then die. Rhizomes expand and send upnew, sterile shoots throughout the growing season.

Mode of reproduction: Spores, rhizomes, and roottubers. Rotting or fragmented rhizomes can producenew plants.

Spore production: Each cone produces about 100,000spores.

Seed bank: Spores are relatively short-lived. Theymust disperse to moist soil and germinate quickly inorder to survive.

Dispersal: Spring-like mechanisms inside the coneeject the spores for some distance. Tiny spores aredispersed by water. Fragmented rhizomes and tubersmay be transported by agricultural and road-buildingequipment (Cody and Wagner 1980).

Hybridization: Horsetails hybridize quite readily. InBC, field-swamp horsetail hybrids (Equisetum arvensex fluviatile) occur in riparian habitats where bothspecies grow (Douglas et al. 2000).

BC Ministry of Agriculture, Food and Fisheries. 1996.Crop Protection—Weed Control Factsheet. Horsetail(Equisetum).http://www.agf.gov.bc.ca/croplive/cropprot/hrsetail.htm

Cody, W. J., and V. Wagner. 1980. The biology ofCanadian weeds. 49. Equisetum arvense L. CanadianJournal of Plant Science 61: 123–133.

Douglas, G. W., D. Meidinger, and J. Pojar, eds. 2000.Illustrated Flora of British Columbia. Vol. 5.Dicotyledons (Salicaceae through Zygophyllaceae) andPteridophytes. Province of British Columbia.

Frankton, C., and G. A. Mulligan. 1970.Weeds of Canada. Publication 948.Ottawa: Canada. Department ofAgriculture.

Royer, F., and R. Dickinson. 1999.Weeds of Canada and the NorthernUnited States. Edmonton:University of Alberta Press.

Biocontrol: None.

Mechanical: Deep cultivation may give short-termcontrol, but cultivation may enhance the spread of thisplant by moving tubers and fragmented rhizomes.Shallow cultivation is not advised (BC Ministry ofAgriculture, Food and Fisheries 1996). Mowing beforespore production can reduce spread potential.

Fire: Burning of fertile stems can prevent sporeproduction but will not injure the deeply buriedrhizomes.

Herbicides: Few herbicides are registered to controlhorsetail. Dichlobenil is used for control in woodyornamentals, orchards, nurseries, berries, andshelterbelts. Amitrol provides control in non-croppedareas and shelterbelts, and MCPA formulations providetopgrowth control in grass pastures and cereals (BCMinistry of Agriculture, Food and Fisheries 1996).Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Improved drainage and vigorous,perennial grass cover will reduce horsetail in pasturesand hayfields. Mulching with porous landscape fabricsor black plastic effectively controls this plant, butsawdust or bark mulches are ineffective (BC Ministryof Agriculture, Food and Fisheries 1996).


65

Integrated Management SummaryThis is a dominant native plant in manyriparian ecosystems in BC and an importantfood source for geese and other waterfowl.Management should consider the context of theplant on the landscape. Herbicides and mowingcan be effective. Grazing management onprivate pasture should maintain perennial plantcommunities that can compete with thisspecies.

Management ________________________________________

References __________________________________________



Flower: Inflorescences aredense, clover-like heads, 1.5–4.0

cm wide, with violet-blue to purple flowerson the end of long, leafless stalks.

Seeds/Fruit: Seeds are 5–6 mm long, 4-angled, and densely hairy(Douglas et al. 1998).

Leaves: Basal leaves arecoarsely toothed, whilestem leaves are oppositeand feather-shaped.Lower leaves are 10–25cm long but are smallerhigher on the plant.

Stems: Stems are erect, hairy, and grow 0.3–1.3 m tall.

Roots: Well-developed woody taproot, oftenbranched below the soil.

Seedling: The cotyledons (seed leaves)are club-shaped, 15 mm long, and 5 mmwide. The first leaves are rounded withwavy margins and have scattered whitehairs. Later leaves become lobed(Royer and Dickinson 1999).

Similar Species

Exotics: Caucasian scabiosa (Scabiosa caucausia),an ornamental perennial for gardens, has a similarappearance to field scabious.

Natives: None.

Agricultural: Competes with forage stands and nativepastures, causing declines in hay production andpasture carrying capacity. Once established, it isdifficult to eradicate.

Ecological: Plants establish easily along roadsides anddisturbed areas and are capable of invading undisturbedplant communities (BC Ministry of Agriculture, Foodand Fisheries. Undated).

Human: This plant is sometimes grown as anornamental and butterfly attractant. It has a high oilcontent and is being considered as a source for high-performance lubricants and certain dietary fats.

FIELD SCABIOUS

Knautia arvensis (L.) Coult.Family: Dipsacaceae (Teasel).

Other Scientific Names: Scabiosa arvensis.

Other Common Names: Blue buttons, pincushion.

Legal Status: Regional Noxious: Kootenay-Boundary, Thompson-Nicola, Bulkley-Nechako.


66


General requirements: Adapted to nutrient-rich andmoderately moist to dry loam soils (BC Ministry ofAgriculture, Food and Fisheries. Undated. It is foundon roadsides, pastures, and fields at mid-elevations.

Distribution: This plant is absent from VancouverIsland and the Lower Mainland but is present in allother agricultural reporting regions in the province. It is

most troublesome in the Kootenays, Okanagan,Thompson, and Omineca regions.


Life cycle: Life cycle in BC not described. Initiallyproduces a rosette of basal leaves then sends upflowering shoots.


Impacts ____________________________________________

Seed production: A single plant can produce up to2,000 seeds.

Seed bank: Seeds remain viable in the soil for manyyears.

Dispersal: Most seeds fall from the plants, but otherscan be spread by birds and human activities.


BC Ministry of Agriculture, Food and Fisheries.Undated. Plant Industry Branch, Crop ProtectionProgram. Integrated Weed Management—FieldScabious. Fact Sheet.

Douglas, G. W., G. B. Straley, D. Meidinger, and J.Pojar. 1998. Illustrated Flora of British Columbia. Vol.1: Gymnosperms and Dicotyledons (Aceraceae throughAsteraceae). Province of British Columbia.


Biocontrol: None.

Mechanical: Cut or mow pastures before seed-set.Cultivation can manage this weed. Heavily infestedpastures and hayfields can be cultivated and rotated toan annual crop.


Herbicides: Picloram and metsulfuron-methyl provideexcellent control. Picloram can be applied spring orautumn, while metsulfuron-methyl should be applied toactively growing plants up to the early flower budstage. Consult the most recent edition of BC Ministryof Agriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Small infestations of immatureplants can be hand-pulled. Seed production can be

reduced by cattle grazing early in the season, but theplant becomes unpalatable as it produces floweringstalks. Maintain vigorous perennial plant communitiesand seed disturbed sites to provide ground cover andcompetition.


67

Integrated Management SummarySeed production must be prevented to managethis weed. This can be done by grazing ormowing plants before they flower or byapplying appropriate herbicides.

Management ________________________________________

References __________________________________________


Growth form: Winterannual forb.

Flower: Flowers grow inracemes, which lengthen when infruit. These racemes may grow up toone-half the total height of the plant(FEIS 1996). The petals are yellowto greenish yellow and verysmall.

Seeds/Fruit: Seeds are bornein linear pods that are 11–33mm long.

Leaves: Leaves are alternate,2–3 times pinnately compound.

Stems: Mature plants are 0.3–1.0 m tall.

Roots: Flixweed has a slender taproot.

Seedling: Narrow, stalked seed leaves(cotyledons).

Similar Species


Natives: Tansy mustard (Descurainiapinnata) is easily confused with flixweed but hasleaves that are only 1–2 times compound.

Agricultural: In cultivated areas, can crowd out cropplants and reduce yields (Mitich 1996).

Ecological: As an introduced species, flixweed hasspread very rapidly across portions of the inter-mountain West (Morishita 1991).


FLIXWEED

Descurainia sophia (L.) Webb exPrantlFamily: Brassicaceae (Mustard).


Other Common Names: Flixweed tansymustard, herb-sophia, fine-leaved hedge mustard.



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Impacts ____________________________________________


General requirements: Flixweed is found growing indisturbed habitats, fields, roadsides, and logged-overforests. It grows on a wide variety of soil types, but itis most abundant on dry, disturbed sites. It is oftenfound along roadsides and ditches where mineral soilhas been exposed (FEIS 1996).

Distribution: Frequent throughout BC at low- to mid-elevations and present in all agricultural reportingregions except the Queen Charlotte Islands and

adjacent coast (Douglas et al. 1998). It is commonthroughout North America.


Life cycle: Flixweed is an early-blooming winterannual or biennial and is one of the first weeds toappear in the spring. Flowering occurs from Marchthrough July, depending on geographic location.Flixweed spreads by seeds from early to late summer.Flixweed is an early seral species that quickly invades

areas of exposed mineral soil with reduced plant cover.It can survive in dense stands for a few years ifundisturbed but is generally replaced by other seralspecies (FEIS 1996). In later seral stages, flixweedcompetes poorly with perennial grasses and forbs.


Seed production: Large plants can produce as many as700,000 seeds (Rutledge and McLendon. Undated).

Seed bank: The seeds can remain viable for up to 3years (Morishita 1991).

Dispersal: Seeds are mucilaginous when wet, whichmay facilitate dispersal by animals or increaseadherence to soil particles (FEIS 1996).




Mitich, L. W. 1996. Intriguing world of weeds,flixweed (Descurainia sophia). Weed Technology 10:974–977.

Morishita, D. W. 1991. Dalmatian toadflax, yellowtoadflax, black henbane, and tansy mustard: Importance,distribution, and management. In L. F. James, J. O.Evans, M. H. Ralphs, and R. D. Child, eds. NoxiousRange Weeds. Boulder, CO: Westview Press.


Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Flixweed. Weeds of the West.Western Society of Weed Science,in cooperation with the WesternUnited States Land Grant UniversitiesCooperative Extension Services,Newark, CA.

Biocontrol: None.

Mechanical: Can be managed through cultivation orhand-pulling in the autumn or early spring as long asthe rosettes are small.

Fire: Plants are killed by fire at all stages, but seedsreadily colonize burned areas (FEIS 1996).

Herbicides: Metsulfuron-methyl, chlorsulfuron, and2,4-D all provide management of flixweed in the US(Morishita 1991). Herbicides should be applied duringseedling growth stage for effective management(Whitson et al. 1996). Consult the most recent editionof BC Ministry of Agriculture, Food and FisheriesCrop Production Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Prevent new infestations byminimizing disturbance and seed dispersal, eliminatingseed production, and maintaining native communities.


69

Management ________________________________________

References __________________________________________

Integrated Management SummaryLand management practices that maintainperennial grass communities will prevent thespread of flixweed. It can be managed byeliminating seed production until the soil seedbank is depleted. Cut, pull, or treat plants withherbicide prior to seed-set. Seed disturbedareas with perennial grasses to providecompetition.

Growth form: Perennial shrub.

Flower: Yellow, pea-likeflowers, 15–20 cm long,

borne on velvety, short stalks. Flowersusually appear singly but may be insmall clusters.

Seeds/Fruit: Flattened pods aredark (black, grey, or brown) andhairy, about 10–20 mm long, withseveral seeds in each pod.

Leaves: The leaves are alternate anddeciduous. Leaflets are arranged inthrees on young plants but arereduced to stiff scales or spines inmature plants. The spines arestiff, grooved, and branched,1.5–2.5 cm long.

Stems: Mature shrubs grow 1–3 m tall, usually with asingle, densely branched, erect stem. Branches are 5-angled, greenish with sparse black hairs, and tippedwith spines (Douglas et al. 1999).

Roots: Deep taproot and lateral fibrous roots justbelow the soil surface. Adventitious roots may form onbranches in contact with the ground.


Similar SpeciesExotics: Resembles Scotch broom (Cystius scoparius),another densely branched, medium to tall shrub with 5-angled stems and yellow, pea-like flowers that grows insimilar habitats, but Scotch broom has no spines.

Natives: Ulex are not native to North America.

Agricultural: Present in some pastures on VancouverIsland.

Ecological: This pioneer species invades disturbedhabitats, where it competes with native vegetation,reduces access for recreation, increases fire hazard, and

has the potential to impair forest regeneration in loggedareas. It has been problematic in some cut-blocks onVancouver Island.

Human: Originally used for stock fodder, for stock-proof hedgerows, and as an ornamental.

GORSE

Ulex europaeus L.Family: Fabaceae (Pea).


Other Common Names: Furze, whin, prickly broom.



70

Impacts ____________________________________________



General requirements: In BC, grows on dry, open,sandy or rocky clearings, old fields, cut banks, coastalbluffs, logged areas, flood plains, roadsides, and rights-of-way. Gorse occurs at low elevations with mildwinters and relatively dry, cool summers. It tolerates awide range of soils from sands to clays and is adaptedto low fertility. It grows best on acidic soils.

Distribution: Most common on southern VancouverIsland near Victoria, but populations occur on PenderIsland, West Vancouver on the Mainland, and

Skidegate on the Queen Charlotte Islands.

Historical: Introduced from Europe. Gorse hadescaped cultivation as early as 1883 in the Victoria area(Macoun 1883).

Life cycle: Plants flower in spring and autumn, andmost seedlings emerge in late spring, summer, orautumn. Germination is highest in open, unshadedareas. Plants grow rapidly for the first 15 years, andsome plants can live up to 45 years.


Seed production: Seed production is variable,depending on crowding, plant size, habitat, andweather conditions. Annual production can average500–600 seeds/m2.

Seed bank: More than 100 million seeds mightaccumulate in the seed bank under a continuous,mature stand of gorse (Meeklah 1979). Gorse seeds

have hard coats and can persist in the soil 25–40 years.

Dispersal: The maturing seed pods explode anddisperse seeds at least a meter from the parent. Ants,animals, birds, machinery, and water can all dispersethe seeds. Water is an especially important dispersalmechanism in the province, since many populationsgrow near the sea.


Biocontrol: A number of agents are used for managinggorse in different areas of the world, including thegorse seed weevil (Exapion ulicis), gorse spider mite(Tetranychus lintearius), shoot-tip moth (Agonopterixulicitella), and gorse thrips (Sericothrips staphylimus).The gorse spider mite appears promising since it is ableto reduce gorse vigour and increase mortality bysucking plant juices. It is unlikely to eradicate theshrub but probably could reduce the population totolerable levels. No biocontrol agents are currentlyapproved for release in Canada.

Mechanical: Manual cutting and mechanical controlhave been effective in controlling small gorseinfestations or on larger areas that are accessible withequipment. Since manual cutting can target individualplants, this technique can be valuable in sensitivehabitats such as riparian areas or where gorse isinterspersed with rare species. It may be the onlycutting method possible on steep and undulatingterrain. Specialized machinery has been used to cut andcrush gorse on large, accessible sites on VancouverIsland. Gorse sometimes coppices after cutting, andmechanical control can stimulate germination.

Fire: Fire can reduce above-ground portions of maturegorse shrubs, kill seedlings, destroy viable seeds on theplant, and reduce seeds in the soil seed bank. Unlessfires are very intense, however, plants can re-sproutfrom the base and more deeply buried seeds remainviable. Usually fire is combined with othermanagement practices such as grazing, herbicideapplication, or seeding native forages to achieve long-term control. Fire has not been widely used to controlgorse in the province, although it may be a useful toolon a site-specific basis.

Herbicides: Few herbicides have been tested andapproved for gorse in BC. Limited trials using 2,4-Dhave had variable results. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, read thelabel for full use and precautionary instructions.

Cultural/Preventive: Goats and sheep control gorsethrough browsing and trampling. Best results areachieved with intensive management and browsingyoung, un-hardened plants. Seeding to competitiveperennial grasses and forbs may reduce seedlingsurvival, especially if fertilizers are applied.


71

Integrated Management SummaryLong-term management will likely result froman integrated management program. Gorse hasbeen effectively controlled on forestland in NewZealand by using a combination of burningfollowed by herbicide applications, althoughthese treatments may have limited application inBC, considering the current distribution of theplant. Other treatment combinations haveintegrated machinery, herbicides, sowing,domestic forages, and grazing before plantingsites to crop trees. Introduction of biocontrolagents, such as the gorse spider mite, will alsocontribute to gorse control.

Management ________________________________________


72

Carey, J. B., J. J. Kells, and K. A. Renner. 1993.Common weed seedlings of Michigan. Department ofCrop and Soil Sciences, Michigan State UniversityExtension. Bulletin E-1363.http://www.msue.msu.edu/msue/iac/e1363/e1363.htm[27 Oct 99].

Douglas, B. J., A. G. Thomas, I. N. Morrison, and M.G. Maw. 1985. The biology of Canadian weeds. 70.Setaria viridis (L.) Beauv. Canadian Journal of PlantScience 65: 669–690.

Forcella, F., and K. R. Banken. 1996. Relationshipsamong green foxtail (Setaria viridis) seedlingdevelopment, growing degree days, and time ofnicosulfuron application. Weed Technology 10: 60–67.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Green foxtail. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

References __________________________________________


73


Flower: The flowers arecylindrical with crowded

spikelets that are subtended by 6–10long, yellowishbristles (Whitsonet al. 1996).

Seeds/Fruit: Seedsare oval, greenish to dark brown.

Leaves: The flattened leaf blades areusually less than 15 cm long. Theleaf sheath is roughened andhairless.

Stems: Mature plants are 0.3–1.0m tall, with erect stems thatbranch at the base (Whitson etal. 1996).

Roots: Short, fibrous roots.

Seedling: Leaf blades are hairless, as is the leaf sheath,except for short hairs along margins. The leaf lacksauricles and has a hair-like ligule (Carey et al. 1993).

Similar Species

Exotics: Green foxtail can be distinguished fromyellow foxtail (Setaria glauca) by the lack of long,twisting hairs on the upper surface of the leaf bladenear the base. Green foxtail can be distinguished frombur bristlegrass (Setaria verticillata) by the presence oflong hairs on the axis of the flowers (rachis) and by theforward-facing barbs of the bristles.


Agricultural: A nuisance in cultivated fields andirrigated valleys, the plant can be a serious problem inspring-seeded alfalfa, small grain, and row crops(Whitson et al. 1996). Green foxtail can cause yieldreductions, cleaning costs, and expensive control costs,

and it is also reported to have allelopathic effects oncabbage seedlings (Douglas et al. 1985).



GREEN FOXTAIL

Setaria viridis (L.) Beauv.Family: Poaceae (Grass).


Other Common Names: Green bristlegrass, pigeongrass, wildmillet.



74

Impacts ____________________________________________

Habitat and Ecology __________________________________General requirements: Green foxtail is commonlyfound in field crops (especially corn), vegetables,lawns, gardens, and disturbed habitats along roadsidesand streams. It is adapted to moist, medium- to coarse-textured soils.

Distribution: Found throughout BC and commonthroughout North America. It is present in allagricultural reporting regions and considered a majorconcern in the Peace River district.


Life cycle: A summer annual that overwinters as a seedon or below the soil surface. It generally emerges inearly spring following periods of high rainfall.Flowering occurs from July to September, dependingon geographic location, and seeds can mature within 2weeks of flowering. Seeds readily fall from the flowerstructures when mature (Douglas et al. 1985).



Seed production: Typically produces 5,000–12,000seeds/plant; however, the number of seeds/plant ishighly dependent upon the size of the plant, and someplants may produce up to 34,000 seeds.

Seed bank: Seeds can remain viable for up to 6 years(Douglas et al. 1985).

Dispersal: Seeds may be distributed by human activity,animals, birds, and water (Douglas et al. 1985).



Douglas, B. J., A. G. Thomas, I. N. Morrison, and M.G. Maw. 1985. The biology of Canadian weeds. 70.Setaria viridis (L.) Beauv. Canadian Journal of PlantScience 65: 669–690.

Forcella, F., and K. R. Banken. 1996. Relationshipsamong green foxtail (Setaria viridis) seedlingdevelopment, growing degree days, and time ofnicosulfuron application. Weed Technology 10: 60–67.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Green foxtail. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: None.

Mechanical: In natural areas, green foxtail could bemowed to eliminate seed production. However, sinceseeds already in the soil may remain viable for 6 years,repeated treatments are necessary to deplete the seedbank.


Herbicides: On rangeland, glyphosate has beeneffective when green foxtail is 5–10 cm tall. (Douglaset al. 1985). Numerous herbicides are registered forcontrol in various crop commodities. Consult the mostrecent edition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Prevent new infestations byminimizing disturbance, eliminating seed productionand dispersal, and maintaining vigorous perennialnative communities. Clean machinery, vehicles, andequipment. Manage grazing or other land uses tomaintain vigorous perennial communities.


75

Integrated Management SummaryFocus control methods toward eliminating seedproduction until the soil seed bank is depleted.Cut, pull, or treat plants with herbicide beforeseed-set, and repeat treatments as necessary.

Management ________________________________________

References __________________________________________


Flower: The flowers resemble those of thepotato and tomato and have

5 white petals and an enlarginggreen calyx (Whitsonet al. 1996).

Seeds/Fruit: As thefruit matures, the calyxcups the lower half ofthe greenish oryellowish berry-likefruit (Whitson et al.1996).

Leaves: Leaves arealternate, egg-shaped(ovate), tapered to thetip, and covered withglandular hairs. May feelsticky when handled.

Stems: Mature plants are 10–90 cm tall, spreading, andfreely branching. The stems are light green and roundor slightly angular with glandular hairs.

Roots: No information available.

Seedling: The first true leaves of hairy nightshade havewavy edges and prominent veins. The leaveshave numerous fine, short hairs, especiallyalong the underside of the main vein(Calweed 1997).

Similar Species

Exotics: Hairy nightshade is distinguishable fromblack nightshade (Solanum americanum var.nodiflorum) by the hairy appearance of its foliage andthe covering calyx on top of the berry, which covershalf of the fruit.


Agricultural: A common weed of disturbed habitatsand cultivated fields. Berries frequently become mixedwith agricultural crops, which decreases their quality.The plants produce a sticky substance that can clogagricultural equipment such as combine screens androtors (Basset and Munro 1985). The plant contains

toxic alkaloids, especially in the berries, that canpoison cattle, sheep, goats, pigs, ducks, and chickens(Basset and Munro 1985; Whitson et al. 1996).


Human: Berries are considered toxic.

HAIRY NIGHTSHADE

Solanum physalifolium Rusby Family: Solanaceae (Nightshade).

Other Scientific Names: Solanum sarrachoides.

Other Common Names: Hoe nightshade.



76

Impacts ____________________________________________



General requirements: In BC, found at low- to mid-elevations on dry to moderately dry sites on a varietyof soils and climates. Commonly found on disturbedsoils such as roadsides, rights-of-way, and overgrazedrangeland, as well as cultivated fields, flowerbeds, andvegetable gardens. Hairy nightshade has been found onsandy/gravelly soils to fertile cultivated soils but seems

to be adapted to soils that are high in nitrogen.

Distribution: Widely distributed in the US butinfrequent in southern parts of BC (Douglas et al.2000).

Historical: Introduced from South America.

Life cycle: Typically, hairy nightshade plants begin to

germinate in the spring and continue to germinatethrough the summer. Flowering begins by mid-June,and berries mature 4–5 weeks later. Full sunlight isneeded for maximum flower initiation (Basset andMunro 1985).


Seed production: Capable of producing 2,500–5,000seeds/plant (Basset and Munro 1985).


Dispersal: Berries and seeds are dispersed by rodents,birds, livestock, and humans, and along watercourses.

Hybridization: Reported to be able to hybridize withother closely related nightshades (Basset and Munro1985).

Basset, I. J., and D. B. Munro. 1985. The biology ofCanadian weeds. 67. Solanum ptycanthum Dun., S.nigrum L. and S. sarrachoides Sendt. CanadianJournal of Plant Science 65: 401–414.

Calweed Database. 1997. California Noxious WeedControl Projects Inventory. Natural Resource ProjectsInventory, Information Center for the Environment,University of California, Davis.http://endeavor.des.ucdavis.edu/weeds/ [6 Jan 99].

Douglas, G. W., D. Meidinger, and J. Pojar, eds. 2000.Illustrated Flora of British Columbia. Vol. 5:Dicotyledons (Salicaceae through Zygophyllaceae) andPteridophytes. Province of British Columbia.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Hairy nightshade. Weeds of the West. Western Societyof Weed Science, in cooperation with the WesternUnited States Land Grant Universities CooperativeExtension Services, Newark, CA.

Biocontrol: None.

Mechanical: No information available.


Herbicides: Post-emergence application of dicambahas been effective. Atrazine, cyanazine, or linuron willalso manage small seedlings (Basset and Munro 1985).Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Hand-pulling can be effective onsmall populations, especially before a seed bankdevelops, but it may take several years to accomplisheradication.


77

Integrated Management SummaryIntegrated management should focus oneliminating seed production and depleting theseed bank. Use mechanical or chemicalmethods to prevent seed production, and reviseland management practices to ensure themaintenance of a vigorous perennial plantcommunity.

Management ________________________________________

References __________________________________________


Flower: Flowers occur in dense clustersfrom leaf axils. Flowers can be purple, pink,

white, or pale yellow with dark markings (Douglas etal. 1999). Petals are fused into a tube with 2 lips. Thesepals fuse to form a spine-tipped calyx that elongatesas the fruit matures (Royer and Dickinson 1999).

Seeds/Fruit: Four clustered nutlets are produced fromeach flower. Nutlets are egg-shaped, 3–4 mm long, andsmooth (Douglaset al. 1999).

Leaves: Oppositeleaves are stalkedand egg-shapedto lance-like, andhave large, roundedteeth and pointedtips. Leaves areprominently veined andcovered in bristly hairs.

Stems: Branched stems grow 15–100 cm tall and aresquare with bristly hairs. Stems are swollen below theleaf nodes, where stiff, downward-pointing hairs arefound (Royer and Dickinson 1999).

Roots: Fibrous taproot.

Seedling: Rounded cotyledonshave a notch at the tip and 2pointed lobes at the base. The firstleaves are opposite, coarselytoothed, and prominently veined(Royer and Dickinson 1999).

Similar Species

Exotics: Hemp-nettle has square stems like most of themint family, but its prickly hairs, the spiny calyx, andswollen stems below the joints distinguish this plantfrom all others (Frankton and Mulligan 1970).

Natives: Same comment as for exotics.

Agricultural: Infests grain fields, canola, and pastures.It reduces yield and carrying capacity throughcompetition with crops for nutrients and moisture. Itssmall seeds contaminate small grains and are difficultto remove. It acts as an alternate host for a potatofungus and several nematodes.

Ecological: Commonly grows in disturbed habitatssuch as roadsides, barnyards, and gardens but also isfound in wooded areas and forest margins.


HEMP-NETTLE

Galeopsis tetrahit L.Family: Lamiaceaea (Mint).


Other Common Names: Dog nettle.



78

Impacts ____________________________________________



General requirements: Hemp-nettle tolerates a widerange of temperatures and soil types but appears bestadapted to moist soils. It is most abundant on moist,rich, black soils. In BC this weed is found in cultivatedfields, pastures, roadsides, disturbed habitats, and openforests.

Distribution: Present in all agricultural reportingregions. It grows to the northern limits of agriculture inevery Canadian province but is of greatest concern inparts of the Prairie provinces (Frankton and Mulligan1970). Small populations are found in Washington,Idaho, and Montana (Royer and Dickinson 1999).


Life cycle: Seeds germinate in early spring afteroverwintering in the soil. Additional seeds cangerminate throughout the growing season if conditionsare favourable. Flowering occurs from July toSeptember, depending on geographic location. Late-emerging seedlings may not mature because seedsoften are shed before they mature.


Seed production: A single plant can produce about400 plants (O’Donovan and Sharma 1987).

Seed bank: Seeds can remain viable in the soil forseveral years (Royer and Dickinson 1999).

Dispersal: Primarily by wind and through agriculturaloperations such as seeding and harvesting. Seed canalso be spread through contaminated crop seed andlivestock feed.

Hybridization: Hemp-nettle is believed to be a hybridof Galeopsis pubescens and Galeopsis speciosa(O’Donovan and Sharma 1987).

Douglas, G. W., D. Meidinger, and J. Pojar, eds. 1999.Illustrated Flora of British Columbia. Vol. 3.Dicotyledons (Diapensiaceae through Onagraceae).Province of British Columbia.


O’Donovan, J. T., and M. P. Sharma. 1987. Thebiology of Canadian weeds. 78. Galeopsis tetrahit L.Canadian Journal of Plant Science 67: 787–796.


Biocontrol: None.

Mechanical: Spring cultivation can control seedlingsas they emerge. Repeated cultivation of summerfallowor other non-seeded areas may reduce populations. Clipforages with hemp-nettle infestations before seed-set.


Herbicides: Hemp-nettle is resistant to 2,4-D. Anumber of herbicides are registered for control orsuppression of hemp-nettle in various crops. Consultthe most recent edition of BC Ministry of Agriculture,Food and Fisheries Crop Production Guides forspecific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Contaminated crop seed andlivestock feed contribute to the dispersal of the plant.

Monitor feeding areas for new weeds. Clean equipmentbefore leaving an infested site. Delayed seeding willallow early-growing seedlings to be removed bycultivation. Plant companion crops with slow-growingforage crops.


79

Integrated Management SummaryA combination of tillage and springapplications of herbicides appears to be themost effective combination of treatments tocontrol this weed. Preventive actions, such ascleaning equipment and farm machinery, willhelp reduce the spread of this weed.

Management ________________________________________

References __________________________________________

Growth form:Biennial (rarelyperennial) forb.

Flower: White flowers 4–6mm long with deeplynotched petals carriedon slender stalks.Sepals are hairy andsoon drop off.

Seeds/Fruit: Flattened ovalseed pods are 5–8 mm long,have star-like hairs, andare held close to thestem (BC Ministryof Agriculture,Food and Fisheries1998). The styles remain,making a prominent point on thetips. Seed pods are chambered, witheach chamber containing 3–7 seeds.Seeds, 2–3 mm long, are aligned in rowsin the chambers (Douglas et al. 1998).

Leaves: All leaves are grey with star-shaped hairs.Basal leaves are 3–5 cm long with slender stalks. Stemleaves face upward, pressed close to the stem. Lowerstem leaves have short stalks, but stalks arelacking higher on the stem.

Stems: Erect and branched, 0.3–1.1 m tall,and covered with star-shaped hairs.

Roots: Slender taproot.


Similar Species

Exotics: Pale alyssum (Alyssumalyssoides), desert alyssum (Alyssumdesertorum), and wall alyssum (Alyssum murale)resemble hoary alyssum, but they are smaller plantswith much smaller seed pods (at most 4 mm long) thatcarry only 1–2 seeds/chamber. Wall alyssum and desertalyssum have yellow flowers. Hoary alyssum is alsosimilar to false flaxes (Camelina sp.) but differs inhaving pods on erect stems that touch, or nearly touch,the stem (Frankton and Mulligan 1970).

Natives: None similar.

Agricultural: Tends to increase in forage cropsfollowing drought or winterkill. Horses consuming thisplant may be troubled with fever, limb edema, andlaminitis.

Ecological: Establishes in dry, disturbed habitats, suchas roadsides and railway embankments.

Human: None known.

HOARY ALYSSUM

Berteroa incana (L.) DC.Family: Brassicaceae (Mustard).



Legal Status: Regional Noxious: Kootenay-Boundary.


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Impacts ____________________________________________



General requirements: Most common on dry sandy orgravelly soils. Grows on meadows, pastures, hayfields,dry fields, roadsides, embankments, and otherdisturbed habitats.

Distribution: Present in south-central and southeastern

BC in the Okanagan, Thompson, and Kootenayagricultural regions. Present across southern Canada.


Life cycle: Can behave as an annual, biennial, orperennial. The plant emerges in early spring and

continues to flower and produce seed until frost.Flowering period is from June to September. Perennialform overwinters as a rosette.






Douglas, G. W., D. Meidinger, and J. Pojar. 1998.Illustrated Flora of British Columbia. Vol. 2:Gymnosperms and Dicotyledons (Balsaminaceaethrough Cuscutaceae). Province of British Columbia.


Biocontrol: No agent available.

Mechanical: Small populations are killed by hand-pulling or hoeing. Mowing can prevent seedproduction.


Herbicides: Most commonly 2,4-D is used, butdicamba and glyphosate also are effective. Apply inspring or autumn to actively growing plants. Consultthe most recent edition of BC Ministry of Agriculture,Food and Fisheries Crop Production Guides forspecific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Grazing or crop managementshould aim to promote a healthy and competitiveforage stand to resist invasion.


81

Management ________________________________________

References __________________________________________

Integrated Management SummaryEarly detection is important to prevent largeinfestations. Hand-pull plants before theymature in order to prevent seed-set andestablishment of a seed bank. Apply herbicidesto control seedlings and mature plants. Seeddisturbed areas to perennial grasses and forbsto provide cover and competition against thisweed.

Growth form:Perennial forb.

Flower: Numerouswhite flowers with 4 petals givethe plant a white, flat-toppedappearance.

Seeds/Fruit: Seed capsulesare heart-shaped and contain2 reddish brown seeds.

Leaves: Leaves are alternate,4–10 cm long, blue-green incolour, and lance-shaped.Lower leaves are stalked,while the upper leaveshave 2 lobes clasping thestem.

Stems: Mature hoary cress plants are up to 50 cm tallwith erect stems.

Roots: Roots are rhizomatous and usually occur at adepth of 75–80 cm but have been recorded to penetrateto 9 m in the US Pacific Northwest (FEIS 1996).


Similar Species

Exotics: Globe-pod hoary cress(Cardaria pubescens) is infrequent insouth-central BC (Douglas et al. 1998). Perennialpepperweed (Lepidium latifolium) is a regional noxiousweed in the province.

Natives: Rosettes of gumweed (Grindelia squarrosa)are similar and found in similar habitats.

Agricultural: Generally considered unpalatable tolivestock. Often spread as a contaminant of alfalfa hay.

Ecological: Once established, hoary cress is a highlycompetitive weed and spreads primarily by roots. It can

be highly competitive with native vegetation onrangelands.


HOARY CRESS

Cardaria draba (L.) Desv.Family: Brassicaceae (Mustard).


Other Common Names: Whitetop, heart-podded hoary cress,pepperweed.

Legal Status: Regional Noxious: Columbia-Shuswap, NorthOkanagan, Thompson-Nicola.


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Impacts ____________________________________________



General requirements: Hoary cress grows at low- tomid-elevations on the coast and in the Interiorgrassland and forest regions of BC, where it is foundon dry roadsides, fields, and disturbed habitats(Douglas et al. 1998). It is typically found on open,unshaded, disturbed ground. Hoary cress grows well onalkaline soils that are wet in late spring and does betterin areas with moderate amounts of rainfall. OutsideBC, it is widespread in fields, disturbed habitats,meadows, pastures, and croplands, and along roadsides(FEIS 1996).

Distribution: Hoary cress is infrequent in southern BC(Douglas et al. 1998), but is considered a majorconcern in the Okanagan and Thompson agriculturalreporting regions and is present in the Kootenay andCariboo. It is widespread in the US except along thesouthern boundary of the western and south-centralstates (USDA 1971).


Life cycle: The root system of hoary cress consists ofvertical and horizontal roots from which new rosettesand flowering shoots arise (Mulligan and Findlay 1974).

Plants emerge in very early spring. The first leavesappear above ground 5–6 weeks after planting (Mulliganand Findlay 1974; FEIS 1996). During this period, thefirst leaves emerge and form a loose rosette (Mulliganand Findlay 1974; FEIS 1996). Stems arise from thecentre of each rosette in late spring (FEIS 1996). Plantsflower from May to June and are pollinated by insects.Hoary cress plants set seed by midsummer (Whitson etal. 1996). If conditions are favourable, a second crop ofseeds can be produced in the autumn (Sheley and Stivers1999). When unimpeded by competition from otherplants, a single plant can spread over a 3.5 m2 area inone year (FEIS 1996).


Seed production: One plant can produce 1,200–4,800seeds.

Seed bank: 84% of seed produced are viable the firstseason (Mulligan and Findlay 1974; FEIS 1996).Buried seeds can remain viable for 3 years (Sheley andStivers 1999).




CSU Cooperative Extension. 1998. Whitetop. ColoradoState University Cooperative Extension TriRiver Area.http://www.colostate.edu/Depts/CoopExt/TRA/whtop.html [11 Nov 98].


Mulligan, G. A., and J. N. Findlay. 1974. The biologyof Canadian weeds. 3. Cardaria draba, C. chalapensis,and C. pubescens. Canadian Journal of Plant Science54: 149–160.

Biocontrol: None. Sheep grazing may manage hoarycress.

Mechanical: Mowing 2–3 times a year for severalyears may slow the spread and reduce seed production.Mowing should be conducted during the bud stage andrepeated when the plants re-bud.

Fire: Fire may enhance hoary cress populations bysetting back other vegetation because the plant rapidlyre-sprouts from rhizomes or establishes from seeds(FEIS 1996).

Herbicides: Spring applications of metsulfuron-methyland chlorsulfuron have been effective in the US whenthe plants still have green tissue (CSU 1998). It isimportant to use a non-ionic surfactant with theherbicide (Sheley and Stivers 1999). A combination of2,4-D and dicamba can also be effective when appliedduring the early pre-bud stage (CSU 1998).Glyphosate, applied during the flower stage, willprovide good control of hoary cress. Picloram does notcontrol hoary cress. Multiple herbicide applications areusually needed to provide lasting control. Consult themost recent edition of BC Ministry of Agriculture,Food and Fisheries Crop Production Guides forspecific recommendations. Before applying

herbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Cultivation alone will managehoary cress when tillage begins at flower bud stage andis repeated every 10 days throughout the growingseason (FEIS 1996). Also, nitrogen fertilization canincrease the growth of grasses and slow the rate ofhoary cress invasion (Sheley and Stivers 1999).


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Integrated Management SummaryHoary cress is usually managed withherbicides and less commonly by mowing.Management is difficult because of the plant’sdeep rhizomatous root system, abundant seedproduction, and the diversity of habitats inwhich it can survive (FEIS 1996). Mowingmay increase the effectiveness of subsequentherbicide application (Sheley and Stivers 1999)and may be even more effective if sites areseeded to perennial grasses.

Management ________________________________________

References __________________________________________


84

Sheley, R. L., and J. Stivers. 1999. Whitetop. In R. L.Sheley and J. K. Petroff, eds. Biology and Managementof Noxious Rangeland Weeds. Corvallis: Oregon StateUniversity Press.

US Department of Agriculture, Agricultural ResearchService. 1971. Common Weeds of the United States.New York: Dover Publications.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Hoary cress. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.


85

Growth form: Biennial or short-livedperennial forb.

Flower: Flowers are reddishpurple, with 5 petals, arranged inpanicles in the upper leaf axils.

Seeds/Fruit:The fruit iscomposed of 4nutlets, eachabout 7 mmlong (Powell etal. 1994).

Leaves: Leavesare alternate, 10–30 cmlong, 2–5 cm wide, rough,hairy, and lacking teeth orlobes. Basal leaves areelliptical to oblanceolate andtapered at the base.

Stems: The plant may produce a singleflowering stem or multiple stems/plant.The stem is erect, 0.3–1.2 m tall,and usually branched above.

Roots: A woody taproot.

Seedling: Seedlings emergeboth spring and autumn, and arosette develops in the firstyear.

Similar Species

Exotics: None.

Natives: Northernhound’s-tongue.Infrequent in BC,occurring in forestopenings in the lower montanezone (Douglas et al. 1998).

Agricultural: Hound’s-tongue on rangeland andpasture decreases forage available to grazing animals.The barbed seeds readily cling to hair, wool, and fur ofanimals. This can result in reduced sale value, stress onanimals, and veterinary costs if the burrs cause eyeirritation (Upadhaya et al. 1988). The plant containstoxic alkaloids that stop liver cells from reproducing.Animals may live 6 or more months after eating alethal dose. Plants have proven a problem in infested

hay, but standing plants are seldom grazed. Sheep aremore resistant to hound’s-tongue poisoning than cattleor horses.

Ecological: Hound’s-tongue is an early successionalspecies, but its impacts on biodiversity and forageproduction on rangelands have not been documented.

Human: Not recommended for human consumption,although medicinal properties are purported.

HOUND’S-TONGUE

Cynoglossum officinale L.Family: Boraginaceae (Borage).


Other Common Names: Dog bur, gypsy flower.



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Impacts ____________________________________________



General requirements: Hound’s-tongue grows fromgrasslands to low- and mid-elevation forests in BC. Itis associated with soil disturbance on dry sites on

pastures, roadsides, and logged-over forestland (Powellet al. 1994). It appears adapted to areas with alkalinesoils (Stubbendieck et al. 1995).

Distribution: Occurs primarily in the southern Interior.It is considered a major concern in the Kootenay,Okanagan, Thompson, and Cariboo agriculturalreporting areas. It is widely distributed in the US,where it grows on rangeland, pastures, abandonedcropland, roadsides, and disturbed habitats (Butterfieldet al. 1996).

Historical: Introduced from Eurasia, likely as acontaminant in seed.

Life cycle: A biennial or short-lived perennial thatproduces a rosette during the first year. During thesecond year (or subsequent years), the plant bolts andproduces seeds.


Seed production: Mature plants can produce up to2,000–4,000 seeds annually (Powell et al. 1994).

Seed bank: Seeds remaining on the parent plant mayremain viable for 2–3 years. Buried seed rarely survivemore than a year (Butterfield et al. 1996).

Dispersal: Seeds attach to clothing, livestock, andwildlife and can easily be spread great distances.


Butterfield, C., J. Stubbendieck, and J. Stumpf. 1996.Species abstracts of highly disruptive exotic plants.Jamestown, ND: Northern Prairie Wildlife ResearchCenter Home Page.http://www.npwrc.usgs.gov/resource/othrdata/exoticab/exoticab.htm [16 Jul 97].

Douglas, G. W., D. Meidinger, and J. Pojar. 1998.Illustrated Flora of British Columbia. Vol. 2:Gymnosperms and Dicotyledons (Balsaminaceaethrough Cuscutaceae). Province of British Columbia.


Sebastian, J. R., and K. G. Beck. 1995. Hound’s-tonguecontrol on Colorado rangeland with spring- or fall-applied herbicides. Research Progress Report of theWestern Society of Weed Science. pp. 11–12.

Biocontrol: Mogulones cruciger (weevil) was releasedin BC in 1998, and preliminary results indicate theinsect is having a significant impact on hound’s-tongue. Research continues on other specialized insectsas well. Two indigenous diseases, Erysiphe cynoglossiand Phoma pomorum, cause a mildew and brownlesions on the leaves, respectively.

Mechanical: Mowing plants before seed-set reducesthe seed production and may kill the plant.


Herbicides: In BC, excellent long-term control isachieved with picloram applied in spring, summer, orautumn. Dicamba provides good control applied eitherspring or autumn (Upadhaya and Cranston 1991).Spring applications of picloram, dicamba, andmetsulfuron-methyl have been more effective thanautumn treatments in the US (Sebastian and Beck1995). Glyphosate also controls actively growingplants. Consult the most recent edition of BC Ministryof Agriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Hand-pulling can be effective forsmall populations and especially before the plant setsseed. Clean cattle, horses, dogs, and yourself beforemoving from a hound’s-tongue–infested area. Checkvehicle for seeds.


87

Integrated Management SummaryHound’s-tongue can quickly form dense standson disturbed areas. Treat first-year plants withherbicides, or hand-pull plants. Mow boltedplants to eliminate seed production. Repeat thisprocess to exhaust the seed bank. Ensure thatareas where livestock congregate (such ascorrals and gates) are weed-free, especiallywhen the weed is in seed-set. Manage livestockto maintain a vigorous population of perennialplants to provide ground cover. Check people,vehicles, and dogs for seeds before you leavean infested area.

Management ________________________________________

References __________________________________________


88

Stubbendieck, J., G. Y. Friisoe, and M. R. Bolick.1995. Hound’s-tongue. Weeds of Nebraska and theGreat Plains. Lincoln: Nebraska Department ofAgriculture, Bureau of Plant Industry.

Upadhaya, M. K., and R. S. Cranston. 1991.Distribution, biology and control of hounds’-tongue inBritish Columbia. Rangelands 13 (3).

Upadhaya, M. K., H. R. Tilsner, and M. D. Pitt. 1988.The biology of Canadian weeds. 87. Cynoglossumofficinale. Canadian Journal of Plant Science 68:763–774

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Hound’s-tongue. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.


89

Growth form:Winter annual.

Flower:The seed head is5–10 cm long with5–10 spikelets(joints)/head.

Seeds/Fruit:Spikelets are 1.0cm long with 1–3viable seeds. Atmaturity, spikeletsseparate with asegment of thestem still attached(Whitson et al.1996).

Leaves: Leavesare alternate,simple, with a

flap-like appendage (auricle) at thebase, and a leaf blade 40–65 mmwide, with hairs.

Stems: Mature plants aregenerally 35–75 cm tall with oneto many tillers.

Roots: Short fibrous root system.

Seedling: No informationavailable.

Similar Species

Exotics: Similar in appearance towinter wheat (Triticum aestivum).


Agricultural: Jointed goatgrass has become a veryserious weed in winter wheat and other cereal crops. Itsgenetic similarity and similar growth characteristics towinter wheat make it very difficult to manage withoutadversely harming crop production. It also infestsrangeland surrounding wheat-growing areas throughout

the western US (Morishita 1998), but is not known as aproblem in BC.



JOINTED GOATGRASS

Aegilops cylindrica Host Family: Poaceae (Grass).

Other Scientific Names: Cylindropyrum cylindricum.

Other Common Names: Jointgrass.



90



General requirements: Grows on both cultivatedlands and rangelands. It is adapted to areas whereannual rainfall ranges from 60 to 125 cm.

Distribution: This plant is not currently known in BCbut is found throughout the western US (Lyon 1998) atelevations up to 1,800 m (including northern Idaho).

Historical: Possibly introduced from Turkey incontaminated wheat.

Life cycle: Flowers in early to mid-June, depending ongeographic location. Some seeds germinateimmediately after they are shed, but others can persistin the soil for years (Lyon 1998). Seeds usually

Impacts ____________________________________________

germinate from early August through October, but theycan also germinate in late spring and still mature iftemperatures are low enough.


Seed production: A single plant can produce up to 100spikes, 1,500 spikelets or joints, and up to 3,000 seeds(Lyon 1998).

Seed bank: Soil moisture plays an important role inseed viability and dormancy, but seeds rarely remainviable in the soil for over 5 years (Morishita 1998).



Beck, K. G., J. R. Sebastian, and P. L. Chapman. 1995.Jointed goatgrass (Aegilops cylindrica) and downybrome (Bromus tectorum) control in perennial grasses.Weed Technology 9: 255–259.

Lyon, D. J. 1998. Jointed goatgrass biology.http://www.ianr.unl.edu/jgg/billings/lyonbiol.htm [28Jul 98].

Morishita, D. W. 1998. Biology of jointed goatgrass.http://www.ianr.unl.edu/jgg/conf/morish2.htm [28 Jul98]

Stahlman, P. W. 1998. Jointed goatgrass controlmethods: A review.http://www.ianr.unl.edu/jgg/stahlman.htm [12 Nov 98].

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Jointed goatgrass. Weeds of the West. Western Societyof Weed Science, in cooperation with the WesternUnited States Land Grant Universities CooperativeExtension Services, Newark, CA.

Biocontrol: None.

Mechanical: Mowing can be effective if plants are cutafter flowering but before the seeds mature (Stahlman1998).

Fire: Fire can be an effective control under somecircumstances but soil surface temperature must exceed95o C for at least 60 seconds (Stahlman 1998). Fire hasbeen most effective in controlling jointed goatgrass asa post-harvest treatment on winter wheat stubble inWashington State but has been less successful as aspring treatment (Stahlman 1998).

Herbicides: No herbicide will selectively manage jointedgoatgrass in winter wheat because the 2 species are soclosely related genetically. Various combinations ofatrazine, hexazinone, metribuzin, or diuron have beeneffective in the US (Stahlman 1998) when fields are infallow. Jointed goatgrass is usually best managed whenplants are less than 10 cm tall. Applications of glyphosateat various rates have also been effective, especially whenthe plant is under 6 cm tall (Beck et al. 1995).

Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Management should aim toprevent the introduction of seed in the soil seed bankand to deplete viable seed in soil (Stahlman 1998).Jointed goatgrass seeds are difficult to distinguish fromwheat and are often spread by being planted withwheat or by uncleaned combines. Spread can beminimized by sowing jointed goatgrass-free seedwheat, covering trucks transporting contaminated grain,thoroughly cleaning machinery before moving frominfested to non-infested areas, processing contaminatedgrain before feeding to livestock, and not baling ortransporting contaminated straw to non-infested areas(Stahlman 1998).


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Integrated Management SummaryAn integrated management strategy shouldfocus on preventing the establishment of newinfestations in susceptible areas and depletingthe soil seed bank.

Management ________________________________________

References __________________________________________


Flower: Flowers are inconspicuous,stalkless in the axils of upper leaves, and

form short, dense, bracted spikes (Whitson et al. 1996).

Seeds/Fruit: Seeds are wedge-shaped, dull brown, slightlyribbed.

Leaves: Leavesare 2–6 cmlong, alternate,and lance-shaped. Theupper surface ofthe leaf is usuallysmooth, whilethe lowersurface iscovered withsoft hairs.

Stems: Mature plants are 0.3–1.5 m tall with numerousbranches. Stems are erect and simple to branched, andoften form pyramidal or rounded tops. Stems areusually hairy but are occasionally smooth.

Roots: Taproots generallypenetrate to depthsof 2.0–2.4 m.

Seedling: Noinformation available.

Similar Species

Exotics: Five-hook bassia(Bassia hyssopifolia) is easilydistinguished from kochia by the 5 hooked structureson each seed. This plant is infrequent in south-centraland southeast BC (Douglas et al. 1998).


Agricultural: Although palatable to livestock, kochiasometimes contains high nitrate levels and sulphatetoxicity (Whitson et al. 1996).

Ecological: Colonizes rapidly and may suppress othervegetation. An early successional plant on disturbed

sites and can dominate vegetation for the first 2 yearsfollowing disturbance (FEIS 1996). Kochia may spreadinto undisturbed sites when growing conditions areideal.


KOCHIA

Kochia scoparia (L.) Schrad.Family: Chenopodiaceae (Goosefoot).


Other Common Names: Summer cypress, burning bush, fireweed.



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Impacts ____________________________________________



General requirements: Locally common in dry areasof the Interior in roadsides, ditches, and disturbedhabitats (Parish et al. 1996), kochia is generally foundin open, unshaded areas on disturbed sites. It grows ona variety of soil types and is often found onsaline/alkaline soils (FEIS 1996). Kochia can also befound in grasslands, mixed-grass prairie, shortgrass

prairie, flood plains, riparian areas, sagebrush, anddesert shrub communities.

Distribution: Frequent in south-central BC but rare insouthwestern and northwestern regions (Douglas et al.1998). It is present in the Kootenay, Okanagan, andThompson agricultural reporting regions but isconsidered a major concern only to the Peace River. It

is found in all but some of the Atlantic provinces and iswidespread in the western US.


Life cycle: Seedlings emerge early in the spring.Flowering and seed production may occur from July toOctober. Kochia appears very responsive to elevatedsoil nitrogen levels. It often grows vigorously for 1–2years in abandoned fields until nitrogen is depleted.Kochia is rarely a problem in vigorous stands ofperennial grasses.


Seed production: Seed production can vary widelyamong individual plants from 5 seeds/plant to over50,000 seeds/plant. Typically, a single plant willproduce about 14,600 seeds/year.

Seed bank: Seeds are not persistent in the seed bankand decay in one year (FEIS 1996).

Dispersal: Primarily by breaking off at the stem andtumbling.



FEIS—Fire Effects Information System. 1996.Prescribed Fire and Fire Effects Research Work Unit,Rocky Mountain Research Station (producer). USForest Service. http://www.fs.fed.us/database/feis/ [12Mar 98]

Parish, R., R. Coupe, and D. Lloyd. 1996. Plants ofSouthern Interior British Columbia. Edmonton: LonePine Publishing/University of Alberta Press.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Kochia. Weeds of the West. Western Society of WeedScience, in cooperation with the Western United StatesLand Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: None.

Mechanical: Grazing or mowing alone will notmanage kochia or stop seed production (FEIS 1996).Small infestations can be pulled by hand.


Herbicides: Spring applications of dicamba,glyphosate, and a combination of metsulfuron-methyland dicamba have been effective for management inthe US (Whitson et al. 1996). Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Minimize disturbance and seed

dispersal, eliminate seed production, and maintainvigorous perennial plant communities. Seed disturbedareas to perennial grass to promote competition.


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Integrated Management SummaryIntegrated management should focus oneliminating seed production and depleting theseed bank. Combine herbicide or mechanicalremoval of rosettes with removal of seed headsfrom any plants that have bolted. Seeddisturbed areas to perennial grasses.

Management ________________________________________

References __________________________________________


Flower: Flowers arepink or purplish

and are carried in crowded,rounded, spike-like clusters atthe ends of the stems or fromthe leaf axils.

Seeds/Fruit: Seeds are black,shiny, smooth, and 2–3 mmlong. They are either 3-sided orlens-shaped.

Leaves: Basal leaves are absent. Lance-shaped leaves are alternate, 3–10 cmlong, and usually have a dark spot nearthe middle. The stalks are short andthick and a papery sheath at the base haslong hairs.

Stems: Stems are much branched and can beprostrate or erect, 0.2–1.0 m long.

Roots: Taproot.

Seedling: Smartweeds (lady’s-thumb) andknotweed (Polygonums) have a papery sheathwhere the leaf joins the stem.

Similar Species

Exotics: Green smartweed (Polygonum lapathafolium)also has the distinctive dark blotch on the leaves, but ithas white flowers and sticky yellow hairs on theunderside of the leaf and lacks long, bristly hairs on theleaf sheath.

Natives: Forms of lady’s-thumb that lack the typicaldark blotch can be confused with water-pepper(Polygonum hydropiperoides). Water-pepper hasrhizomes and the flowers are carried in slender racemes.

Agricultural: A common weed of cereals, oilseeds,vegetables, berries, and forages. It competes withcrops, causing yield reductions. Smartweeds (lady’s-thumb) can delay harvesting since the large, succulentplants are slow to dry.

Ecological: Occurs along roadsides and ditches and indisturbed areas, especially where moist or shady.Sometimes found in riparian areas, such as in moistmeadows and along lake or pond shorelines.


LADY’S-THUMB

Polygonum persicaria L.Family: Polygonaceae (Buckwheat).

Other Scientific Names: P. maculata, P. vulgaris.

Other Common Names: Spotted knotweed.



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Impacts ____________________________________________



General requirements: Found along roadsides andditches, on cultivated land, and in disturbed areas.

Distribution: Present in all agricultural regions but mostcommon in southwestern BC, becoming less frequent innorthern regions (Douglas et al. 1999). Commonthroughout southern Canada and the northern US.


Life cycle: Overwinters as seed. Germinates in springand completes its life cycle in one season.




Dispersal: Small seeds can be carried by water or wind.Seeds carried in mud can be carried on vehicles andequipment. Contaminated crop seed disperses the weedover long distances.

Hybridization: Not known.

BC Ministry of Agriculture, Food and Fisheries. 1998.Weed Guide—Lady’s-thumb.





Biocontrol: None.

Mechanical: Hand-hoeing or harrowing can kill youngplants. Repeated cultivation will stop emerging plantsfrom setting seed and will eventually exhaust the seedbank. Frequent mowing in pastures and meadows willprevent seed-set.

Fire: Not known to control lady’s-thumb.

Herbicides: There are many herbicides registered forcontrol, depending on crop. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Use clean, high-quality seed.Clean vehicles and equipment before leaving aninfested area. Keep forage crops and pastures in acompetitive state. Minimize disturbance to riparian

areas where control options are limited. Monitor theseareas and remove new outbreaks by hand-pulling.


95

Integrated Management SummaryEarly detection is important because this planthas a limited distribution in BC. Hand-pullplants and remove plant material from the sitebefore a seed bank can establish. Applyappropriate herbicides on new infestations toprevent seed-set and dispersal. Seed disturbedareas to perennial grasses and forbs to providecover and competition against lady’s-thumb.Manage grazing animals to maintain perennialplant communities.

Management ________________________________________

References __________________________________________


Flower: Theinflorescences are dense

clusters found at the stem tips orin the leaf axils. Theinconspicuous flowers are smalland greenish and lack petals.Flowering time is May throughSeptember.

Seeds/Fruit: Black, shiny, flattenedseeds are surrounded by a paperyenvelope, 1.0–1.5 mm broad(Douglas et al. 1998).

Leaves: Leaves can vary fromnarrow with entire margins towedge-shaped with toothed or lobedmargins (BC Ministry of Agricultureand Fisheries 1987). The somewhatsucculent leaves are alternate,stalked, and 3–10 cm long. The leafundersides are pale or purplish incolour with fine, greyish mealyparticles that can be rubbed off.

Stems: Each plant has a single, much-branched stemthat can grow 0.2–2.0 m tall. The grooved stems arebluish and become blotched with red or purplewith age.

Roots: Short, much-branched taproot.

Seedling: The cotyledons are up to 15 mmlong and are rounded and fleshy and havepinkish undersides. The first leaves areopposite and egg-shaped, but later leaves arealternate (Royer and Dickinson 1999).

Similar SpeciesExotics: Oak-leaved goosefoot(Chenopodium glaucum) has a prostrate orspreading growth form and has smallerleaves (1–3 cm long).

Natives: Leaves of maple-leaved goosefoot(Chenopodium hybridum) are thinner andresemble maple leaves. Various species of orache(Atriplex sp.) resemble the Chenopodiums but can bedistinguished by having at least some pairs of oppositeleaves.

Agricultural: One of the most abundant weeds ofagronomic, horticultural, and vegetable crops. Its tallstature and high water consumption allow it to out-compete crops and seriously reduce yield. It ispalatable to livestock when young, but, under veryfertile conditions, it can cause nitrate poisoning tosheep and swine.

Ecological: This weed invades disturbed habitats suchas roadsides and abandoned fields and is common onlogged-over lands, especially on burned slash-piles. Itdoes not usually invade native plant communities.

Human: Airborne pollen causes hay fever. Leaves,shoots, and seeds are consumed by humans. An extractof the leaves is used to treat internal parasites.

LAMB’S-QUARTERS

Chenopodium album L.Family: Chenopodiaceae (Goosefoot).

Other Scientific Names: Chenopodium strictum spp.glaucophyllum.

Other Common Names: Pigweed.



96

Impacts ____________________________________________


General requirements: The plant tolerates a widerange of environmental conditions but requires sunlightand well-drained soils. It is often associated with sandyor gravelly soils, such as a gravel pit. It is mostabundant on cultivated, calcareous soils. In BC, it isfound in cultivated crops, gardens, fields, roadsides,and disturbed places.

Distribution: Common in all agricultural reportingregions of the province and found throughout Canadaand the US.


Life cycle: Lamb’s-quarters is a summer annual. Seedsoverwinter under the soil, then germinate, flower, andset seed before killing frost in the autumn. Seedlingscan emerge from May until September, and floweringcan occur from May to October. Both dormant and

non-dormant seeds are produced and more dormantseeds are produced early in the season when the daysare long. Seeds are more likely to remain dormantunder drought or shaded conditions (Bassett andCrompton 1978).


Seed production: About 72,000 seeds are produced onan average-sized plant.

Seed bank: Seeds can remain viable in the seed bankfor nearly 40 years,

Dispersal: Most seeds drop beside the parent plants.Birds and livestock consume and spread the seeds.Agricultural practices, road building, and movinggravels and ballast also disperse seeds.

Hybridization: No evidence of hybridization.

Bassett, I. J., and C. W. Crompton. 1978. The biologyof Canadian weeds. 32. Chenopodium album L.Canadian Journal of Plant Science 58: 1061–1072.

BC Ministry of Agriculture and Fisheries. 1987. WeedSeries Fact Sheet—Lamb’s-quarters.

Douglas, G. W., G. B. Straley, D. Meidinger, and J.Pojar. 1998. Illustrated Flora of British Columbia.

Vol. 2: Gymnosperms and Dicotyledons(Balsaminaceae through Cuscutaceae).Province of British Columbia.

Royer, F., and R. Dickinson. 1999.Weeds of Canada and the Northern United States.Edmonton: University of Alberta Press.

Biocontrol: None, although many insects,microorganisms, and viruses attack lamb’s-quarters.

Mechanical: This weed is highly susceptible to cuttingor trampling, especially during early stages of growth(Bassett and Crompton 1978). Mowing can be effectiveif applied before plants flower. Emergence is notreduced by initial tillage in the spring because thisspecies germinates throughout the growing season.Repeated tillage is required to destroy seedlings,prevent seed-set, and deplete the seed bank.

Fire: Fire does not affect the large seed bank.

Herbicides: Lamb’s-quarters is susceptible to manycommonly used herbicides. Some populations of theweed are resistant to the triazine group of herbicides(e.g., atrazine). Herbicides are most effective duringearly growth stages. Consult the most recent edition ofBC Ministry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: In natural areas, minimizedisturbance, graze native plants moderately, and seeddisturbed areas to perennial grasses to maintaincompetitive forage growth. Grazing the weed,especially early in the season, will prevent seedproduction and crop-yield losses (note caution re:potential for nitrate toxicity of young, fertile plants).


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Management ________________________________________

References __________________________________________

Integrated Management SummaryLamb’s-quarters requires disturbed, openhabitats to grow. Maintaining vigorousperennial stands will prevent establishment.The plant can be managed with mowing,grazing, or herbicides.


Flower: Flowers are yellowish green, small,arranged in numerous small clusters with

distinctive pairedbracts underneath.Bracts are heartshaped and yellow-green.

Seeds/Fruit: Seeds areoblong, greyish to purple,contained in a 3-celledcapsule.

Leaves: Leaves are alternate,narrow, 2–6 cm long.

Stems: Mature plants are 20–90cm tall. Stems are thickly clustered.

Roots: Extensive lateral root system.

Seedling: Seed leaves (cotyledons) arelinear to lanceolate, with entire margins.

Other: The entire plant containswhite, milky latex. Foliage of theplant is smooth and hairless.

Similar Species

Exotics: Six species of spurgeoccur in BC, all introduced(Douglas et al. 1999).

Natives: None.

Agricultural: Invades rangeland and reduces itsproductivity for livestock and wildlife (Lajeunesse etal. 1999).

Ecological: Leafy spurge is a long-lived perennial thatreproduces by seeds and buds on persistent, creepingroots (Powell et al. 1994). All parts of the plant containa milky latex that is poisonous to some livestock. The

plant produces an allelopathic compound that inhibitsthe growth of other plants (Butterfield et al. 1996).

Human: The milky latex can cause irritation,blotching, blisters, and swelling. Wear gloves whilepulling or contacting this plant. Never rub the eyes orface until after the hands are thoroughly washed.

LEAFY SPURGE

Euphorbia esula L. Family: Euphorbiaceae (Spurge).

Other Scientific Names: Euphorbia virgata.




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Habitat and Ecology __________________________________General requirements: In BC, grows at low- to mid-elevations on dry roadsides, fields, grasslands, openforests, and disturbed habitats. Leafy spurge has a widerange of ecological tolerances from very dry to verywet but appears best adapted to semi-arid areas(Butterfield et al. 1996). It grows on a range of soiltypes but is most abundant in coarse-textured soils andleast abundant on clayey soils (Butterfield et al. 1996).

Distribution: Isolated pockets occur in the Thompson,Cariboo, Boundary, East Kootenay, Nechako, andNorth Okanagan areas (Powell et al. 1994). It isconsidered a major concern in the Kootenay,Okanagan, Thompson, Cariboo, and Ominecaagricultural reporting regions. It is widespreadthroughout Canada and the western US.



Impacts ____________________________________________

Life cycle: Emerges in the spring and develops flowerswithin 1–2 weeks after stem elongation (Butterfield etal. 1996). Flower clusters have 8–16 branches.Flowering generally ends in late June to mid-July,depending on geographic location. Three seeds areproduced per cluster (Powell et al. 1994). Seeds matureabout 30 days following pollination.

Mode of reproduction: By seed but primarily fromlateral roots. Roots can extend nearly 4.5 m laterallyand about 9 m deep, with up to 300 buds forming onthe roots (Butterfield et al. 1996).

Seed production: A large plant may produce up to130,000 seeds (Rutledge and McLendon. Undated).

Seed bank: Seeds can remain viable in the soil 5–8years, although most seeds will germinate in the first 2years (Butterfield et al. 1996).

Dispersal: Mature seeds can be dispersed up to 4.5 mfrom the parent plant. Seeds float on water and can betransported by animals and remain in flooded seedbanks.


Beck, K. G. 1996. Leafy spurge. Colorado StateUniversity Cooperative Extension Natural ResourceSeries, No. 3. 107.http://www.colostate.edu/Depts/CoopExt/PUBS/NATRES/03107.html [24 Jan 00].

Beck, K. G., and L. R. Rittenhouse. 2000. Managingleafy spurge with sheep grazing and flea beetles.Proceedings of the Western Society of Weed Science. Inpress.

Best, K. F., G. G. Bowes, A. G. Thomas, and M. G.Maw. 1980. The biology of Canadian weeds. 39.Euphorbia esula L. Canadian Journal of Plant Science60: 651–663.

Biesboer, D. D. 1998. Element stewardship abstract forEuphorbia esula. The Nature Conservancy, WildlandWeeds Management and Research Program.http://tncweeds.ucdavis.edu/esadocs/euphesul.html [28Jul 98].

Biocontrol: Seven biocontrol agents have beenreleased in the province: Aphthona nigriscutis, A.cyparissiae, A. czwalinae, A. lacertosa, A. flava (flea-beetles), Hyles euphorbiae (moth), and Lobesiaeuphorbiana (moth). Thus far, Apthona nigriscutis hashad the most significant impact, although otherApthona species have been successful in selectedhabitats. Sheep-grazing has been successfully used tomanage spurge on ranches in Montana: once the sheepwere removed, the spurge would quickly return(Biesboer 1998). There are likely few opportunities forthis kind of management in BC.

Mechanical: Tillage, mowing, and pulling aregenerally ineffective control treatments because of theplant’s extensive root system.

Fire: Burning alone is unlikely to provide adequatecontrol because of the extensive root system.

Herbicides: Picloram has been used successfully onsmall infestations (Lajeunesse et al. 1999). Springapplications of a combination of picloram and 2,4-Dalso were effective when the herbicide was appliedbefore flowers emerged (Beck 1996). Similarly, annualapplications of dicamba and 2,4-D in combination havealso provided good management (Beck 1996). Beck(1996) found that applications of glyphosate wereeffective when applied at one-month intervals and

followed by autumn grass seeding. Consult the mostrecent edition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Cultural methods such as hand-pulling, mowing, and cutting are not likely to havemuch success in controlling leafy spurge. Protectdisturbed areas by seeding to perennial grasses. Ensurethat grazing maintains vigorous perennial plantcommunities.


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Integrated Management Summary Integrated management will require acombination of prevention, biocontrol,chemical control, and seeding disturbed areasto perennial grasses. Where infestations arelarge, the only likely long-term managementstrategy will be biocontrol, at least initially.Seeding and good land management practicesmust follow.

Management ________________________________________

References __________________________________________


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Butterfield, C., J. Stubbendieck, and J. Stumpf. 1996.Species abstracts of highly disruptive exotic plants.Jamestown, ND: Northern Prairie Wildlife ResearchCenter Home Page.http://www.npwrc.usgs.gov/resource/othrdata/exoticab/exoticab.htm [16 Jul 97].

Douglas, G. W., D. Meidinger, and J. Pojar, eds. 1999.Illustrated Flora of British Columbia. Vol. 3:Dicotyledons (Diapensiaceae through Onagraceae).Province of British Columbia.

Lajeunesse, S., R. L. Sheley, R. Lym, D. Cooksey, C.Duncan, J. Lacy, N. Rees, and M. Ferrell. 1994. Leafyspurge: biology, ecology and management. ExtensionBulletin EB 34. Bozeman: Montana State University.

Lajeunesse, S., R. L. Sheley, R. Lym, and C. Duncan.1999. Leafy spurge. In R. L. Sheley and J. K. Petroff,eds. Biology and Management of Noxious RangelandWeeds. Corvallis: Oregon State University Press.

Lym, R. G. 1998. The biology and management ofleafy spurge (Euphorbia esula) on North Dakotarangeland. Weed Technology 12: 367–373.



Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Leafy spurge. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.


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Flower: Compactclusters of purple

flowers form at the tip ofthe stems. Bracts at thebase of the flowers aresticky and tipped with along spine.

Seeds/Fruit: Seeds arestraw-coloured, 2.5–3.5 mmlong, with a 9–10 mm longtawny pappus (Douglas etal. 1998).

Leaves: Spiny basal and stemleaves are deeply segmented withprominent woody veins (Cranstonet al. 2000). Leaves are lightly todensely hairy on the undersides andhave winged bases.

Stems: Slender, erect stems are usually unbranchedand grow 0.3–2.0 m tall. Stems have spiny wingsarising from the winged leaf-bases.

Roots: Fibrous.


Similar Species

Exotics: The prominent spiny wings of thestems separate marsh plume thistle frommost thistles (Cirsium sp.). Bull thistle(Cirsium vulgare) is a stout, branchedbiennial whose leaves bear stout, longspines at the tip of the lobes.

Natives: No native species have stemswith spiny wings.

Agricultural: Does not invade cultivated areas but canspread in moist pastures. This unpalatable plantreplaces desirable forage plants, thereby reducingcarrying capacity.

Ecological: Can colonize undisturbed riparian habitats,moist fields, and meadows, where it may replace native

vegetation, reducing wildlife and livestock foragevalues. Colonizes cut-blocks after harvesting and formsdense stands that compete with tree seedlings. Tall,persistent stems can cause snow press and other formsof mechanical injury to tree seedlings.


MARSH PLUME THISTLE

Cirsium palustre (L.) Scop.Family: Asteraceae (Sunflower)


Other Common Names: Marsh thistle.

Legal Status: Regional Noxious: Bulkley-Nechako, Fraser-FortGeorge.


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Impacts ____________________________________________



General requirements: Well adapted to moist-to-wetopenings, including pastures, bog and fen communities,cut-blocks, and roadsides. Grows in a range of soiltypes, including forest floor and even gravel, providedseepage is present. Although generally shade-intolerant,it will germinate under the forest canopy.

Distribution: Present in the Cariboo, VancouverIsland, and Omineca agricultural regions. Mostcommon in the Robson Valley between McBride andPrince George.


Life cycle: A biennial that germinates in the first year,

overwinters as a rosette, then sets seed and dies thefollowing year.




Dispersal: Wind and water disperse the light,parachute-like pappus. Ingestion of seeds by birds mayalso disperse seeds.




Biocontrol: No specific agents available. A seed-eatingweevil (Rhinocyllus conicus) has successfullyestablished on marsh plume thistle in the RobsonValley Forest District and experimental trials arecurrently underway.

Mechanical: In areas that are suitable for use ofmowing equipment, mowing before flowering willprevent seed-set.

Fire: Effect not known.

Herbicides: Research is required to develop aherbicide prescription for this species.

Cultural/Preventive: On small infestations, hand-pullseedlings, rosettes, and mature plants before they setseed.


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Management ________________________________________

References __________________________________________

Integrated Management SummaryLearn to identify this weed. Early detection isimportant to limit establishment of matureplants, seed banks, and large infestations. Onsmall infestations, hand-pull seedlings,rosettes, and mature plants before they setseed. Where practical, seed disturbed areas toperennial grasses and forbs to provide coverand competition against this weed.


Flower: Several to many large pink topurplish red (occasionally white) heads are

borne at the end of branches. The bracts are light todark brown with a tattered fringe or comb at the tips(Douglas et al. 1998).

Seeds/Fruit: Seeds are2–3 mm long. A tuft(pappus) ofpapery bristles4–5 mm longmay be presentor lacking.

Leaves: Thelance-shapedbasal leavesare sparselycovered inlong hairs andmay bepinnately cut orhave wavymargins. They soonwither. The lowerstem leaves have longstalks and are entire or

may be shallowly lobed; the upper stem leaves aresmall, stalkless, and unlobed.

Stems: Stems are erect, branched, andthinly covered in hairs. Plants grow0.4–1.0 m tall.

Roots: Taproot with a woody crown.


Similar Species

Exotics: Resembles many of theknapweeds, but meadow knapweed, blackknapweed (Centaurea nigra), and brownknapweed (Centaurea jacea) are distinguished by theirundivided leaves. Meadow knapweed may be a hybridof brown and black knapweed, so it is difficult todistinguish the 3 species (Frankton and Mulligan1970). Black knapweed has a well-developed pappus,long stalks on the lower stem leaves, and a narrowfringe on the involucral bracts. Brown knapweed hasno pappus and has short stalks on the lower leaves anda narrow fringe on the involucral bracts. Meadowknapweed has a weakly developed to absent pappus,long stalks on the lower stem leaves, and wide, bushyfringes on the involucral bracts.

Natives: None.

Agricultural: Can invade rangeland and pastures,causing reduction in carrying capacity. It can also resultin reduced yields in hayfields.

Ecological: Not known to establish in undisturbednatural plant communities. Typically, it grows on

roadsides and disturbed areas, where it forms densestands that hinder re-establishment of desirable nativespecies.

Human: None.

MEADOW KNAPWEED

Centaurea debauxii Gren. & Godr.Family: Asteraceae (Sunflower).

Other Scientific Names: Centaurea debauxii.


Legal Status: Regional Noxious: Columbia-Shuswap.


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Impacts ____________________________________________


General requirements: Infests roadsides, fields,pastures, and disturbed habitats at low- to mid-elevations.

Distribution: Considered a major concern in theOkanagan agricultural reporting region and present inmost areas of BC except for the Peace River, Cariboo,and Lower Mainland regions. It is common in Oregonand northern California.


Life cycle: Perennial. Seeds can germinate from springthrough autumn, with autumn-germinated plantsusually overwintering as a rosette. Plants flower fromJuly through August, depending on geographiclocation.


Seed production: No information is available. Blackknapweed, a close relative, can produce more than1,000 seeds/plant.

Seed bank: Seeds can remain viable in the soil forseveral years.

Dispersal: Most seeds are dispersed beside the plant.Can be dispersed by birds, which eat the seeds, or bywind.

Hybridization: Considered a hybrid of black andbrown knapweed.

Douglas, G. W., G. B. Straley, D. Meidinger, and J.Pojar. 1998. Illustrated Flora of British Columbia: Vol.1: Gymnosperms and Dicotyledons (Aceraceae throughAsteraceae). Province of British Columbia.


Biocontrol: Urophora affinis (fly) and Urophoraquadrifasciata (fly), 2 seed head flies released tomanage diffuse and spotted knapweed, can use thisspecies as a host plant. Although they may reduce seedproduction, these agents alone cannot manage thisweed.

Mechanical: Larger infestations can be mowed toremove topgrowth, then new seedlings treated withherbicide as they emerge. Bag and burn mown plants.

Fire: Fire can destroy seeds on standing seed heads,but it will not kill seeds in the seed bank. Herbicidesare required to control emerging seedlings followingburning.

Herbicides: Picloram, dicamba, or a combination ofclopyralid and 2,4-D have all been effective. Consultthe most recent edition of BC Ministry of Agriculture,Food and Fisheries Crop Production Guides forspecific recommendations. Before applying


Cultural/Preventive: Small infestations can be hand-pulled. Minimize disturbance and manage for vigorouspastures dominated with perennial plants or naturalcommunities.


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Management ________________________________________

References __________________________________________

Integrated Management SummaryControl new infestations immediately.Disturbed areas such as roadsides, feedingareas, corrals, trails, and stream banks shouldbe monitored for new infestations andcontrolled. Seed disturbed areas with perennialgrasses and forbs.


Flower: The white topinkish flowers are

fragrant, arranged in smallclusters, and open only atnight. The flowers have 5notched petals, 20–35 mm long.The sepals are fused together toform a tubular calyx surrounding theflower. The calyx has 5 teeth at the tipand 10 prominent nerves and is coveredin sticky hairs.

Seeds/Fruit: The pale, smooth capsulesare egg-shaped, 1.5–2.5 cm long withtiny, rough, brown to greyish black seeds.

Leaves: Basal leaves are spoon-shaped,5–12 cm long, on short stalks. Theopposite stem leaves have no stalk, and arelance-shaped, 2–10 cm long, and coveredin slightly sticky stiff hairs on both sides.

Stems: The several stems are erect andbranched, 20–90 cm tall. Stems areswollen at the nodes and hairy, withthe hairs becoming sticky near the top.

Roots: Taproot.

Seedling: A leaf rosette is formedafter the seedling leaves (cotyledons)have emerged.

Similar Species

Exotics: White cockle (Lychnis alba) isperennial and lacks the sticky hairs on theupper part of the plant. The white cockle producesseparate male and female flowers, while the catchflyhas both sexes in the same flower.

Natives: A number of Silene are native to the province,and several are rare. While all Silene share the tubularflower and inflated calyx, the native species are nearlyall perennial and none have the stickiness of night-flowering catchfly.

Agricultural: Infests grain fields, legume crops, andpastures and can be a problem in gardens andhorticultural nurseries. It sometimes contaminatesclover and forage seed, making it difficult to clean.Livestock find it unpalatable, whether in pasture orcured in hay (BC Ministry of Agriculture and Food1984).

Ecological: Grows on roadsides, railroads, fields, anddisturbed habitats, where it usually remains a minorcomponent. Its prolific seed production enables it tocolonize disturbed sites rapidly.

Human: None known.

NIGHT-FLOWERING CATCHFLY

Silene noctiflora L.Family: Caryophyllaceae (Pink).

Other Scientific Names: Melandrium noctiflorum.

Other Common Names: Sticky cockle, night-flowering campion.



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Impacts ____________________________________________



General requirements: In BC, grows in fields,disturbed areas, and roadsides at low- to mid-elevations.It requires high summer temperatures for germinationand usually grows on sandy or gravelly soils.

Distribution: Found in all agricultural reporting regionsin the province and considered a major concern in thePeace River region. It is found in all provinces (but isuncommon in Newfoundland and the Maritimes) andthroughout the northern US (McNeill 1980).

Historical: Introduced from Europe. This plant wasknown in Canada by the 1860s.

Life cycle: An annual or winter annual, night-flowering catchfly overwinters as seed or as leafyrosettes if there is protective snow cover. In spring, thestems rapidly elongate, and flowering begins by mid-June, with some plants not coming into flower untilSeptember. Seed ripens about a month after floweringstarts. Some seeds germinate in the autumn but mostremain dormant over winter.


Seed production: A single plant can produce over2,500 seeds.

Seed bank: Seeds are very viable, especially after anafter-ripening period of 3–6 months. Seeds remainviable longer than 3 years in cultivated soil.

Dispersal: Most seeds fall to the ground from theparent plant. Seeds are very similar to those of cropclovers and are difficult to separate, so seed impuritieshave been an important source of dispersal. Ingestedseeds survive passage through the digestive system oflivestock.


BC Ministry of Agriculture and Food. 1984. Night-flowering catchfly. Agdex 640 Fact Sheet.


McNeill, J. 1980. The biology of Canadian weeds. 46.Silene noctiflora L. Canadian Journal of Plant Science60: 1243–1253.

Biocontrol: None.

Mechanical: Shallow cultivation can create sufficientdisturbance to population density of this plant.

Fire: In Britain, stubble burning and early tillage hasdecreased density, but this weed flowers much later inBritain than in BC.

Herbicides: Resistant or somewhat resistant to severalcommon herbicides, including 2,4-D, MCPA, fenoprop,and mecoprop (McNeill 1980). EPTC and trifluralinare effective when used before planting, whilebromoxynil and MCPB are effective post-emergence.More consistent management is often achieved withcombinations of 2 or more herbicides. Consult the mostrecent edition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Improved separation of cropseed has reduced the spread of night-floweringcatchfly.


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Management ________________________________________

References __________________________________________

Integrated Management SummaryOnce established, night-flowering catchfly ismost effectively managed with herbicides.Small infestations can be hand-pulled.Minimize disturbance and seed disturbed areasto perennial grasses and forbs. Managegrazing animals to maintain perennial plantcommunities.

Growth form:Biennial forb.

Flower: Flowerheads are terminal, solitary,2.5–5.0 cm in diameter,nodding. Flowers are deep reddishpurple. Flower head bracts end insharp, spiny tips.

Seeds/Fruit: One-seeded, egg-shaped fruit (achene) about 5mm long, shiny, yellowishbrown, with a plume (pappus) ofwhite hair-like bristles.

Leaves: Stem leaves arealternate, dark green, deeplylobed or pinnately cut, and spinymargined. The leaf margins areoften white. The leaves extendonto the stem, giving a wingedappearance (Whitson et al. 1996).

Stems: The smooth, non-spiny stems grow 0.3–2.4 mtall (Douglas et al. 1998). It can appear as asolitary stem or with several highlybranched stems from one base.

Roots: Fleshy taproot.


Similar Species

Exotics: Similar to plumeless thistle (Carduusacanthoides). Rosettes of plumeless thistle aredistinguished from those of nodding thistle by havingleaves that are deeply serrate (saw-toothed) almost tothe midrib.

Natives: There are many native thistle species (in thegenus Cirsium). The natives generally do nothave leaves clasping the stem all the wayfrom node to node (strongly decurrentleaves). Many have hairy upper andlower leaf surfaces and are blue-green orgrey in colour.

Agricultural: Reduces pasture production and isunpalatable to livestock.

Ecological: A highly competitive weed that invadespasture, rangeland, forestland, cropland, and disturbedareas, where it spreads rapidly and forms extensive

stands (Rutledge and McLendon. Undated). Noddingthistle may produce allelopathic chemicals that inhibitdesirable plants beyond the spread of the rosettes(Wardle et al. 1993).


NODDING THISTLE

Carduus nutans L. spp. leiophyllis(Petrovic) Stoj. & Stef.Family: Asteraceae (Sunflower).


Other Common Names: Musk thistle, nodding plumeless thistle.



108



General requirements: Found along dry roadsides anddisturbed habitats at mid-elevations. Nodding thistledoes not appear to have any specific climaticrequirements other than a cool period before flowering(Butterfield et al. 1996). It occurs in areas with as littleas 25 cm of annual precipitation and establishes best in

bare soil (FEIS 1996). Nodding thistle grows on all soiltextures, but the soils must be well-drained and have apH range of 6.0–8.9 (Butterfield et al. 1996).

Distribution: Found throughout North America.Nodding thistle occurs in isolated pockets in theChilcotin, Thompson, Nicola, Kootenay, Okanagan,

Impacts ____________________________________________

Similkameen, Boundary, and Bulkley Valley areas ofBC (Powell et al. 1994; Douglas et al. 1998).

Historical: Introduced from Eurasia or North Africa.

Life cycle: Seeds germinate in the autumn, forming arosette of leaves. Typically, nodding thistle overwintersas a rosette and bolts the following spring betweenApril and June. Flowering begins in late May or earlyJune and continues through mid-July (Butterfield et al.1996). Seeds mature and are dispersed 1–3 weeks afterflowering. Seedlings establish only on bare soils anddo not establish well under shaded conditions (Beck1999).


Seed production: Average productivity isapproximately 10,000 seeds/plant, but a single plantcan produce up to 100,000 seeds (Beck 1999).

Seed bank: Seeds can remain viable for at least 10years.

Dispersal: By wind, water, wildlife, and livestock(Beck 1999).

Hybridization: May hybridize with plumeless thistle(Carduus acanthoides).

Biocontrol: Rhinocyllus conicus (weevil),Trichosirocalus horridus (weevil), and Urophorasolstitialis (fly) have been released in BC (Powell et al.1994). Adult Rhinocyllus feed on the leaves in spring,mate, and deposit eggs on the bracts (Butterfield et al.1996). When the eggs hatch, the larvae begin to boreinto the flower head, reducing the ability of the plantsto produce viable seed. In some cases the weevil hasreduced nodding thistle populations to less than 10% ofpre-release levels (Rutledge and McLendon. Undated).This weevil is not entirely host-specific, however, andwill complete its life cycle on native thistles (Louda etal. 1997).

Mechanical: Repeated mowing, hand-pulling, orcutting can be used to stop the spread of noddingthistle. Mowing or hand-cutting after flowering, butbefore seed-set, prevents seed development anddispersal (Heidel 1987). When pulling nodding thistle,it is important to completely remove the crown so thatthe plant does not simply re-bolt and produce seeds.Repeated visits at weekly intervals over the 4–7-weekflowering period are necessary because not all plantsflower at the same time (Heidel 1987). Cut plantsshould be deeply buried or burned because seeds canmature and become viable after cutting (Rutledge andMcLendon. Undated).


Herbicides: Nodding thistle is usually controlled withherbicides. Chemical control is most effective at therosette stage, and quickly decreases once the plant hasbolted (Butterfield et al. 1996). Clopyralid, 2,4-D, anddicamba are all effective before the plant bolts. A

combination of 2,4-D and dicamba provided 97%control in an experiment in Minnesota (Butterfield etal. 1996). Butterfield et al. (1996) found that a autumnapplication of picloram to rosettes, when other plantswere dormant, was effective and had less impact onnon-target species. Metsulfuron is effective on boltedplants (Beck 1999). Consult the most recent edition ofBC Ministry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Prevent the establishment of newinfestations by minimizing disturbance and seeddispersal, eliminating seed production, and maintainingvigorous native communities.


109

Management ________________________________________

Integrated Management SummaryThe key to managing nodding thistle is toprevent seed production. Dense nodding thistlestands can be spot-treated with herbicides or bypulling or cutting (Rutledge and McLendon.Undated). Control methods may have to berepeated for many years to completelyeliminate a stand because seeds can remain inthe seed bank for up to 10 years. Mostinfestations in BC are so severely stressed byinsect agents that other methods of control areseldom required.


110

Beck, K. G. 1999. Biennial thistles. In R. L. Sheley andJ. K. Petroff, eds. Biology and Management of NoxiousRangeland Weeds. Corvallis: Oregon State UniversityPress.

Butterfield, C., J. Stubbendieck, and J. Stumpf. 1996.Species abstracts of highly disruptive exotic plants.Jamestown, ND: Northern Prairie Wildlife ResearchCenter Home Page.http://www.npwrc.usgs.gov/resource/othrdata/exoticab/exoticab.html [16 Jul 97].

Desrochers, A. M., J. F. Bain, and S. I. Warwick. 1988.The biology of Canadian weeds. Carduus nutans L.and Carduus acanthoides L. Canadian Journal of PlantScience 68: 1053–1068.


FEIS—Fire Effects Information System. 1996.Prescribed Fire and Fire Effects Research Work Unit,Rocky Mountain Research Station (producer). USForest Service. http://www.fs.fed.us/database/feis/ [12Mar 98].

Heidel, B. 1987. Element stewardship abstract forCarduus nutans, musk thistle. The Nature Conservancy,Wildland Weeds Management and Research Program.http://tncweeds.ucdavis.edu/esadocs/documnts/cardnut.html [30 Jul 98].

Louda, S. M., D. Kendall, J. Connor, and D.Simberloff. 1997. Ecological effects of an insectintroduced for the biological control of weeds. Science277: 1088–1090.


Rutledge, C. R., and T. McLendon. Undated. Anassessment of exotic plant species of Rocky MountainNational Parks. Department of Rangeland EcosystemScience, Colorado State University. Northern PrairieWildlife Research Center Home Page.http://www.npwrc.usgs.gov/resource/othrdata/Explant/explant.htm [15 Dec 98].

Wardle, D. A., K. S. Nicholson, and A. Rahman. 1993.Influence of plant age on the allelopathic potential ofnodding thistle (Carduus nutans) against pasturegrasses and legumes. Weed Research 33: 69–78.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Musk thistle. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

References __________________________________________


111


Growth form:Perennial forb.

Flower:Flowering heads areclustered at the top of theleafless stems and haveorange to red petal-like rayflowers with notched tips.

Seeds/Fruit: Achenes areabout 2 mm long, darkbrown or black,have ridges andbristly plumes.

Leaves: Leaves aremostly basal, spatulate-shaped, and covered withstiff hairs.

Stems: Stems are erect, usuallysolitary with stiff hairs (at the base)and 0.3–1.2 m tall (Douglas et al. 1998).

Roots: Fibrous root system with a woody stem base.Stolons root at nodes.

Seedling: Seedling leaves have bristly hairs.

Other: Plants contain milky juice.

Similar Species

Exotics: There are 14hawkweeds in BC, but onlyorange hawkweed has orangeflowers. All other native and exotichawkweeds have either white oryellow flowers. The yellowflowered hawkweed (Hieraciumpilosella) is similar but occurs onlyrarely in the south of the province.

Natives: See above.

Agricultural: Hawkweed is not normally competitivewith crop species in the US (Callihan et al. 1997); itsimpact on agricultural crops in BC is unknown.

Ecological: Although new populations of orangehawkweed likely originate from seeds, established

populations expand largely through vegetative growthby stolons. Patches can expand quickly, producingdense mats of rosettes (Callihan et al. 1997).


ORANGE HAWKWEED

Hieracium aurantiacum L.Family: Asteraceae (Sunflower).


Other Common Names: Orange-red king devil, devil’s paintbrush.

Legal Status: Regional Noxious: Bulkley-Nechako, Cariboo, CentralKootenay, Columbia-Shuswap, East Kootenay, Thompson-Nicola.


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Impacts ____________________________________________


General requirements: Orange hawkweed grows inthe province at low- to mid-elevations, usually on openareas such as pastures, meadows, clearings, roadsides,and disturbed sites. It appears best adapted to well-drained, coarse-textured soils (Wilson et al. 1997) thatare often acidic (Frankton and Mulligan 1970).

Distribution: Scattered and locally abundant in BCsouth of 55o N and is regarded as a major concern inthe Kootenay, Okanagan, Thompson, Cariboo,Omineca, and Peace River agricultural reportingregions. Orange hawkweed is established andspreading rapidly in northern Idaho, northeastern

Washington, and northwestern Montana (Wilson andCallihan 1999).


Life cycle: Perennial plants that form rosettes in springand early summer and spread primarily by stolons.Plants flower in June–July and quickly produce seed.Plants overwinter as rhizomes and regrow the nextspring (Wilson et al. 1997).

Mode of reproduction: By seed, stolons, and rhizomes.

Seed production: Flowering stem may produce severalhundred seeds.


Dispersal: Believed to be spread primarily byrecreationists, pack animals, and hay. Although seedsare plumed, they are not widely dispersed by wind(Wilson et al. 1997).


Callihan, R. H., L. M. Wilson, J. P. McCaffrey, T. W.Miller. 1997. Hawkweeds. Pacific Northwest ExtensionPublication 499. Cooperatively published by theUniversity of Idaho Cooperative Extension System,Oregon State University Extension Service,Washington State University Cooperative Extension,and the US Department of Agriculture.



Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Orange hawkweed. Weeds of the West. Western Societyof Weed Science, in cooperation with the WesternUnited States Land Grant Universities CooperativeExtension Services, Newark, CA.

Wilson, L. M., J. P. McCaffrey, P. C. Quimby, Jr., J. L.Birdsall. 1997. Hawkweeds in the northwestern UnitedStates. Rangelands 19: 18–23.

Wilson, L. M., and R. H. Callihan. 1999. Meadow andorange hawkweed. In R. L. Sheley and J. K. Petrokoff,eds. Biology and Management of Noxious RangelandWeeds. Corvallis: Oregon State University Press.

Biocontrol: None currently available. BC supports aninternational Hawkweed Biocontrol Consortiumcurrently researching the potential for biologicalcontrol.

Mechanical: Hand-pull small infestations but take carenot to scatter roots and stolons. Mowing prevents seedproduction but encourages increased vegetativereproduction.


Herbicides: Picloram and picloram plus 2,4-D provideexcellent control in BC when applied to activelygrowing plants in spring and early summer. Springapplications of dicamba are recommended for turf andlawns (Callihan et al. 1997). Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specific

recommendations. Before applying herbicides, readthe label for full use and precautionary instructions.



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References __________________________________________

Integrated Management SummaryIntegrated management strategies should focuson detecting and eradicating infestations asearly as possible and on implementing land usepractices that promote a continuous cover ofperennial vegetation.


Growth form: Short-lived perennial forb.

Flower: Flowering heads are solitary at theends of branches.

Flower heads have white rayflowers and yellow disk flowers.

Seeds/Fruit: Fruits arecylindrical and black and haveabout 10 ribs.

Leaves: Alternatelyarranged leaves becomeprogressively smallerupward along the stem.Basal and lower stemleaves are 4–15 cm long,lance-shaped to narrowly egg-shaped. The upper leavesbecome stalkless and toothed.

Stems: Mature plants are 20–80 cm tall witherect, smooth to sparsely hairy stems.

Roots: The plants have shallow, branchedrhizomes.


Similar Species

Exotics: Oxeye daisy is sometimes confusedwith the ornamental Shasta daisy (Chrysanthemummaximum), a more robust plant with largerflowers. Scentless chamomile (Matricariamaritima) and stinking chamomile(Anthemis cotula) also have whiteligulate flowers with yellow tubules(Frankton and Mulligan 1970).


Agricultural: The plant is unpalatable to cattle. Denseinfestations can reduce forage for livestock andwildlife. Oxeye daisy is of major concern as acontaminant in Peace River fine seed production.

Ecological: Oxeye daisy can become noxious and iscapable of dominating pastures and rangeland(Rutledge and McLendon. Undated).


OXEYE DAISY

Leucanthemum vulgare Lam. Family: Asteraceae (Sunflower).

Other Scientific Names: Chrysanthemum leucanthemum.

Other Common Names: White daisy.

Legal Status: Regional Noxious: Cariboo, North Okanagan, PeaceRiver, Thompson-Nicola.


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Impacts ____________________________________________


General requirements: Often grows along roadsidesand in fields and disturbed areas on moist tomoderately dry sites. It is often present on disturbedforest sites such as landing and skid trails in BC.

Distribution: Occurs at low- to mid-elevations ingrasslands and dry to moist forests. It is commonthroughout the province south of 56o N (Douglas et al.1998). It is widely distributed throughout Canada andthe US. This species is regarded as a major concern inthe Okanagan, Thompson, Cariboo, Omineca, and

Peace River agricultural reporting regions and ispresent in the Kootenay, Mainland, and VancouverIsland regions.


Life cycle: Rosettes must experience a period of coldtemperatures to initiate flowering (Rutledge andMcLendon. Undated). Flowering occurs from Junethrough August, depending on location. The plantgrows vigorously in nutrient-poor soils (Olson andWallander 1999).

Mode of reproduction: By seeds and vegetativelyfrom roots.

Seed production: Some plants produce over 500seeds.

Seed bank: Seeds can remain viable in the soil 2–3years or longer (Rutledge and McLendon. Undated).





Olson, B. E., and R. T. Wallander. 1999. Oxeye daisy.In R. L. Sheley and J. K. Petroff, eds. Biology andManagement of Noxious Rangeland Weeds. Corvallis:Oregon State University Press.

Rutledge, C. R., and T. McLendon. Undated. Anassessment of exotic plant species of Rocky

Mountain National Park. Department of RangelandEcosystem Science, Colorado State University.Northern Prairie Wildlife Research Center Home Page.http://www.npwrc.usgs.gov/resource/othrdata/Explant/explant.htm [15 Dec 98].

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Oxeye daisy. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: None.

Mechanical: Hand-pulling or digging before seedproduction. However, for this method to be successfulit is important to remove as much of the undergroundpart as possible.


Herbicides: Picloram, dicamba, 2,4-D, and glyphosateare effective herbicides. Consult the most recent editionof BC Ministry of Agriculture, Food and FisheriesCrop Production Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Prevent the establishment of newinfestations by minimizing disturbance and seed

dispersal, eliminating seed production, and maintaininghealthy native communities.


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References __________________________________________

Integrated Management SummaryIntegrated treatments should include acombination of nitrogen fertilization andherbicide treatment. Sheep or goats have beeneffective in selectively grazing oxeye daisywithout adversely affecting the desirablespecies, but this approach may not be practicalin most places where the plant grows in BC.


Growth form: Parasitic annual forb.

Flower: Tiny white orcream flowers, usually

clustered.

Seeds/Fruit: Seed pods arerounded capsules, containing1–4 tiny, rough seeds.

Leaves: No true leaves orgreen parts. Leaves arereduced to minute scales.

Stems: Slender, thread-likeyellow to orange twiningstems coil around forbs andshrubs. They adhere to hostplants with wart-likesuckers.

Roots: Minimal underground roots until the twiningstems contact a host plant, then aerial rootsand suckers are produced.

Seedling: Germinating stems produceslender stems without seed leaves(cotyledons).

Similar SpeciesExotics: Ten species of dodder havebeen found in Canada, all similar inappearance and effect (Frankton andMulligan 1970).

Natives: Several native dodders are present and areparasitic.

Agricultural: Dodders attack many vegetables, foragecrops (particularly alfalfa), and ornamentals. Dodderscan act as alternate hosts for some viral diseases ofvegetables. Legumes in particular are attacked by 3species in BC (C. approximata, C. epithymum, and C.pentagona). The twining stems also can get tangled inharvesting equipment.

Ecological: Dodders can parasitize many native plantsfrom herbs to shrubs. C. salina appears to have a closehost relation with plants of the goosefoot (particularlySalicaria) and sunflower family on saline sites in theFraser Valley, southern Vancouver Island, and the GulfIslands.


PARASITIC DODDER

Cuscuta spp.Family: Cuscutaceae (Dodder).

Other Scientific Names: Five species are present in BC: Cuscutaapproximata, C. cephalanthi, C. epithymum, C. pentagona, and C.salina.

Other Common Names: Strangleweed.



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General requirements: Dodders appear well adaptedto cultivated situations and succeed with many crops.

Distribution: Distributed across Canada and the US.Species are present in all agricultural reporting regionsof the province except the Omineca and Peace Riverregions. Most species are rare except for C. epithymumand C. salina (Douglas et al. 1998). Most are restrictedto low-elevation coastal areas, but C. approximata and

C. epithymum are found at mid-elevations in dryregions of the Interior.

Historical: C. pentagona and C. salina are nativespecies; all others were introduced from Eurasia.

Life cycle: Seeds germinate in the soil and produceslender stems. The stems have a short time to makecontact with a host plant before the seedling dies. Thedodder twines around the host plant and develops

Impacts ____________________________________________

suckers that penetrate the host, extracting food from it.The dodder loses contact with the soil. Stems of thedodder proliferate, sometimes forming dense mats, thenflowers and seed are produced (Frankton and Mulligan1970).


Seed production: Can produce over 16,000seeds/plant.

Seed bank: Seeds can remain dormant and viable inthe soil for over 60 years (BC Ministry of Agriculture,Food and Fisheries. Undated).

Dispersal: Seeds fall to the ground but can beharvested and transported with crops such as hay or onornamentals.


BC Ministry of Agriculture, Food and Fisheries. 2000.Weed Alert—Parasitic Dodder.



Biocontrol: None.

Mechanical: Infestations should be cut and burnedbefore seeds ripen. Tillage alone is not effective fordodder.

Fire: Burning dodder-infested material will destroy theplant and the seeds.

Herbicides: In alfalfa, chlorpropham should be appliedafter dodder has germinated but before it has attachedto the alfalfa plants. Glyphosate can effectively managedodder without harming alfalfa when applied at verylow rates soon after the dodder attaches (BC Ministryof Agriculture, Food and Fisheries 2000). Use of non-selective herbicides is often recommended for roadsideand non-crop infestations. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: New infestations should beimmediately burned or destroyed. Thoroughly clean

equipment, tools, and footwear before leaving infestedareas. Do not transport dodder-infested materials toother areas. Hay infested with dodder should not bebought or sold. Inspect new sources of hay on arrivaland watch stock and feeding areas for new infestations.If livestock have consumed infested hay, keep themcontained in one area until the seed has passed throughtheir digestive systems.


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References __________________________________________

Integrated Management SummaryUse a combination of cultural management andherbicides as required. Early detection isimportant and immediate management of newinfestations is essential.



Flower: White flowers are packed in denseclusters near the

ends of branches.

Seeds/Fruit: Fruitsare nearly round,about 2 mm indiameter, andusually sparselyhairy.

Leaves: Leaves arealternate, lance-shaped, entireto toothed, bright green to grey-green, and without clasping bases(whitetop leaves have claspingbases). The basal leaves are largerthan the upper leaves.

Stems: Mature plants are 0.5–2.0 m tall.

Roots: Perennial pepperweed roots grow deep into thesoil.


Other: The leaves and stem are covered with a waxylayer (Whitson et al. 1996).

Similar Species

Exotics: Whitetop (Cardariadraba) leaves have clasping bases;perennial pepperweed can also bedistinguished by its waxyappearance.

Natives: Many native members of thesunflower (Asteraceae) family resemblethis species in the rosette stage.

Agricultural: Invades irrigated pastures, cropland, andnative meadows (FEIS 1996).

Ecological: Aggressively colonizes riparian habitatsand can eliminate competing vegetation (FEIS 1996).


PERENNIAL PEPPERWEED

Lepidium latifolium L.Family: Brassicaceae (Mustard).


Other Common Names: Tall whitetop, broad-leaved peppergrass,Virginia pepperweed.

Legal Status: Regional Noxious: East Kootenay, Thompson-Nicola.


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Impacts ____________________________________________


General requirements: In BC, perennial pepperweed,although rare, grows on beaches and tidal shores, alongroadsides, in fields and disturbed habitats. Outside theprovince it is most often found in open, unshaded areason disturbed and often saline soils. Perennialpepperweed is locally common in riparian areas,marshy flood plains, valley bottoms, and seasonallywet areas from 1,675 to 2,750 m.

Distribution: Perennial pepperweed is known fromVancouver and Windermere (Douglas et al. 1998) and

also from Cranbrook (1997) and Walachin (1998). It isconsidered a major concern in the Kootenay andThompson agricultural reporting regions. This weed isfound throughout much of the western US.


Life cycle: Dense flower clusters appear in earlysummer and continue through August.


Seed production: Perennial pepperweed produces anabundance of highly germinable seeds. Seedproduction is from June to August.

Seed bank: Seeds have no apparent dormancy.

Dispersal: Seeds drop from the plant or travel shortdistances by wind and water.




Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Perennial pepperweed. Weeds of the West. WesternSociety of Weed Science, in cooperation with theWestern United States Land Grant UniversitiesCooperative Extension Services, Newark, CA.

Biocontrol: None.

Mechanical: Periodic mowing and spring burning havereduced perennial pepperweed density in Utah (FEIS1996).

Fire: (See above.)

Herbicides: Metsulfuron-methyl is the most effectiveherbicide in the US. Dicamba, glyphosate,chlorsulfuron, imazapyr, and a combination ofglyphosate and 2,4-D have also been effective in theUS. Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Cutting and pulling can managethis weed if plants are treated before seed-set.


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References __________________________________________

Integrated Management SummaryCutting or pulling, combined with herbicideapplications, can provide effectivemanagement of perennial pepperweed. Plantsshould be cut or pulled during the flower budstage and herbicides applied to the recoveringstems before they set seed.


Flower: Small, yellow, dandelion-likeflower heads are grouped in loose clusters

up to 5 cm across. The clusters are borne on glandularstalks and the bracts of the flower headsare often covered with sticky hairs. Aplant may have up to 20 heads butusually only a few flower at thesame time. Flowers from Juneto September.

Seeds/Fruit: Seeds are2.5–3.5 mm long, darkbrown, and ribbed witha parachute-likepappus (Douglaset al. 1998).

Leaves: Leavesare alternate withweakly prickledmargins and variableshapes. Lower leavesare stalked, but upperleaves are stalkless andclasp the stem.

Stems: Mature plants are 0.4–2.0 m tall. The singlestems are erect and branched only near the top. Thestems exude a milky juice when cut.

Roots: Perennial sow thistle has a vigorous root systemwith a deep vertical root as well as fleshy, spreading,horizontal roots.

Seedling: The first leaves are spatula-shaped and have irregular teeth thatpoint downward and have a prickle onthe tip (Royer and Dickinson 1999).

Similar SpeciesExotics: Perennial sow thistle differs from annual sowthistle (Sonchus oleraceus) by its extensive creepingroots and larger flower heads. Prickly lettuce (Lactucaserriola) has smaller flowers, but its leaves are pricklyon the underside midrib (Frankton and Mulligan 1970).

Natives: Several native lettuces (Lactuca sp.) resembleperennial sow thistle, but they either lack the extensive,creeping root system, or, in the case of blue lettuce(Lactuca tatarica), the flowers are blue.

Agricultural: An aggressive, creeping weed that canseverely reduce yields in cultivated fields and grainfields. It is not easily managed with chemicals orcultivation (Alberta Environmental Centre 1983). Thisweed is an alternate host for several viral diseases.

Ecological: Sow thistle is able to invade both naturalhabitats and disturbed sites, where it competes for

light, nutrients, light, and space. It can establish andbecome a serious problem on marshes, ponds, andother riparian areas. Chemicals from the roots anddecaying residue from old growth inhibit seedgermination of other species.

Human: Sow thistles contain chemical compoundsused for industrial and pharmaceutical purposes.

PERENNIAL SOW THISTLE

Sonchus arvensis L.Family: Asteraceae (Sunflower).

Other Scientific Names: Sonchus uliginosus.

Other Common Names: Creeping sow thistle, field sow thistle,field milk thistle, gutweed, swine thistle, marsh sow thistle.



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Impacts ____________________________________________


General requirements: Adapted to a wide range ofenvironmental conditions but is most competitive intemperate climates with abundant moisture. Does beston sites in fertile, moist soils in full sunlight (Zollingerand Parker 1999). Grows on dry to moderately dryroadsides, disturbed areas, cultivated fields, andriparian areas.

Distribution: Present in all agricultural regions of BCand a major concern in the Peace River region. Itoccurs in all Canadian provinces and throughout thenorthern US and is especially troublesome in thePrairie provinces (Zollinger and Parker 1999).

Historical: Introduced from Europe, likely in seedcrops.

Life cycle: Perennial sow thistle spreads by creepinghorizontal roots and seed. The above-ground portion of

the plant dies over winter, and new shoots emerge frombuds on the roots in spring. Plants flower from July toSeptember, depending on geographic location. Seedsare dispersed in the autumn and can germinate tooverwinter as rosettes or germinate in spring.


Seed production: Seed production is highly variable,depending on weather conditions, and ranges from1,400 to 35,000 seeds/m2 (Zollinger and Parker 1999).

Seed bank: Seeds are relatively short-lived, withviability decreased by nearly half after 2 years.

Dispersal: Mainly by wind, but some birds feed on theseeds.


Biocontrol: Two insects have been approved forrelease in Canada, but neither are currently available inBC. Tephritis dilacerata (fly) attacks the seed heads,while Cystiphora sonchi forms galls on vegetative partsof the plant. Several pathogens are being tested inCanada and the US. Sow thistle is palatable to cattleand sheep, and heavy grazing can manage somepopulations.

Mechanical: Intensive cultivation (every 3–4 weeks)over a long period can kill sow thistle by exhaustingroot reserves, but intermittent tillage simply spreads theroots and increases distribution. Mowing prior toflowering can prevent seed production, but severalmowings are required because of perennial sowthistle’s long flowering period (Zollinger and Parker1999).


Herbicides: Sow thistles are relatively resistant toherbicides, and high rates are required to kill theextensive root system. Sub-lethal concentrations mayincrease root shoot growth (Zollinger and Parker1999). Clopyralid, dicamba, 2,4-D, picloram, andglyphosate have been effective when plants are at thepre-bud or bud stage. Glyphosate is non-selective andis used to prepare a seedbed for re-vegetation. Sowthistles have waxy leaves, so the spray solutions musthave good wetting ability. Consult the most recent

edition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: New populations can beprevented by hand-pulling or cultivation before theirextensive root systems establish. Seed disturbed areasto perennial grasses and forbs to provide ground coverand competition against this weed.


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Integrated Management SummaryPerennial sow thistle management oncultivated areas involves an integratedapproach of intensive cultivation, competitivecrops, selective herbicides, or a combination ofall 3. On rangeland and undisturbed areas,seedlings from new infestations can beremoved by hand-pulling or herbicides, whileestablished populations may be managed withintensive grazing or herbicides. Chemicalcontrol may not be possible on the riparianareas where this weed commonly occurs.


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Alberta Environmental Centre. 1983. Weeds of Alberta.Alberta Agriculture Agdex 640-4.


Vol. 1: Gymnosperms and Dicotyledons (Aceraceaethrough Asteraceae). Province of British Columbia.



Zolinger, R. K., and R. Parker. 1999. Sowthistles. In R.L. Sheley and J. K. Petroff, eds. Biology andManagement of Noxious Rangeland Weeds. Corvallis:Oregon State University Press.

References __________________________________________


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Growth form: Winter annual or biennialforb.

Flower: Flower heads are solitary at theends of branches or in clusters of 2–5. Flower bractsare narrowly lance-shaped and appear as sharp spines.Flowers are purplish-pink andclustered in heads that are2–5 cm in diameter.

Seeds/Fruit: One-seeded fruit (achene),capped by a ring ofbristles.

Leaves: Basal rosetteleaves are usually10–20 cm long withspiny lobes. Stemleaves alternate,stalkless, hairyunderneath, andblending into the stem.

Stems: Mature plants are 0.3–1.2 m tall and have astout, fleshy taproot. Stems are freely branched aboveand covered with leaf-like spines that extend up to theflowering heads (Whitson et al. 1996).

Roots: Thick, fleshy taproot.


Other: Closely related to musk or nodding thistle(Carduus nutans).

Similar Species

Exotics: Similar to musk/nodding thistle. Rosettes aredistinguished from those of nodding thistle by havingdeeply serrate (saw-toothed) leaves almost to themidrib.

Natives: Native thistles generally do not have leavesclasping the stem all the way from node to node(strongly decurrent leaves), and many have hairy upperand lower leaf surfaces and are blue-green or grey incolour.

Agricultural: Unpalatable to livestock; large or denseinfestations may reduce available forage.

Ecological: Does not typically pose a threat to high-quality natural areas, although it has been known toinvade native and restored grasslands despite the

presence of dense, native prairie vegetation (WisconsinDNR 1998). One of the most aggressive thistles due toits large seed production (Feldman 1997).


PLUMELESS THISTLE

Carduus acanthoides L.Family: Asteraceae (Sunflower).


Other Common Names: Bristly thistle, spiny plumeless thistle.

Legal Status: Regional Noxious: Central Kootenay.


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General requirements: Grows in pastures, fields,disturbed habitats, and logged-over areas and alongroadsides at mid-elevations.

Distribution: In BC occurs in isolated pockets in theCariboo, Kamloops, Kootenay, and Boundary areas(Powell et al. 1994). Especially problematic on the

Great Plains and in mesic pastures of the inter-mountain West of the US, it is a major concern in theKootenay and Omineca agricultural reporting regionsin the province and is also present in the Thompsonagricultural region.


Impacts ____________________________________________

Life cycle: Seedlings emerge from early spring to lateautumn and the length of time to flowering can varyfrom 4 to 22 months (Wisconsin DNR 1998). A singletaproot is formed and stem elongation occurs in earlyMay. Flowering begins in early June and lowerbranches continue to flower until mid-August(Wisconsin DNR 1998).


Seed production: A single plant can produce up to9,000 seeds.

Seed bank: Under favourable conditions, 90–95% ofseeds may germinate (Feldman 1997) and seeds canremain viable in the soil for up to 10 years (WisconsinDNR 1998).

Dispersal: Seeds are mainly dispersed by wind.

Hybridization: May hybridize with musk or noddingthistle (Carduus nutans).

Feldman, S. R. 1997. Biological control of plumelessthistle (Carduus acanthoides L.) in Argentina. WeedScience 45: 534–537.

Louda, S. M., D. Kendall, J. Connor, and D.Simberloff. 1997. Ecological effects of an insectintroduced for the biological control of weeds. Science277: 1088–1090.


Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Plumeless thistle. Weeds of the West. Western Societyof Weed Science, in cooperation with the WesternUnited States Land Grant Universities CooperativeExtension Services, Newark, CA.

Wisconsin Department of Natural Resources. 1998.Musk or nodding thistle (Carduus nutans), plumelessor bristly thistle (Carduus acanthoides), and bull thistle(Cirsium vulgare).http://www.dnr.state.wi.us/org/land/er/invasive/factsheets/thistles.htm [27 Jan 99].

Biocontrol: Rhinocyllus conicus (weevil) andTrichosirocalus horridus (rosette weevil) appear tolimit populations of plumeless and musk or noddingthistle (Powell et at. 1994), but they may also usenative thistles as an alternate host.

Mechanical: As with musk or nodding thistle,plumeless thistle flower heads can be cut and removedto eliminate seed production. Rosettes can also beremoved mechanically. This can be an effective controlmethod for relatively small infestations. However, itmust be repeated annually to exhaust the soil seedbank.


Herbicides: Picloram, dicamba, 2,4-D, and glyphosatehave all been used successfully to manage this species.Metsulfuron-methyl will also control plumeless thistle.Herbicides should be applied in the spring, 10–14 daysbefore bolting, or in the autumn to new rosettes.Metsulfuron-methyl should be applied to bolting

plants. Consult the most recent edition of BC Ministryof Agriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Reseed controlled areas withdesirable species.


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References __________________________________________

Integrated Management SummaryManagement of plumeless thistle is similar tothat of nodding thistle. Elimination of seedproduction is key. Rosettes can be pulled ordug out by hand prior to bolting, or treatedwith herbicide. Once plants have bolted, seedheads must be removed to prevent theproduction of viable seed.



Flower: White flowers are borne inumbrella-like clusters

supported by a stalk.

Seeds/Fruit: Light brown, ribbed,and concave.

Leaves: Generally alternate but may beopposite above (Stubbendieck et al.1995). Leaves are shiny, green, and finelydivided and have a strong musty odour.Leaflets are segmented on short stalks.

Stems: Mature plants grow 1.2–3.0 m tall.Stems are erect, extensively branched, andcovered with purple spots.

Roots: Taproot.

Seedling: Seedling leaves are fern-likein appearance.

Similar Species

Exotics: Similar to other exoticmembers of the parsley family, such aswild caraway (Carum carvi) and wildcarrot (Daucus carota). Spotted stemsare diagnostic.

Natives: Water hemlock (Cicutadouglasii), which is similar inappearance, lacks the distinctivespotted stems.

Agricultural: Poison hemlock crowds out desirableforage species and can poison livestock and humans.Sheep are less sensitive to it than cattle and horses(DiTomasso 1999).

Ecological: Although not an aggressive invader, poison

hemlock may gradually increase in native riparian andlowland communities.

Human: All parts of the plant are highly poisonous,and poison hemlock should be handled with care.

POISON HEMLOCK

Conium maculatum L.Family: Apiaceae (Parsley).


Other Common Names: Hemlock.



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Impacts ____________________________________________


General requirements: Poison hemlock is generallyfound on dry to moist soils, can tolerate poorly drainedsoils, and tends to be scattered in riparian areas. It isusually found along streams, irrigation ditches, and theborders of pastures and cropland, and it can graduallyinvade perennial crops.

Distribution: In BC it is found in wet to mesic habitatsin the lowland zone and is locally common in thesouthwest of the province, particularly in theVancouver and Victoria areas (Douglas et al. 1998). Itis present in the Kootenay, Okanagan, Mainland,Vancouver Island, and Cariboo regions.

Historical: Introduced from Europe, the plant isthought to have been used to kill Socrates.

Life cycle: Poison hemlock is a biennial that can growup to 3 m tall. In the first year, plants form a smallseedling that resembles wild carrot. Plants usually boltin the second year and produce numerous clusters ofwhite flowers. Plants flower from April through July,and seeds begin in July and continue into winter. Mostseeds mature before dispersal and can germinateimmediately if environmental conditions arefavourable, but some seeds remain dormant (Baskinand Baskin 1990).



Seed bank: Seeds may remain viable in the soil forabout 3 years (Calweed 1997).

Dispersal: Seeds can be spread by machinery, onclothing, or in transported soil. They are also dispersedto a limited extent by water and wind.


Baskin, J. M., and C. C. Baskin. 1990. Seedgermination ecology of poison hemlock. CanadianJournal of Botany 68: 2018–2024.

Calweed Database. 1997. California Noxious WeedControl Projects Inventory. Natural Resource ProjectsInventory, Information Center for the Environment,University of California, Davis.http://endeavor.des.ucdavis.edu/weeds/ [8 Mar 99].

DiTomasso, J. M. 1999. Poison hemlock. In R. L.Sheley and J. K. Petroff, eds. Biology and Managementof Noxious Rangeland Weeds. Corvallis: Oregon StateUniversity Press.


Panter, K. E., and R. F. Keeler. 1988. The hemlocks:Poison hemlock (Conium maculatum) and waterhemlock (Cicuta sp.). In L. F. James, M. H. Ralphs,and D. B. Nielsen, eds. The Ecology andEconomic Impact of Poisonous Plants onLivestock Production. Boulder, CO:Westview Press.

Stubbendieck, J., G. Y. Friisoe, and M. R. Bolick.1995. Poison hemlock. Weeds of Nebraska and theGreat Plains. Lincoln: Nebraska Department ofAgriculture, Bureau of Plant Industry.

US Department of Agriculture. Undated. Poisonhemlock. Western Wetland Flora: Field Office Guideto Plant Species. USDA Soil Conservation Service,West National Technical Center, Portland, OR.Jamestown, ND: Northern Prairie Wildlife ResearchCenter Home Page.http://www.npwrc.usgs.gov/resource/othrdata/WESTFLOR/WESTFLOR.htm [16 Jul 97].

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Poison hemlock. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

William, R. D., D. Bell, T. L. Miller, R. Parker, K. AlKhatib, R. H. Callihan, C. Eberlein, and D. W.Morishita. 1996. Pacific Northwest Weed ControlHandbook. Pullman: Washington State UniversityCooperative Extension.

Biocontrol: Agonopterix alstroemeriana (moth),accidentally introduced into the US, apparently feedsexclusively on poison hemlock. It is found in Coloradoand is a biological control agent in Idaho, Oregon, andWashington, where it is effective (William et al. 1996).This species has not been found in BC.

Mechanical: Poison hemlock can be controlled bydigging, repeated mowing, pulling, or spring/winterburns. Care should be taken to avoid contact with bareskin (wear gloves). Wash hands thoroughly afterhandling any part of this plant.


Herbicides: Picloram, dicamba, 2,4-D, and glyphosatehave been used for chemical control of poisonhemlock. Apply foliar herbicides during the rosettestage with a wick to minimize damage to adjacentdesirable vegetation. Cut any stems that arise aftertreatment. Herbicide treatment may need to be repeatedfor several years until the seed bank is depleted (Panter

and Keeler 1988). Consult the most recent edition ofBC Ministry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Prevent the establishment of newinfestations by eliminating seed production andmaintaining healthy native communities.


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References __________________________________________

Integrated Management SummaryThe tendency of this species to grow in wetareas may restrict the use of certain herbicides.Eliminate seed production and exhaust the soilseed bank by removing seed heads beforeseeds mature. Use gloves for hand-pulling, andavoid touching the plant with bare skin.



Flower: Flowers are yellow, have 5 petals,and are borne solitary on short stalks in the

leaf axils.

Seeds/Fruit: The sharp-pointed fruits are 2–6 mm longand break into 5 sections at maturity. Each sectioncontains 2–4 seeds.

Leaves: Leaves are opposite, hairy, and divided into4–8 pairs of leaflets. Leaflets are oval and 5–15 mmlong.

Stems: Mature plants have numerous trailing stemsthat are 0.6–1.5 m long. The freely branching stemsform mats up to 100 cm wide.

Roots: Taproot.

Seedling: Seedling leaves are oval with a prominentcentral groove.

Similar Species



Agricultural: The hard, spiny burs of puncturevine candamage wool and injure livestock and other animals.Puncturevine can be toxic to livestock, especially sheep(WSU 1999).

Ecological: Forms dense mats on open ground.

Human: The spiny burs can puncture skin and haveeven been known to puncture rubber bicycle tires.

PUNCTUREVINE

Tribulus terrestris L.Family: Zygophyllaceae (Caltrop).


Other Common Names: Goathead, bullhead, Mexican sandbur,Texas sandbur.

Legal Status: Regional Noxious: Okanagan-Similkameen.


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Impacts ____________________________________________


General requirements: In BC, occurs in the drygrasslands of the Interior. It grows along roads,beaches, and in pastures, dry fields, and disturbedhabitats. It can grow in compacted soil, sandy or moistsoils, and rich soils (WSU 1999).

Distribution: Occurs rarely in southern areas of theprovince (Douglas et al. 2000). It is known only fromthe Okanagan at Osoyoos Lake and Oliver. It isclassified as a major concern in the Okanaganagricultural reporting region and is not present in allother agricultural reporting regions. Although it iswidely scattered across much of the US, there is noevidence of spread in BC since the 1970s.


Life cycle: Germinates soon after the first rain inspring and summer but will germinate after any wetperiod. Flowering and seed production occur from Julyto October (Whitson et al. 1996), depending ongeographic location. Flowers are open only in themorning.



Seed bank: May remain dormant 4–5 years (Whitsonet al. 1996).

Dispersal: Spiny burs attach to animals, humans, orthe tires of vehicles.


CWMA. 1999. Puncturevine (Tribulus terrestris).Colorado Weed Management Association.http://www.cwma.org/puncturevine.html [10 Jan 99].

Douglas, G. W., D. Meidinger, and J. Pojar, eds. 2000.Illustrated Flora of British Columbia. Vol. 5:Dicotyledons (Salicaceae through Zygophyllaceae) andPteridophytes. Province of British Columbia.

Washington State University. 1999. Puncturevine.Hortsense Weed Index. http://pep.wsu.edu/hortsense/ [8Mar 99].

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Puncturevine. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: Microlarinus lareynii (stem-boring weevil)has been released in BC but establishment is notknown. Microlarinus lypriformus (fruit-boring weevil)has been released in Colorado.

Mechanical: Can be controlled by digging, hand-pulling, or tilling infestations before flowering andseed production.


Herbicides: Picloram, dicamba, and glyphosate havebeen effective. Consult the most recent edition of BCMinistry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Prevent the establishment of newinfestations by minimizing disturbance, eliminatingseed production and dispersal, and maintainingvigorous perennial plant communities.


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References __________________________________________

Integrated Management SummaryIntegrated management should focus oneliminating seed production and depleting theseed bank. Herbicides may be applicable onupland sites, but the plant is also established onthe lakeshore at Osoyoos Lake, whereherbicides cannot be used. Hand-pulling maybe practised for a small population, but follow-up treatments will be required to ensure long-term control.


Growth form: Perennial forbor woody half-shrub.

Flower: Showy flowers arepurple with 5–7 petals arranged in longvertical racemes.

Seeds/Fruit: Fruits aremany-seeded capsules,seeds are small andovoid.

Leaves: Leaves are simple, entire, andopposite or whorled (Whitson et al.1996).

Stems: Annual stems arise from aperennial rootstock (Mal et al. 1992).Stems are erect and often grow0.5–2.0 m tall. Plants becometaller and bushier over the years asthe rootstock matures.

Roots: Short rhizomes and taproot.


Similar Species

Exotics: Sweet rocket or dames’-violet (Hesperis matronalis), anintroduced mustard rare in south-central BC but frequent in theprovince’s southwest and known onVancouver Island and the adjacentmainland (Douglas et al. 1998).

Natives: Sometimes confused withfireweed (Epilobium sp.), which has 4-petalled flowers.

Agricultural: No information available.

Ecological: Purple loosestrife is an ornamental escapethat occupies wetlands, stream banks, and shallowponds. It can form dense stands that reduce plant andanimal diversity in wetland ecosystems (Bender andRandall 1987). Dense infestations can impede waterflow in canals and ditches. Where it coexists with

cattails (Typha latifolia), it is favoured by fluctuatingwater levels because marsh draw-down helpsloosestrife seedling establishment. Cattails, however,appear able to compete with loosestrife where waterlevels remain constant and relatively deep (FEIS 1996).


PURPLE LOOSESTRIFE

Lythrum salicaria L.Family: Lythraceae (Loosestrife).


Other Common Names: Purple lythrum.



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Impacts ____________________________________________


General requirements: Found in wet areas at low- tomid-elevation in BC. It grows in ditches, irrigationcanals, marshes, stream and lake shorelines, andwetlands (Powell et al. 1994). Some commonassociates include cattail, reed canarygrass (Phalarisarundinacea), sedge (Carex sp.), bulrush (Scirpus sp.),

rush (Juncus sp.), and willow (Salix sp.). The plant cantolerate a wide range of conditions (up to 50% shade),can grow on calcareous and acidic soils (Rutledge andMcLendon. Undated), and will even grow in standingwater. Moisture is required for growth andreproduction, but well-established plants can persist on

dry sites for many years (Powell et al. 1994).

Distribution: Common in the Lower Fraser Valley andfrequent on southern Vancouver Island (Douglas et al.1999). There are also localized pockets in the southOkanagan and Boundary areas. It is regarded as amajor concern in Kootenay, Okanagan, Mainland, andVancouver Island agricultural reporting regions and ispresent in the Thompson and Omineca regions as well.It occurs throughout North America.

Historical: Introduced from Eurasia and first recordedin North America in 1814 (Bender and Randall 1987).

Life cycle: Begins its growth about 7–10 days aftercattail and reed canary grass. Seedlings that establish inthe spring grow rapidly and produce flowers 8–10 weeksafter germination. After flowering, each stem supports adense, spiraling row of dark-brown seed capsules.

Mode of reproduction: By seed and vegetatively fromroots. Detached root or stem fragments can also rootand develop into flowering stems (FEIS 1996).

Seed production: A single flowering stalk can produce300,000 seeds, and densities exceeding 32,000stems/ha have been recorded (FEIS 1996).

Seed bank: Seeds may remain viable for up to 20years.

Dispersal: Seeds are mainly distributed by water, butthey can also be dispersed by animals and humans.Seeds do not drop from capsules until the airtemperature becomes cold in the early autumn.


Bender, J., and J. Randall. 1987. Element stewardshipabstract for Lythrum salicaria, purple loosestrife. TheNature Conservancy, Wildland Weeds Management andResearch Program.http://tncweeds.ucdavis.edu/esadocs/lythsali.html [5Feb 99]


Douglas, G. W., G. B. Staley, D. Meidinger, and J.Pojar, eds. 1998. Illustrated Flora of British Columbia.Vol. 2: Dicotyledons (Balsaminaceae throughCuscutaceae). Province of British Columbia.

Biocontrol: Three agents have been released in theprovince (Powell et al. 1994). Hylobiustransversovittatus (root boring beetle) can seriouslydamage the root system, stunt growth, and reduce seedproduction. Adult weevils emerge in April and feed onloosestrife shoots. Eggs are deposited on the shootbase, and larvae bore into the roots. Two leaf-eatingbeetles, Galerucella calmariensis and Galerucellapusilla, both feed on the foliage and flower heads ofthe plant, and larvae leave the plant and pupate in thesoil (Powell et al. 1994). These have resulted in stuntedgrowth and reduced seed production at numerouscoastal locations.

Mechanical: No information available.


Herbicides: Since purple loosestrife is found in wetsoils, herbicide use is restricted. Glyphosate, triclopyr,and 2,4-D have been used successfully to manage thisplant in the US on some suitable sites. Consult themost recent edition of BC Ministry of Agriculture,Food and Fisheries Crop Production Guides forspecific recommendations. Before applying


Cultural/Preventive: Prevent new infestations byminimizing disturbance and seed dispersal. Hand-pulling isolated plants can be effective on smallinfestations. Pulling should be conducted before plantsset seed. Remove the entire root of the plant to avoidregrowth from root fragments.


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References __________________________________________

Integrated Management SummaryThe key to effective management is earlydetection when infestations are small. Smallinfestations should be eradicated by hand-pulling or herbicide application whereappropriate. It is fairly easy to manage smallnumbers of plants when the seed bank in thesoil is small. Eradicating large population mayonly be possible with biocontrol.


132


Mal, T. K., J. Lovett-Doust, L. Lovett-Doust, and G. A.Mulligan. 1992. The biology of Canadian weeds. 100.Lythrum salicaria. Canadian Journal of Plant Science72: 1305–1330.



Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Purple loosestrife. Weeds of the West. Western Societyof Weed Science, in cooperation with the WesternUnited States Land Grant Universities CooperativeExtension Services, Newark, CA.


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Growth form:Perennial sedge.

Flower: Umbrella-likeclusters of purple to brownspikelets at the end of the floweringstems. The leaf-like bracts underthe flower clusters are shorter thanthe inflorescence.

Seeds/Fruit: Purplish,triangular, and oblong.

Leaves: The basalleaves are linearwith a prominent mid-rib and abruptlytapered point.Leaves are 3–8 mm wideand 5–15 cm long.

Stems: Plants are30–60 cm tall. Stemsare upright, triangular in

cross-section, and as long as or longer than basalleaves.

Roots: Much-branched rhizomes bear many tubers(nutlets). The bitter-tasting tubers areoblong, covered in reddish scales,and often connected in chains.

Seedling: Uncommon, sincemost plants develop from tubers.Leaves are smooth, ribbed, and3-ranked, and stems aretriangular in cross-section.

Similar Species

Exotics: Yellow nutsedge is very similar in appearancebut has yellowish brown spikelets with long, leafybracts, the leaves gradually tapering to a point, and thesmooth, round tubers being borne on the end of therhizomes.


Agricultural: Nutsedges are among the most difficultweeds to control and can rapidly colonize turf,ornamental areas, pastures, and cultivated fields. It is ahighly competitive plant because of its upright growthhabit, rhizomatous root system, and rapid growth.

Ecological: This plant is well adapted to wet, sandysoils and poses a threat to riparian areas wheredisturbance has depleted the native plant community.

Human: Used as an ornamental for water gardens.

PURPLE NUTSEDGE

Cyperus rotundus L.Family: Cyperaceae (Sedge).


Other Common Names: Nutgrass.



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Impacts ____________________________________________


General requirements: Well adapted to moistconditions and sandy soil such as ditches (Whitson etal. 1996).

Distribution: Not yet present in BC but is widelydistributed in Arizona and southern California. Nutletsof purple nutsedge have been discovered in ornamental

nursery stock (roses) imported from Arizona.

Historical: Introduced in North America from Eurasia.

Life cycle: Rhizomes sprout from underground tubersin spring that develop into a bulbil. The bulbil produces2 types of shoots: an upright leafy shoot that producesfood to support the plant, and an underground runner

that establishes another bulbil a short distance from theparent plant. This process is repeated throughout thegrowing season until August, when the plant hasproduced enough food to complete its life cycle thefollowing year (Kopec 1996).

Mode of reproduction: From tubers and occasionallyfrom seed.


Seed bank: No information available on seeds. Tuberscan remain dormant in the soil for extended periods.

Dispersal: Plants spread from rhizomes.


BC Ministry of Agriculture, Food and Fisheries.Undated. Weed Alert—Yellow and Purple Nutsedge.Fact Sheet.

Kopec, D. M. 1996. Purple nutsedge—the war ofattrition. Plant Sciences Department, University ofArizona. http://ag.arizona.edu/turf/glf0696.html

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Purple nutsedge. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: None.

Mechanical: Cutting often stimulates the plant toproduce tubers and nutlets from new rhizomes.Mechanical methods to defoliate the plant must beapplied repeatedly to deplete food reserves in thenutlets and prevent storage of new food.

Fire: Likely to be ineffective because of the extensiveroot system.

Herbicides: The sulfonylurea group of herbicides havebeen effective in managing purple nutsedge.

Up to 3–5 applications/season over 3–4 years may berequired to gain control. A single application may onlystimulate new growth from the tubers (Kopec 1996).Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applying


Cultural/Preventive: Learn to identify this weed.Control new infestations immediately.


135

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References __________________________________________

Integrated Management SummaryPrevention is essential to keeping purplenutsedge out of BC. Public awareness can helpto identify new introductions. Use tillage,mulching, competitive cropping, herbicides,and crop rotation to prevent and manage newinfestations (BC Ministry of Agriculture, Foodand Fisheries. Undated).


Growth form: Perennialgrass.

Flower: Slender spike,resembling wheat heads.

Seeds/Fruit: Spikelets are arrangedin 2 long rows, borne flat side tothe stem. Florets are awnless, orwith short, straight awns.

Leaves: Leaf bladesare flat, pointed, and6–12 mm wide, withsmall, ear-likeappendages(auricles) at thejunction of theblade and sheath(Whitson et al. 1996).

Stems: Mature plants are usually 0.3–1.0 m tall andhave erect stems.

Roots: Rhizomes are yellowish white,cord-like, sharp-pointed, andsomewhat fleshy.

Seedling: Both leaf sheath andblade are hairless or sparselyhairy. Clasping auricles and ashort membranous ligule arepresent (Carey et al. 1993).

Similar Species



Agricultural: Quackgrass reduces productivity incrops, rangeland, and pasture.

Ecological: Quackgrass rapidly invades and quicklystabilizes moist eroding soils. It invades mixed-grass

prairies, stream banks, roadsides, ditches, crop fields,gardens, yards, and disturbed moist areas. It is believedto be allelopathic (Whitson et al. 1996).


QUACKGRASS

Elytrigia repens (L.) Nevski Family: Poaceae (Grass).

Other Scientific Names: Agropyron repens.

Other Common Names: Couchgrass.



136


General requirements: In BC, grows at low- to mid-elevations in fields, gardens, roadsides, and disturbedsites. It is well adapted to moist soils in temperateclimates. The plant is only moderately shade tolerantand vigour is reduced when shading exceeds 50%.

Distribution: Quackgrass is common in southern partsof the province and occurs in all agricultural reportingregions in the province. It is considered a threat to thefine seeds industry in the Peace River. It is widelydistributed in North America.


Life cycle: Rhizomes begin growth in early spring andthen again in autumn with the onset of seasonal rainsand cooler temperatures. Quackgrass flowers from Junethrough August. Cross-pollination is necessary for seedproduction. Seeds germinate in autumn or spring, andplants are capable of producing seeds more than onceper season.

Mode of reproduction: Mainly vegetatively fromroots but also by seed.

Impacts ____________________________________________


Seed bank: Seeds may remain viable for up to 10years.


Hybridization: Although considered a weed,quackgrass is often crossed with other wheat grasses tocreate hybrids for grazing.




Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Quackgrass. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: None.

Mechanical: Very difficult to manage by mechanicalmethods because broken rhizomes quickly regenerate(Rutledge and McLendon. Undated). Mowing canprevent flowering the following season under somecircumstances (FEIS 1996).

Fire: Burning may reduce vigour and abundance(Rutledge and McLendon. Undated).

Herbicides: Many herbicides are available forselective control of quackgrass in crops and non-cropsituations. Consult the most recent edition of BCMinistry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Prevent new infestations byminimizing disturbance and seed dispersal, eliminatingseed production, and maintaining healthy nativecommunities.


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References __________________________________________

Integrated Management SummaryCombining mowing or burning to reduce plantvigour with herbicides may be the mosteffective way to control quackgrass. It mayalso be gradually replaced by other speciesthrough natural succession processes (Rutledgeand McLendon. Undated).



Flower: Flowers areinconspicuous, greenish,

and without petals. They appearin dense, spike-likeclusters up to 20 cmlong at the stem endsand in leaf axils. Spine-tippedbracts give the head a bristlyappearance. Plants flowerfrom June to September,depending on geographic location.

Seeds/Fruit: Fruit is a capsule 1.5–2.0 mm long thatcontains a single glossy black seed.

Leaves: Alternate, dull green leaves have hairs andprominent whitish veins on the underside. Blades 3–8 cmlong are carried on long stalks that often appear to droop.

Stems: Rough, angular stems grow 0.5–1.0 m tall.Plants are usually branched. Stems are red near the

roots and hairy near the tips, with dandruff-like scalesbeneath the flowers (Douglas et al. 1998).

Roots: Short, fleshy taproot is often pinkish to red.

Seedling: Cotyledons are lanceolate with reddish purpleundersides. The stem is dark red near the soil surface.The first leaves are rounded, are notched at the tip, andhave prominent veins (Royer andDickinson 1999).

Similar Species

Exotics: None.

Natives: Several pigweeds native to North Americagrow in BC. Tumble pigweed (Amaranthus albus) andprostrate pigweed (Amaranthus blitoides) bear theirflowers in tiny clusters at the leaf bases instead of inspikes at the end of the stems. Green pigweed(Amaranthus powellii) is a slender plant with longterminal spikes and lacks the upper-stem hairs foundon redroot pigweed (Frankton and Mulligan 1970).

Agricultural: One of the most common agriculturalweeds, this plant infests grains, field crops, orchards,and forages. It causes significant crop yield reductionbecause of its rapid growth and large seed production.When grown on fertile soils, it can accumulate nitratesthat can poison livestock (Alberta Agriculture 1983).This weed is a common soil contaminant and is a hostto several pests of vegetable and ornamental crops,including the tarnished plant bug, European corn borer,

green peach aphid, and several viral diseases (Royerand Dickinson 1999).

Ecological: Grows on disturbed soils, especiallyaround buildings. It is most abundant on fertile soils. Itis unlikely to invade vigorous natural communities anddoes not tolerate shade.

Human: Can cause allergic reactions.

REDROOT PIGWEED

Amaranthus retroflexus L.Family: Amaranthaceae (Amaranth).


Other Common Names: Rough pigweed, red pigweed, greenamaranth.



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Impacts ____________________________________________


General requirements: This weed requires disturbed,open conditions and thrives on fertile soils. It grows incultivated crops, gardens, fields, roadsides, anddisturbed habitats.

Distribution: This plant is present in all agriculturalregions of the province but is more common in thesouth. It is found across North America.

Historical: Native to North America.

Life cycle: Redroot pigweed is an annual thatgerminates late in the spring when the soil has warmed,often after cultivated seedlings have emerged.Germination can continue through the summer withadequate soil moisture (Weaver and McWilliams 1980).Plants can set seed within 8 weeks of germinating,allowing 2 generations per growing season in mostclimates (Royer and Dickinson 1999).


Seed production: Each plant can produce100,000–150,000 seeds.

Seed bank: Seeds are initially dormant, and mostseeds germinate the spring following seeding. Some

seeds can remain dormant in the soil for up to 40 years,but most seeds are unviable after 3 years. Seeds buriedbelow 2.5 cm will not germinate.

Dispersal: By wind, birds, or animals. Farmmachinery, road building, and contaminated seed canalso spread seeds.

Hybridization: Redroot pigweed will often hybridizewith other pigweeds, producing a mixture ofcharacteristics, but the hybrids are often sterile (Weaverand McWilliams 1980).

Alberta Agriculture. 1983. Weeds of Alberta. AlbertaAgriculture and Alberta Environmental Centre.




Weaver, S., and E. L. McWilliams.1980. The biology of Canadianweeds. 44. Amaranthusretroflexus L., A. powellii S. Wats., and A.hybridus L. Canadian Journal of PlantScience 60: 1215–1234.

Biocontrol: None.

Mechanical: Shallow tillage in spring or autumn willencourage redroot pigweed germination. Follow-uptillage or herbicide application is needed to kill theseedlings. Plants up to 4 weeks old are easily killed bycultivation, but older plants often recover fromtrampling, clipping, or other injury (Weaver andMcWilliams 1980). Mowing before flowering willprevent seed-set. Several mowings may be required inone season.

Fire: Fire will clean up herbage and destroy seeds onthe plants but will not affect the seed bank. Improvedfertility from fire may provide an ideal seed bed.

Herbicides: Redroot pigweed is relatively susceptibleto herbicides commonly recommended to controlbroadleaf weeds both pre- and post-emergence. Somepopulations are resistant to triazine herbicides afterrepeated years of application. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Treat new infestationsimmediately. Focus attention on areas with fertile soilslike farmyards, corrals, and manure piles. Till, mow, orhand-pull small populations before they set seed.Maintain healthy perennial plant communities.


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References __________________________________________

Integrated Management SummaryRedroot pigweed is a pioneering speciesadapted to open, fertile conditions. It competesagainst other plants by its rapid growth andprolific seed production. Reducingopportunities for establishment can control thisweed. Till, cut, or hand-pull before largeinfestations establish and a seed bank develops.For large infestations, use appropriateherbicides. Seed disturbed areas to perennialgrasses and forbs and manage livestock tomaintain perennial plant communities.


Flower: Flower heads areproduced along or at the

ends of stems, either individually orin groups of 2–3 (Rees et al. 1996).Each flower head contains 10–12strap-shaped, bright yellow flowersthat are flat across the end withdistinct lobes or teeth. Plants flowerin midsummer until autumn frosts(Powell et al. 1994).

Seeds/Fruit: Seeds are pale brownto nearly black and have awhite pappus.

Leaves: Leaves form in abasal rosette, are sharplytoothed, and wither as theflower stem develops.Rosette leaves are lance-shaped, deeply lobed, and 5–13 cmlong. Stem leaves are inconspicuous,

narrow, and entire (Whitson et al. 1996).

Stems: Mature plants are 0.4–1.0 m tall. Lower stemshave short, downwardly bent, coarse hairs.Upper stems are smooth.

Roots: Deep, extensive root system.


Similar Species

Exotics: There are 3 forms of rushskeletonweed in the US, each differing inthe morphology of their inflorescence and theirsusceptibility to control measures (Sheley et al. 1999).It has not been clearly established if all 3 forms occurin BC.

Natives: Sometimes confused with rushlike skeleton-plant (Lygodesmia juncea), which has pink(occasionally white) flowers and grows in the southernInterior.

Agricultural: Infestations of rush skeletonweed canreduce livestock and wildlife forage (Sheley et al.1999). The extensive and deep root system makes theplant difficult to manage (Whitson et al. 1996).

The latex the plant produces can cause seriousproblems with crop harvest machinery when the plantestablishes on cropland (Rees et al. 1996). Rushskeletonweed can provide limited value as forage

during a drought. Rosette leaves and pre-floweringstems are palatable and nutritious.

Ecological: In the US, rush skeletonweed has formeddense monocultures that displace native plants, but itrarely invades healthy native communities (Sheley etal. 1999).


RUSH SKELETONWEED

Chondrilla juncea L.Family: Asteraceae (Sunflower).


Other Common Names: Skeletonweed, gum succory, devil’s-grass,naked weed, hog-bite.



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Impacts ____________________________________________


General requirements: Rush skeletonweed occupiesrangelands, roadsides, and disturbed habitats at mid-elevations in the dry grassland zone of the province(Powell et al. 1994). It generally inhabits well-drained,light-textured soils. It is capable of growing in a widerange of conditions but appears best adapted to areasthat have cool winters, warm summers, and apredominance of winter and spring rainfall (Rees et al.1996). This species grows in disturbed habitats and inovergrazed rangeland, especially in the US PacificNorthwest and California (Sheley et al. 1999).

Distribution: Infestations occur in the Vernon area,Crescent Valley, Kimberley, Windermere, and Creston.Rush skeletonweed presently is regarded as a majorconcern in the Kootenay and Okanagan agriculturalreporting regions.

Historical: Introduced from southern Europe.

Life cycle: A tap-rooted perennial forb.

Mode of reproduction: By seed and vegetatively fromroots. Plants reach 0.4–1.0 m tall at maturity. Rosettesdevelop from root buds in the autumn (Powell et al.1994) or from germinating seed.

Seed production: A single multi-stemmed plant mayproduce as many as 15,000–20,000 seeds.


Dispersal: Seeds are dispersed by wind, water,animals, and humans.


Biocontrol: Aceria chondrillae (gall mite) andPuccinia chondrillina (stem and leaf rust) have beenreleased in BC. The gall mite appears to be effective indistorting the growth of the plant, but no data areavailable to assess its effect on rush skeletonweedpopulations. Puccinia chondrillina has had impacts onthis species in California (Supkoff et al. 1988).Rotational grazing with sheep can control rushskeletonweed if the weeds are grazed at a moderatelevel while desirable plants are grazed lightly (Sheleyet al. 1999).

Mechanical: Hand-pulling can be used on smallinfestations, but repeated treatments will likely berequired because of the plant’s extensive root system.Mowing and cultivation are ineffective at controllingrush skeletonweed (Sheley et al. 1999).


Herbicides: Picloram has been effective when appliedto rosettes (Sheley et al. 1999). Repeated applicationsof a mixture of glyphosate and dicamba have also beeneffective on rush skeletonweed populations inCalifornia (Calweed 1997). Similarly, annualapplications of a mixture of clopyralid and dicambaprovided 95% control of rush skeletonweed inAustralia over 3 years (Heap 1993). Herbicides should

be applied after the plant has bolted but before it setsseed. Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions. Cultural/Preventive:Prevent establishment of new infestations. Manageland use to maintain vigorous native communities.Seed disturbed areas to desirable perennial species.


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Management ________________________________________

Integrated Management SummaryRush skeletonweed is not widely spread in theprovince and it is thus important that newinfestations be identified early and dealt withimmediately. Hand-pulling, cutting to preventseed-set, and herbicide applications should allbe considered for early treatment. Reportoccurrences of this plant immediately to theweed specialists in the Ministry of Agriculture,Food and Fisheries, the Ministry of Forests, oryour Regional District Weed Coordinator.


142

Calweed Database. 1997. Noxious weeds project list.California Noxious Weed Control Projects Inventory.Natural Resource Projects Inventory, InformationCenter for the Environment, University of California,Davis. http://endeavor.des.ucdavis.edu/weeds/ [17 Dec98].

Heap, J. W. 1993. Control of rush skeletonweed withherbicides. Weed Technology 7: 954–959.


Rees, N. E., P. C. Quimby, Jr., G. L. Piper, E. M.Coombs, C. E. Turner, N. R. Spencer, and L. V.Knutson (eds). 1996. Biological Control of Weeds inthe West. Western Society of Weed Science, incooperation with USDA Agricultural Research Service,Montana Department of Agriculture, and MontanaState University.

Sheley, R. L., J. M. Hudale, and R. T. Grubb. 1999.Rush skeletonweed. In R. L. Sheley and J. K. Petroff,eds. Biology and Management of Noxious RangelandWeeds. Corvallis: Oregon State University Press.

Supkoff, D. M., D. B. Joley, and J. J. Marois. 1988.Effect of introduced biological control organisms onthe density of Chondrilla juncea in California.Biological Control Services Program, CaliforniaDepartment of Food and Agriculture, and Departmentof Plant Pathology, University of California, Davis.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Rush skeletonweed. Weeds of the West. WesternSociety of Weed Science, in cooperation with theWestern United States Land Grant UniversitiesCooperative Extension Services, Newark, CA.

References __________________________________________


143


Flower: The flower heads of Russianknapweed are urn-shaped, solitary, and

composed of disk flowers only (Zimmerman 1996).Floral bracts are broad, ovoid,entire, and greenish at thebase, with papery,finely hairy edges.Flowers arenumerous, all tubular.The petals are pink orpurple, turning strawcoloured at maturity.

Seeds/Fruit: Seeds are ovaland compressed. Seeds aregreyish or ivory, with longwhite bristles(pappus) at the tipwhen young, butthese fall from theseed as it matures.

Leaves: Leaves are alternate.Lower stem leaves are narrowlyoblong to lance-shaped, and deeplylobed. The upper leaves are oblong

and toothed and become progressively smaller.Rosette leaves are lance-shaped, tapering atboth ends with the broadest part at the tip.

Stems: Mature plants are 0.45–1.0 m tall.The stems are erect, thin, stiff, branched,and when young are covered with soft, short, grey hair(Zimmerman 1996).

Roots: Russian knapweed’s well-developed rootsystem functions as the major means of propagationand spreading. The roots are easily recognizable bytheir black or dark brown colour and presence of small,alternately arranged scale leaves, which support budsin their axils (Zimmerman 1996).

Seedling: The cotyledons (seed leaves) areoval. The first true leaves are alternate andlanceolate with shallow toothed or smoothedges. The surface of the leaves looks greyishgreen but is not hairy.

Similar Species

Exotics: Russian knapweed can be distinguished fromother knapweeds by the pointed papery tips of thefloral bracts.

Natives: Many native members of Asteraceae resembleknapweed in the rosette stage.

Agricultural: Reduces yield and quality of cerealcrops and is toxic to horses. Plant extracts have beenshown to be inhibitory to growth of other plants.

Ecological: Russian knapweed forms dense stands thatcan displace native species and reduce forageproduction (Whitson 1999). Once established, the plantextends in all directions and can cover an area of 3.6m2 within 2 years (Watson 1980). Russian knapweedcontains allelopathic compounds that inhibit the growthof competing plants (Stevens 1986). Tests conducted

with alfalfa (Medicago sativa), barnyard grass(Echinochloa crusgalli), and red millet (Panicummiliaceum) revealed it inhibited root elongation ofgrasses and broad-leaved plants by 30% when thepolyacetylene compound is at a soil concentration of 4parts per million (Stevens 1986). This allelopathiceffect, combined with dense vegetative reproduction,allows Russian knapweed to colonize and dominatenew sites quickly.


RUSSIAN KNAPWEED

Acroptilon repens (L.)Family: Asteraceae (Sunflower).

Other Scientific Names: Centaurea repens.

Other Common Names: Turkestan thistle, mountain bluet,creeping knapweed.

Legal Status: Regional Noxious: North Okanagan.


144

Impacts ____________________________________________


General requirements: Russian knapweed occurs insouthern BC east of the Coast-Cascade mountains inlow- to mid-elevation grasslands and forests. Itcommonly grows along roadsides, riverbanks,irrigation ditches, pastures, clear-cuts, cropland, anddisturbed habitats. It is not restricted to any particularsoil but does especially well in clay soils. Selleck(1964) observed that infestations increased in drylocations but decreased in moist locations due tocompetition with perennial grasses.

Distribution: Russian knapweed is found in the southof the province east of the Coast-Cascade Mountains(Douglas et al. 1998), particularly in warm valleybottoms (Powell et al. 1994). It is considered a majorproblem in the Okanagan agricultural reporting regionand is present in the Kootenay, Okanagan, Thompson,and Peace River areas.

Historical: Introduced from Eurasia, probably as acontaminant in crop seed.

Life cycle: Russian knapweed has an extensive root

system and low seed production and is very persistent.It is a strong competitor and can form dense colonies indisturbed areas. Russian knapweed spreads byrhizomes and seed. Shoots emerge early in spring. Allshoot development originates from root-borne stembuds (Watson 1980). Buds arise adventitiously atirregular intervals along the roots. Plants form rosettesand bolt in late May to mid-June, depending onlocality. The plant flowers from June to October(Zimmerman 1996).

Mode of reproduction: Primarily vegetatively;possibly by seed.

Seed production: A single plant may produce 1,200seeds/year.

Seed bank: Seeds may remain viable 2–8 years(Carpenter and Murray 1998).

Dispersal: Knapweed seeds are often spread in hayand on vehicle undercarriages.


Biocontrol: Subanguina picridis (nematode) has beenexperimented with as a biocontrol agent in BC andColorado but is not available for general distribution.

Mechanical: Cutting or removal of the above-groundportion of the plant reduces the current-year growthand may eliminate seed production, but it will not killRussian knapweed. Cutting several times before theplants bolt stresses Russian knapweed plants and forcesthem to use nutrient reserves stored in the root system.The plants that re-emerge are usually smaller in sizeand less vigorous. Once plants have bolted, there areno more buds on the roots capable of reproduction untilbuds begin to form again in mid-August to September.


Herbicides: Picloram is considered the most effectiveherbicide for Russian knapweed regardless ofapplication time (Duncan 1994). Clopyralid is alsoeffective and has little or no impact on many otherforbs. Whitson (1999) found that combinations ofpicloram, clopyralid, and 2, 4-D were effective formanaging Russian knapweed in Wyoming at the bloomor seed stage. Benz et al. (1999) found that clopyralid+ 2,4-D treatment of Russian knapweed in the latebloom stage followed by autumn seeding of a

bunchgrass and a sod-forming grass was the mosteffective management method. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Maintain perennial nativecommunities, and minimize disturbance and seeddistribution.


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Management ________________________________________

Integrated Management SummaryA combination of cutting and herbicides can beused to manage Russian knapweed. In theautumn, apply picloram to plants that have re-emerged. Repeated applications may berequired for several years to exhaust the soilseed bank. The most effective method ofcontrol for Russian knapweed is to prevent itsestablishment, maintaining vigorous perennialplant communities. Seed disturbed sites toperennial grasses to provide competition.


146

Beck, K. G. 1996. Russian knapweed. Colorado StateUniversity Cooperative Extension Natural ResourceSeries, No. 3. 111.http://www.ext.colostate.edu/pubs/natres/03111.html[24 Jan 00].

Benz, L. J., K. G. Beck, T. D. Whitson, and D. W.Koch. 1999. Reclaiming Russian knapweed infestedrangeland. Journal of Range Management 52:351–356.

Carpenter, A. T., and T. A. Murray. 1998. Elementstewardship abstract for Acroptilon repens. The NatureConservancy, Wildland Weeds Management andResearch Program.http://tncweeds.ucdavis.edu/esadocs/acrorepe.html [19Jan 99].


Duncan, C. L. 1994. Knapweed. Cooperative extension.Vol. 8. 3. Washington State University, US Departmentof Agriculture, and Washington Counties.

Maddox, D. M., A. Mayfield, and N. H. Poritz. 1985.Distribution of yellow starthistle (Centaureasolstitialis) and Russian knapweed (Centaurea repens).Weed Science 33: 315–327.


Rees, N. E., P. C. Quimby, Jr., G. L. Piper, E. M.Coombs, C. E. Turner, N. R. Spencer, and L. V.Knutson, eds. 1996. Biological Control of Weeds in theWest. Western Society of Weed Science, in cooperationwith USDA Agricultural Research Service, MontanaDepartment of Agriculture, and Montana StateUniversity.

Selleck, G. W. 1964. A competition study of Cardariasp. and Centaurea repens. Proceedings of the 7thBritish Weed Control Conference. pp. 569–576.

Stevens, K. L. 1986. Allelopathic polyacetylenes fromCentaurea repens (Russian knapweed). Journal ofChemical Ecology 12: 1205–1211.

Watson, A. K. 1980. The biology of Canadian weeds.43. Acroptilon (Centaurea) repens (L.) DC. CanadianJournal of Plant Science 60: 993–1004.

Whitson, T. D. 1999. Russian knapweed. In R. L.Sheley and J. K. Petroff, eds. Biology and Managementof Noxious Rangeland Weeds. Corvallis: Oregon StateUniversity Press.

Zimmerman, J. A. C. 1996. Ecology and distribution ofAcroptilon repens (L.) DC, Asteraceae. USGSColorado Plateau Field Station, Southwest Exotic PlantMapping Project.

References __________________________________________


147



Flower: Inconspicuous flowers are borne inaxils of the upper leaves. Each flower is

accompanied by a pair of spiny floral bracts (Whitsonet al. 1996).

Seeds/Fruit:Small, one-seeded fruitswith wingedtips. Seeds areround, black,smooth, andshiny.

Leaves:Leaves arealternate; the first leavesare long, string-like, and soft.

Later leaves are short, scale-like, and tipped with a stiffspine (Whitson et al. 1996).

Stems: Mature plants are 0.1–1.0 m tall and arerounded, bushy, and highly branched. Stems are red orpurple striped.

Roots: The root system consists of ataproot that can grow 1 m or more indepth with extensive lateral roots.

Seedling: Seedling plants have long,fleshy leaves.

Similar Species

Exotics: Small kochia (Kochiascoparia) plants can sometimes looksimilar.


Agricultural: Well adapted to cultivated drylandagriculture but also found on disturbed rangeland anddisturbed habitats.

Ecological: Russian thistle colonizes barren desertareas that cannot support other flora and invades manydifferent disturbed plant communities. Since itsintroduction it has become one of the most commonand troublesome weeds in the drier regions of the US

(Whitson et al. 1996). It occurs in many communitiesand is most common along disturbed grassland anddesert communities. In disturbed big sagebrushcommunities, it dominated for the first 2 years. Plantsthen became overcrowded and stunted and werereplaced by mustards (FEIS 1996).


RUSSIAN THISTLE

Salsola kali L. Family: Chenopodiaceae (Goosefoot).


Other Common Names: Tumbleweed.



148

Impacts ____________________________________________


General requirements: In BC, Russian thistle growsat low- to mid-elevations along roadsides, railroadtracks, fields, and disturbed or unoccupied sites. Itgrows on well-drained, uncompacted soil with a sunnyexposure. It cannot tolerate saturated soil for extendedperiods.

Distribution: Frequent in southern areas of theprovince (Douglas et al. 1998), Russian thistle is foundthroughout central and western North America.


Life cycle: Russian thistle is capable of germinatingover a wide range of seedbed temperatures (FEIS 1996).

Plants usually flower from July through October,depending on geographic location. Seeds mature duringAugust through November. Seedlings are poorcompetitors and do not establish in communities withhigh plant density (FEIS 1996).


Seed production: One plant can produce up to about250,000 seeds (Cranston et al. 1996).

Seed bank: Seeds remain viable less than a year.

Dispersal: After seeds mature in the autumn the plantstem separates from the root, and the plant tumbles inthe wind.


Calweed Database. 1997. California Noxious WeedManagement Projects Inventory. Natural ResourceProjects Inventory, Information Center for theEnvironment, University of California, Davis.http://endeavor.des.ucdavis.edu/weeds/ [6 Jan 99].

Cranston, R., D. Ralph, and B. M. Wikeem. 1996.Field Guide to Noxious and Other Selected Weeds ofBritish Columbia. BC Ministry of Agriculture, Foodand Fisheries and Ministry of Forests.

Crompton, C. W., and I. J. Bassett. 1985. The biologyof Canadian weeds. 65. Salsola pestifer A. Nels.Canadian Journal of Plant Science 65: 379–388.

Douglas, G. W., D. Meidinger, and J. Pojar, eds. 1998.Illustrated Flora of British Columbia. Vol. 2:Dicotyledons (Balsaminaceae throughCuscutaceae). Province of British Columbia.


Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Russian thistle. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: None available in BC.

Mechanical: Mowing or pulling young plants can beused to manage Russian thistle. Repeated applicationsover several years may be required for successfulmanagement.

Fire: Prescribed burning is not recommended formanaging the plant because it colonizes disturbedhabitats such as burned areas (FEIS 1996).

Herbicides: Dicamba and glyphosate have beensuccessfully used to manage Russian thistle (Calweed1997). Numerous herbicides are registered for controlin crop situations. Consult the most recent edition ofBC Ministry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.



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Management ________________________________________

References __________________________________________

Integrated Management SummaryRussian thistle only can be managed byeliminating seed production and by depletingthe soil seed bank. Cut, pull, or treat plantswith herbicide before seed-set. Seed disturbedareas to perennial grasses.


Growth form: Annual, biennial, orsometimes perennial forb.

Flower: Single white daisy-like flowerswith yellow centres at the end of eachstem. The numerous bractsof the flower head arearranged in overlappingrows. The receptacle lacksscales. Flowers from June toOctober.

Seeds/Fruit: Seeds are about 2 mmlong, dark brown, with 3 ribs on oneside and a broad central brown areaon the other (BC Ministry ofAgriculture and Food 1984).

Leaves: Basal leaves disappear byflowering time. The stem leaves arealternate, usually smooth, and finelydivided into short, thread-like segments.Leaves are odourless when crushed.

Stems: Mature plants are 5–100 cm tall. The stems areerect to semi-erect, smooth, and branched.

Roots: Extensive, fibrous root system.

Seedling: The cotyledons (seed leaves) are roundedand stalkless. The first leaves are divided into narrowsegments (Royer and Dickinson 1999).

Similar Species

Exotics: Several introduced plants have flowers andleaves similar to scentless chamomile. Leaves of wildchamomile (Matricaria recutita), stinking mayweed(Anthemis cotula), and pineapple weed (Matricariadiscoidea) have a strong odour when crushed, whilescentless chamomile leaves are almost odourless. Cornchamomile (Anthemis arvensis) has stems that are hairybelow the heads, and the receptacle has scales (Franktonand Mulligan 1970). Oxeye daisy (Leucanthemumvulgare) has similar flowers, but the leaves on scentlesschamomile are much more finely dissected.

Natives: None.

Agricultural: Reduces yields in grain and seed fields,hayfields, pastures, and cultivated crops. On cropland,it is most problematic in areas with high soil moistureand minimal tillage (Harris and McClay 2001). It isunpalatable to livestock and can form dense stands inpastures and hayfields (Alberta Agriculture 1994).

Ecological: This plant is well adapted to heavy soilsaround shorelines and watercourses, and it germinatesunder periodic flooding conditions, which allows nearmonocultures to grow near ponds, streams, and otherfrequently flooded areas (Alberta Agriculture 1995).


SCENTLESS CHAMOMILE

Matricaria perforata MeratFamily: Asteraceae (Sunflower).

Other Scientific Names: Matricaria maritima var. agrestis;Matricaria maritima var. inodoura.

Other Common Names: Scentless mayweed, false chamomile.



150


General requirements: Grows from low- to mid-elevations in BC and is found on dry shorelines,roadsides, fencelines, disturbed areas, and perennialforage crops.

Distribution: Present in all of the province’s

agricultural regions and is a major concern in theKootenay, Okanagan, Peace River, and Thompsonregions. It occurs in all provinces of Canada but ismost common in the Maritimes and Prairies.


Impacts ____________________________________________

Life cycle: Annual, biennial, or short-lived perennial.Seedlings may emerge anytime from spring to autumn.The early-emerging plants flower during the year ofgermination, but later-emerging plants overwinter todevelop into a large, multiple-branched plant.Flowering can occur from May to October, dependingon geographic location, with overwintering plantsflowering first. The plant has a long flowering season,and seeds are viable as soon as the flower is formed(Alberta Agriculture 1985).


Seed production: Up to a million seeds can beproduced by each plant and up to 1.8 million seeds/m2

can be produced in a dense stand (Alberta Agriculture1995).

Seed bank: Seeds remain viable longer in undisturbedsoil than in cultivated land.

Dispersal: Seeds float readily on water so that firstinfestations are often around watercourses (AlbertaAgriculture 1985). Seeds also disperse in contaminatedcrop seed, in animal feed, and on equipment.


Alberta Agriculture. 1985. Weeds of Alberta. Agdex640–4. Co-publishers: Alberta Agriculture and AlbertaEnvironmental Centre.

Alberta Agriculture. 1997. Scentless chamomile:Biology and management.http://www.agric.gov.ab.ca/agdex/600/6406.html

Alberta Agriculture. 1994. Scentless chamomile:Biology and control. Agdex 640–6. Co-publishers:Alberta Agriculture and Alberta Environmental Centre.

BC Ministry of Agriculture and Food 1984. Scentlesschamomile. Agdex 640 Fact Sheet.


Vol. 1: Gymnosperms and Dicotyledons (Aceraceaethrough Asteraceae). Province of British Columbia.


Harris, P., and A. McClay. 2001. Scentlesschamomile—Matricaria perforata Metat. Lethbridge,AB: Agriculture and Agri-Food Canada.


Biocontrol: The seed-head weevil (Omphalapionhookeri) and the stem-boring weevil (Microplontusendentulus) have both been released in BC. Monitoringis required to determine impact.

Mechanical: Frequent shallow tillage will manageseedlings effectively by encouraging germination ofseeds after the current seedlings have been destroyed.Plants are less likely to re-establish if soils are tilledduring hot, dry weather and before plants flower. Seedproduction can be reduced if plants are mowed beforethey flower in pastures, hay land, and non-crop land.Scentless chamomile produces new flowers below thecutting height of the swather. Mowing will be effectiveonly if the stands are mowed early and often, with eachsuccessive mowing lower than the previous one(Alberta Agriculture 1997).

Fire: Burning seed heads can be effective to preventspread.

Herbicides: Picloram, dicamba, and MCPP have beeneffective in non-crop areas. Apply herbicides early inthe season before flowering. Consult the most recentedition of BC Ministry of Agriculture, Food and

Fisheries Crop Production Guides for specificrecommendations. Before applying herbicides readthe label for full use and precautionary instructions.

Cultural/Preventive: Hand-pulling can prevent spreadinto new areas and can be effective on smallinfestations. Scentless chamomile does not competewell with vigorous plants. Avoid disturbance in naturalareas and graze moderately to maintain competitiveperennial plant communities (Alberta Agriculture1997).


151

Management ________________________________________

References __________________________________________

Integrated Management SummaryManagement can be achieved throughprevention of seed production and competitionfrom desirable plants. An integrated approachusing tillage, mowing, and cropping can beused to manage this plant (Alberta Agriculture1997).


Growth form: Biennial or perennial forb.

Flower: Flower heads are numerous,2.5–5.0 cm in diameter,

with spine-tipped bracts. Flowersare violet to reddish.

Seeds/Fruit: One-seededfruit (achene) iswrinkled, brown togreyish black, andtipped with a plume(pappus) of slenderbristles (Stubbendiecket al. 1995).

Leaves: Leaves arealternate, very large, andirregularly lobed, andhave sharp yellow spikes.Rosette leaves may be upto 60 cm long and 30 cmwide (Whitson et al. 1996).

Upper and lower leaf surfaces are coveredwith a thick mat of cotton-like or woollyhairs, giving the foliage a grey-greencolour (Dewey 1991).

Stems: Mature plants can be1.5–3.0 m tall. Stems are numerousand branched and have broad,spiny wings and woolly hairs.

Roots: Thick, fleshy taproot.


Similar Species

Exotics: Scotch thistle is the only member of thisgenus in BC (Douglas et al. 1998).

Natives: None.

Agricultural: Can be competitive with desirable nativeforage species when it forms dense stands that areimpenetrable to livestock. This species canoccasionally invade field crops.



SCOTCH THISTLE

Onopordum acanthium L. Family: Asteraceae (Sunflower).


Other Common Names: Cotton thistle, winged thistle.

Legal Status: Regional Noxious: North Okanagan.


152

Impacts ____________________________________________


General requirements: In BC, Scotch thistle is foundat low elevations along roadsides and disturbed areas(Douglas et al. 1998). It also grows in irrigationditches, in disturbed habitats, and on rangelands. Theseeds contain a water-soluble germination inhibitor, soit is often successful in moist areas that are adjacent toriparian or sub-irrigated areas along stream courses.

Distribution: Present only and regarded as a majorconcern in the Okanagan.


Life cycle: A biennial that produces a large, ground-level rosette the first year and a tall, spiny plant in thesecond year. Flowering occurs from mid-June toSeptember, depending on location.


Seed production: Individual plants can produce70–100 flowering heads, each containing 100–140seeds (Young and Evans 1969).

Seed bank: Seeds may remain viable in the soil forover 30 years.

Dispersal: Mainly by wind. Seeds can be dispersed byattaching to clothing or animal fur, or by transport inhay, machinery, or water.


Beck, K. G. 1991. Biennial thistle control withherbicides. In L. F. James, J. O. Evans, M. H. Ralphs,and R. D. Child, eds. Noxious Range Weeds. Boulder,CO: Westview Press.

Beck, K. G. 1999. Biennial thistles. In R. L. Sheley andJ. K. Petroff, eds. Biology and Management of NoxiousRangeland Weeds. Corvallis: Oregon State UniversityPress.

Dewey, S. A. 1991. Weedy thistle of the westernUnited States. In L. F. James, J. O. Evans, M. H.Ralphs, and R. D. Child, eds. Noxious Range Weeds.Boulder, CO: Westview Press.


Stubbendieck, J., G. Y. Friisoe, and M. R. Bolick.1995. Scotch thistle. Weeds of Nebraska and the GreatPlains. Lincoln: Nebraska Department of Agriculture,Bureau of Plant Industry.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Scotch thistle. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

Young, J. A., and R. A. Evans. 1969. Germination andpersistence of achenes of Scotch thistle. Weed Science20: 98–101.

Biocontrol: None.

Mechanical: Mowing or hand-cutting are usually mosteffective in combination with other methods. Plants canregrow from severed roots, and cut stems may stillproduce viable seed.


Herbicides: Picloram, dicamba, 2,4-D, and clopyralidhave been effective in managing Scotch thistle.Combinations of dicamba and 2,4-D, or clopyralid and2,4-D, have also been used. Herbicides should beapplied in spring before the plant bolts or in theautumn to rosettes (Beck 1991). Metsulfuron-methyl iseffective after bolting begins (Beck 1999). Consult themost recent edition of BC Ministry of Agriculture,Food and Fisheries Crop Production Guides forspecific recommendations. Before applying


Cultural/Preventive: Maintain a strong, competitiveperennial plant cover.


153

Management ________________________________________

References __________________________________________

Integrated Management SummaryManagement has been effective when thetaproot is cut 2.5–5.0 cm below the ground anda follow-up application of herbicides occurs.New infestations should be dealt withimmediately. Manage livestock grazing tomaintain vigorous native plant communitiesand seed disturbed areas to perennial plants.


Growth form: Annual or perennial creepingforb.

Flower: Smallflowers form in narrowpanicles at the end of thestems. Flower stalks arejointed near the base of theflower (Douglas et al. 1999).Male and female flowers areborne on separate plants. Maleflowers are orange-yellow andfemale flowers are red-orange(Cranston et al. 2000). In femaleflowers the inner sepals tightlyenclose the seeds.

Seeds/Fruit: Smooth, shiny seedsare triangular, reddish brown,about 1.5 mm long.

Leaves: Basal leaves are mostly arrow-shapedwith lobes pointed outward, but some may belinear or egg-shaped. Leaves are smooth withblades 1–5 cm long and stalks often are longerthan the blades (Douglas et al. 1999). Stem leavesare alternate and nearly without stalks. Leaveshave a distinctive sour taste.

Stems: Smooth, wiry, unbranched below theinflorescence, and 15–30 cm tall.

Roots: Slender, much-branched rhizomes.


Similar Species

Exotics: Garden sorrel (Rumex acetosa) has similararrowhead-shaped leaves, but the leaf lobes pointdownward, and it is an annual plant with a taproot.

Natives: No native sorrels resemble sheep sorrel.

Agricultural: Infests meadows and pastures, often onpoorly drained or impoverished soils. Sheep sorrel canresult in forage seeding failures on soils with large seedbanks (Frankton and Mulligan 1970). A commonproblem in turf as well.

Ecological: Commonly occupies roadsides, fields,

pastures, and other disturbed habitats, especially onsandy soils or where recent fires have occurred. Heavyinfestations may inhibit re-establishment of nativespecies (Northern Prairie Wildlife Research Center.Undated).


SHEEP SORREL

Rumex acetosella L.Family: Polygonaceae (Buckwheat).

Other Scientific Names: Rumex angiocarpus.

Other Common Names: Field sorrel, red sorrel, sourgrass.



154


General requirements: Tolerates a wide range of soilconditions from acid to alkaline but is most commonon soils with low fertility. In BC, it is found in gardens,lawns, pastures, roadsides, meadows, and disturbedareas.

Distribution: Found in all agricultural regions, but it is

most common in southern BC. It occurs in allprovinces and throughout the US.


Life cycle: Perennial that quickly develops spreadingrhizomes after germination. The rhizomes producewhitish buds that grow into leafy above-ground shoots

Impacts ____________________________________________

and result in very dense patches. The plant may growas an annual that completes its life cycle in onegrowing season.

Mode of reproduction: By seeds and creepingrhizomes.

Seed production: About 250 seeds/plant.


Dispersal: By wind, water, and vehicles. Soildisturbance spreads rhizomes, which re-establish.






Biocontrol: None.

Mechanical: Cultivation can be effective in controllingthis species, but inadequate treatments may spreadrootstocks of established plants. Effective cultivationrequires repeated and frequent removal of topgrowthfor one or more seasons, which will eventually starvethe roots. Plants are generally too low to be affected bymowing.

Fire: Fire probably kills topgrowth but may not affectrhizomes.

Herbicides: Many herbicides are registered for control.Control is most effective on actively growing, youngplants. Consult the most recent edition of BC Ministryof Agriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Competitive crops resistinvasion of this weed. Application of lime or fertilizer

(especially nitrogen) favours desirable plants.Deteriorating pastures may require reseeding.Companion crops help impede population growth ofthis weed while the forage seedlings get established.


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References __________________________________________

Integrated Management SummaryEarly detection is important to limitestablishment of mature plants and largeinfestations. Hand-pull plants before matureplants establish extensive root systems withrhizomes. Apply herbicides to control matureplants and seed disturbed areas to perennialgrasses and forbs to provide cover andcompetition against this weed.


Growth form: Annual or winter annual.

Flower: The inflorescence isa long, many-flowered

raceme. Flowers are clustered at theend of slender, spreading stalks 7–15mm long (Douglas et al. 1998). Eachtiny flower has 4 notched petals.

Seeds/Fruit: Fruit are flattenedtriangular or heart-shaped podsresembling a purse. Stalks elongateafter the pods develop.

Leaves: Basal leaves are stalked,deeply lobed, and hairy, and form arosette. Stem leaves are alternate andunstalked, and clasp the stems.

Stems: Stems are erect and simple orbranched at the base. Stems grow 10–90cm tall and are covered with grey hairs.

Roots: Thin, branched taproot.

Seedling: Cotyledons arerounded and long-stalked with agrainy appearance. The firsttrue leaves are opposite withnumerous star-shaped hairs(Royer and Dickinson 1999).

Similar Species

Exotics: Stinkweed (Thalspiarvense) also has flattened seedpods on stalks along a raceme,but it has much larger seed podsand the whole plant is completelysmooth.

Natives: Some species of rock cress(Arabis sp.) resemble shepherd’s purse,but none have the distinctive purse-shaped pods.

Agricultural: This weed of cultivated fields, rowcrops, hayfields, and pastures can seriously reduce cropyield. It is a host to many viral diseases as well as to afungus that attacks vegetables in the mustard family(Royer and Dickinson 1999).

Ecological: Common on disturbed areas in native plantcommunities but impacts poorly understood.


SHEPHERD’S-PURSE

Capsella bursa-pastoris (L.) Medic.Family: Brassicaceae (Mustard).





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General requirements: This plant grows under a widerange of environmental conditions. It is found incultivated fields, hayfields, gardens, and roadsides andother disturbed areas. It is commonly found on slashpiles on logged areas.

Distribution: Shepherd’s purse grows in allagricultural regions of the province and is found intemperate regions around the world.


Life cycle: The annual form germinates in the springor summer and produces seed the first year. Winterannuals germinate late in summer or in autumn,overwinter as rosettes, and set seed the following year.


Seed production: One plant may produce up to 40,000seeds.

Seed bank: Both dormant and non-dormant seeds areformed. Non-dormant seeds germinate readily at highor alternating temperatures and account for seedlingsemerging late in the season. Dormant seeds are verylong-lived in the soil and will remain dormant if burieddeeper than 2 mm (Holm et al. 1977). Dormancy canbe broken with exposure to light following a period ofcool temperatures (below 15o C). These conditions aremet with spring tillage.

Dispersal: Seeds can be dispersed through ingestion bybirds or animals, or spread on vehicles, on equipment,or in hay.



Holm L. G., D. L. Plucknett, J. V. Pancho, and J. P.Herberger. 1977. The World’s Worst Weeds—Distribution and Biology. Honolulu: University ofHawaii Press.


Biocontrol: None.

Mechanical: Small infestations can be hand-pulled ortilled. Frequent cultivation of summerfallow orunplanted areas will bring seeds to the surface andmaximize germination. Repeated harrowing may berequired in infested fields before reseeding.

Fire: Fire is ineffective.

Herbicides: Numerous herbicides are available forcontrol of shepherd’s purse. Their selection depends onthe crop and environmental conditions. Consult themost recent edition of BC Ministry of Agriculture,Food and Fisheries Crop Production Guides forspecific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Monitor disturbed areas for newoutbreaks. Maintain strong perennial stands in pastures.

If necessary, reseed deteriorating stands. Prevent seed-set on established infestations by mowing or herbicideapplication.


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References __________________________________________

Integrated Management SummaryIntegrated management may require acombination of mechanical, cultural, andchemical treatments, depending on aninfestation’s size and location. On cropland,this plant can be a significant weed, but onnon-cropland it is often regarded as a nuisancewith little ecological impact.


Growth form: Biennial or short-livedperennial forb.

Flower:Flowering heads aresolitary at the ends ofbranches. The floralbracts are stiff and tippedwith a dark, comb-likefringe that gives a spottedappearance. The flowers arepinkish purple or, rarely,cream coloured.

Seeds/Fruit: Seeds have a tuftof persistent bristles.

Leaves: Rosette leaves are up to15 cm long and deeply lobed. The principal stem leaves arepinnately divided, have smoothmargins, and become smallertoward the top of the shoot.Leaves are alternate.

Stems: Mature plants are 0.2–1.8 m tallwith one or more erect stems.

Roots: Spotted knapweed has a stouttaproot.

Seedling: Rosettes of spotted and diffuseknapweed are nearly indistinguishable. Leaves arenarrow and 1–2 times pinnately divided (Stubbendiecket al. 1995).

Similar Species

Exotics: Other knapweeds include diffuse knapweed(Centaurea diffusa), which has a distinct terminal spineon the floral bracts; Russian knapweed (Acroptilonrepens), whose flowers are smaller than those ofspotted knapweed and do not have black mottling onthe flower bracts; and squarrose (C. virgata var.squarrosa) and black (C. nigra) knapweeds.

Natives: None in Canada. Other native members of thesunflower family can resemble knapweed in theseedling/rosette stage.

Agricultural: Spotted knapweed reduces or displacesdesirable forage plant species and reduces carryingcapacity for livestock and wildlife (Sheley and Jacobs1997).

Ecological: Spotted knapweed is a highly competitiveweed that invades disturbed areas and degradesdesirable plant communities. It forms nearmonocultures in some areas of western North America,

including BC. Although spotted knapweed is usuallyfound in disturbed areas, it may invade adjacent areasthat are relatively undisturbed (Rutledge andMcLendon. Undated).

Human: Spotted knapweed can cause skin irritation.Hands and exposed skin should be washed with soapand water following contact with this plant.

SPOTTED KNAPWEED

Centaurea biebersteinii DC. Family: Asteraceae (Sunflower).

Other Scientific Names: Centaurea maculosa.




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General requirements: Spotted knapweed iswidespread at low- to mid-elevation grasslands and dryopen forests. It is commonly found on roadsides, fields,

and disturbed areas. It is adapted to well-drained, light-to coarse-textured soils but is intolerant to dense shade.It tends to inhabit moister habitats than diffuse

knapweed, preferring areas that receive 30–50 cmannual precipitation, but it can survive in very dryclimates such as those of Ashcroft and Osoyoos.

Distribution: Spotted knapweed is widely distributedthroughout North America. In the US, it is especiallyprevalent in Washington, Idaho, Montana, andWyoming (Sheley and Jacobs 1997). The weed isfrequent in southern BC east of the Coast-Cascademountains. It is regarded as a major concern in theKootenay, Okanagan, Thompson, Cariboo, Omineca,and Peace River agricultural reporting regions and ispresent on the Mainland and Vancouver Island.


Life cycle: Spotted knapweed is a perennial plant thatgerminates in spring or autumn. Seedlings develop intorosettes that usually persist for one growing seasonwhile the plant develops a root system (FEIS 1996).Plants usually bolt for the first time in the spring of thesecond growing season and flower from August throughSeptember, depending on elevation and latitude.Individual flowers bloom 2–6 days (FEIS 1996). Plantsare self-fertile and are also cross-pollinated by insects.


Seed production: This species is a prolific seedproducer, with individual plants producing up to140,000 seeds/m2 (Rutledge and McLendon. Undated).Most seeds are shed immediately after reachingmaturity.

Seed bank: Spotted knapweed seeds exhibit 3germination behaviours: dormant light-sensitive,dormant light-insensitive, and non-dormant (FEIS1996). Dormant seeds form a seed bank and mayremain viable in the soil for over 8 years (Rutledge andMcLendon. Undated). Roze (1981) found that theaverage density of spotted knapweed seeds in the seedbank from 4 sites in BC ranged from 620 to 5,628seeds/m2.

Dispersal: Spotted knapweed seeds usually shed in theimmediate area around the parent plant (Watson andRenney 1974). Seeds are often spread in hay and onvehicle undercarriages.


Biocontrol: Twelve biocontrol agents have beenreleased in the province for managing spottedknapweed: Agapeta zoegana (moth), Chaetorelliaacrolophi (fly), Cyphocleonus achates (weevil),Larinus minutus (weevil), Larinus obtusus (weevil),Metzneria paucipunctella (moth), Pelochristamedullana (moth), Puccinia jaceae (stem and leafrust), Sphenoptera jugoslavica (beetle), Terrellia virens(fly), Urophora affinis (fly), Urophora quadrifasciata(fly) (Powell et al. 1994). Currently, there is no singlebiological control agent that effectively manages thisweed. The most promising agents thus far are the root-feeding insects Agapeta zoegana and Cyphocleonusachates. Other species, such as the seed head weevils,Larinus minutus and Larinus obtusus, and the seedhead flies, Urophora affinis and Urophoraquadrifasciata, may be having an impact on seedproduction. Cattle and sheep will graze spottedknapweed, although sheep appear to be the moreeffective control animal. Olson et al. (1997) found thatsheep would graze on spotted knapweed rosettes andseedlings when associated grasses were dormant. Nosimilar work has been done in the province, however.

Mechanical: Cutting, mowing, or pulling spottedknapweed before the plant sets seed can be effective ona local basis for small populations. However, spottedknapweed seeds can remain dormant in the soil for

long periods, so follow-up treatments will be requiredto make sure the plant has been controlled. Attempt toremove the entire root system so the plant will not re-sprout from the crown or remaining roots.

Fire: The role of fire as an effective management toolis unclear. Watson and Renney (1974) report that it wasa successful control in Russia and grasses replaced it.No similar work has been conducted in the province.

Herbicides: Several herbicides are effective. Picloramhas been most effective but persists in the soil and candamage non-target species (Harris and Cranston 1979;Watson and Renney 1974). Other effective herbicidessuch as dicamba, 2,4-D, clopyralid, and glyphosate arealso effective (Beck 1997). On suitable terrain thesecan be broadcast-applied, but a backpack sprayer orwick may be more appropriate on small areas tominimize damage to non-target plants. Herbicidesshould be applied before the mature plants set seed tomaximize effectiveness. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Prevent the establishment of newinfestations by minimizing disturbance and seeddispersal. Seed all disturbed sites to provide soil coverand competition with weeds.


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160

Beck, K. G. 1997. Diffuse and spotted knapweed.Colorado State University Cooperative ExtensionNatural Resource Series, No. 3. 110.http://www.ext.colostate.edu/pubs/natres/03110.html[24 Jan 00].

Davis, E. S. 1990. Spotted knapweed (Centaureamaculosa) seed longevity, chemical control and seedmorphology. MS thesis. Montana State University,Bozeman.

FEIS—Fire Effects Information System. 1996.Prescribed Fire and Fire Effects Research Work Unit,Rocky Mountain Research Station (producer), US ForestService. http://www.fs.fed.us/database/feis/ [12 Mar 98].

Fletcher, R. A., and A. J. Renney. 1963. A growthinhibitor found in Centaurea sp. Canadian Journal ofPlant Science 43: 475–481.

Harris, P., and R. Cranston. 1979. An economicevaluation of control methods for diffuse and spottedknapweed in western Canada. Canadian Journal ofPlant Science 59: 375–382.

Lacey, C. A., J. R. Lacey, P. K. Fay, J. M. Stry, and D.L. Zamora. 1995. Controlling spotted knapweed inMontana rangeland. Circular 311. Bozeman: MontanaState University Cooperative Extension.

Lacey, J. R., C. B. Marlow, and J. R. Lane. 1989.Influence of spotted knapweed (Centaurea maculosa)on surface water runoff and sediment yield. WeedTechnology 3: 627–631.

Mauer, T., M. J. Russo, and M. Evans. 1998. Elementstewardship abstract for Centaurea maculosa. TheNature Conservancy, Wildland Weeds Management andResearch Program.

http://tncweeds.ucdavis.edu/esadocs/documnts/centmac.html [28 Jul 98].

Olson, B. E., R. T. Wallender, and J. R. Lacey. 1997.Effects of sheep grazing on a spotted knapweedinfested Idaho fescue community. Journal of RangeManagement 50: 386–390.


Roze, L. D. 1981. The biological control of Centaureadiffusa Lam. and C. maculosa Lam. by Urophoraaffinis Frauenfeld and U. quadrifasciata Meigan(Diptera: Tephritidae). Ph.D. thesis. University ofBritish Columbia.


Sheley, R. L., and J. S. Jacobs. 1997. “Acceptable”levels of spotted knapweed (Centaurea maculosa)control. Weed Technology 11: 363–368.

Stubbendieck, J., G. Y. Friisoe, and M. R. Bolick.1995. Spotted knapweed. Weeds of Nebraska and theGreat Plains. Lincoln: Nebraska Department ofAgriculture, Bureau of Plant Industry.

References __________________________________________

Integrated Management Summary Spotted knapweed can spread readily by stemsthat are carried on vehicles or in infested hayor seed. Early detection and prompt control ofsmall infestations are the best ways to managethis weed. Spotted and diffuse knapweed canbe managed similarly (Beck 1997). They arereadily controlled with herbicides but will re-invade unless cultural techniques are used(Beck 1997). Sheley and Jacobs (1997) foundthat a 90% reduction in diffuse knapweed wasnecessary to shift the competitive relationshipin favour of bluebunch wheat grass.


161

Watson, A. K., and A. J. Renney. 1974. The biology ofCanadian weeds. 6. Centaurea diffusa and C.maculosa. Canadian Journal of Plant Science 54:687–701.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Spotted knapweed. Weeds of the West. Western Societyof Weed Science, in cooperation with the WesternUnited States Land Grant Universities CooperativeExtension Services, Newark, CA.



Flower: Flower heads are small, numerous,and have 4–8 rose- or pink-coloured

flowers. The flower bract tips are spreading, with theterminal spine longer than thelateral spines on each bract.

Seeds/Fruit: No informationavailable.

Leaves: Lower leaves aredeeply dissected, upperleaves are bract-like.

Stems: Mature plants aretypically 30–45 cm tall withhighly branched stems.

Roots: Taproot.

Seedling: Seedlings have deeply indented, grey-greenleaves.

Similar Species

Exotics: Often confused with diffuse knapweed(Centaurea diffusa), but a true perennial, and bracts arerecurved. Unlike diffuse knapweed, seed heads aredeciduous, falling off the stems soon after seedsmature.


Agricultural: Can reduce forage production potentialfor livestock and wildlife.

Ecological: A highly competitive weed that can

displace native rangeland plants. This species is welladapted to dry disturbed areas.


SQUARROSE KNAPWEED

Centaurea virgata Lam. var. squarrosa(Willd.) Boiss.Family: Asteraceae (Sunflower).





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General requirements: Squarrose knapweed isgenerally found on light, dry, porous soils. It appearsbest adapted to open habitats. It is rare on cultivatedlands and irrigated pasture in the US because it cannottolerate cultivation or excessive moisture.

Distribution: Not present in BC. In the US, squarroseknapweed is found on plains, rangelands, and forestedbenchlands and is currently established in California,Utah, Oregon, and Washington.


Life cycle: Perennial forb. Squarrose knapweed mayremain as a rosette for several years before it bolts andproduces seeds (Roche and Roche 1991). Once it has

matured, it can continue to flower and produce seedsfor several years. Squarrose knapweed flowers fromJune through August. Seed heads are deciduous andfall off the stems soon after seeds mature.


Seed production: Each seed head produces 3–4 seeds.

Seed bank: Seeds may remain viable in the soil forseveral years.

Dispersal: The seed heads readily attach to animal furand vehicle tires.


No illustration available.

Very similar in appearance to

diffuse knapweed.

Beck, K. G. 1997. Diffuse and spotted knapweed.Colorado State University Cooperative ExtensionNatural Resource Series, No. 3. 110.http://www.ext.colostate.edu/pubs/natres/03110.html[24 Jan 00].

Roche, B. F., Jr., and C. T. Roche. 1991. Identification,introduction, distribution, ecology, and economics ofCentaurea species. In L. F. James, J. O. Evans, M. H.Ralphs, and R. D. Child, eds. Noxious Range Weeds.Boulder, CO: Westview Press.

Roche, C. T. 1999. Squarrose knapweed. In R. L.Sheley and J. K. Petroff, eds. Biology and Managementof Noxious Rangeland Weeds. Corvallis: Oregon StateUniversity Press.

Watson, A. K., and A. J. Renney. 1974. The biology ofCanadian weeds. 6. Centaurea diffusa and C.maculosa. Canadian Journal of Plant Science 54:687–701.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Squarrose knapweed. Weeds of the West. WesternSociety of Weed Science, in cooperation with theWestern United States Land Grant UniversitiesCooperative Extension Services, Newark, CA.

Youtie, B. 1997. Weed control as the first step inprotecting and restoring native plant communities onnortheast Oregon natural areas. Conservation andManagement of Native Plants and Fungi. Corvallis:Native Plant Society of Oregon.

Biocontrol: Urophora affinis (fly) and Urophoraquadrifasciata (fly), which attack spotted (Centaureamaculosa) and diffuse knapweed (C. diffusa), willapparently use this species as an alternate host.However, there is no information indicating that theseinsects have any impact on the plant.

Mechanical: Cutting, mowing, and removing the plantbefore it sets can reduce seed production, but it is notlikely to eliminate the infestation. A program withcutting and mowing over several years will typically berequired for long-term management.

Fire: Burning is not recommended for managingsquarrose knapweed. Roche (1999) reported that thisspecies will increase when fire is applied to dryrangeland sites.

Herbicides: Picloram, clopyralid, dicamba, andglyphosate all have been effective management agents(Beck 1997; Youtie 1997; Watson and Renney 1974).Herbicides should be applied before the mature plants

set seed to maximize effectiveness, but autumnapplication to newly re-sprouted basal leaves can alsobe effective (Roche 1999). Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Prevent establishment of newinfestations. Manage land use to maintain vigorousnative communities.


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Integrated Management SummaryThis species does not occur in the province andshould be a priority for immediate eradicationif it is found.


Growth form: Winter annual or biennialforb.

Flower: Flowers are inan umbrella-like cluster at theend of long, slenderstalks arising fromthe leaf axils.Flowers are purplishpink and generallyborne in clusters of 2or more (Whitson etal. 1996). Thepersistent styles of thisplant are 2.5–5.0 cm longand coil together atmaturity, enveloping the fruitat the base.

Seeds/Fruit: Fruits are 5-lobed and long-beaked, witheach lobe splitting away at maturity.

Leaves: The leaves of young plants form a basalrosette. Older leaves grow up to 30 cm long and aredivided into narrow, feather-like lobed or toothedsegments. Both leaves and stems are hairy.

Stems: Mature plants have decumbent to erect stemsthat are 3–40 cm long.

Roots: The slender taproot is about 8 cm long, andthere are secondary fibrous roots.


Similar Species



Agricultural: Can compete with agricultural crops formoisture and nutrients. It may also cause livestockpoisoning and is an alternate host for beet curly top,peach yellow bud mosaic, and strawberry green petal,among other plant diseases (Royer and Dickinson1999).

Ecological: An annual, winter annual, or biennial thatcan quickly invade disturbed sites.


STORK’S-BILL

Erodium cicutarium (L.) L’Her.Family: Geraniaceae (Geranium).


Other Common Names: Redstem filaree, cranesbill, cutleaf filaree.



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General requirements: In BC, grows from low- tomid-elevations in moist to dry fields, woodlands, anddisturbed habitats on well-drained, clayey, loamy, orsandy soil. It will tolerate a broad range of climates andcan grow in areas that experience harsh, snowy wintersbecause its short growing season allows it to completeits life cycle before the onset of freezing weather (FEIS1996). It will tolerate partial shade, but plant vigour isreduced.

Distribution: Common in southwestern and south-central BC (Douglas et al. 1999) and throughout NorthAmerica. Reported from all agricultural reportingregions except the Omineca but is not considered amajor concern anywhere in the province.

Historical: Introduced from Europe, perhaps as earlyas the 1700s by Spanish explorers (FEIS 1996).

Life cycle: Plants often germinate in the autumn and

develop leaves. The following spring the plant resumesgrowth and flowers in the spring. Seeds ripen fromMay to June, depending on geographic location.



Seed bank: Seeds can remain viable for many years(FEIS 1996).

Dispersal: When moist, the coiled styles envelopingthe seed expand, uncoil, and drive the arrow-shapedfruit into the ground.



Ehlhardt, M. H., and W. F. Stracham. 1993. Orchardand vineyard weed control with glufosinate. WesternSociety of Weed Science 46: 44–45.



Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Redstem filaree. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: None.

Mechanical: Mowing or burning before seed-set caneliminate seed production.

Fire: (See above.)

Herbicides: Can be controlled with late autumn orearly spring applications of 2,4-D or dicamba torosettes, but it is tolerant of glufosinate (Ehlhardt andStracham 1993). Consult the most recent edition of BCMinistry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Minimize disturbance, eliminateseed production and dispersal, and maintain vigorousperennial plant communities.


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References __________________________________________

Integrated Management SummaryIntegrated management should focus onreducing or eliminating seed production anddepleting the seed bank. Combine herbicide ormechanical methods to remove rosettes andremove seed heads from flowering plants. Seeddisturbed areas to perennial grasses and managelivestock to minimize disturbance and maintainvigorous perennial plant communities.



Flower: Flowersare 2 cm in

diameter, bright yellow,numerous in flat-toppedclusters. Flowers have 5separate petals that are twiceas long as the sepals. Stamensare numerous and paired into3 groups.

Seeds/Fruit: Seed pods are 6mm long, rust-brown, with 3-celled capsules that containnumerous seeds (Whitson et al.1996).

Leaves: Leaves are opposite, 1–3 cm long, oval-shaped, with prominent veins and covered withtransparent dots.

Stems: Mature plants are0.1–1.0 m high. The stems areerect, 2-sided, rust coloured,with numerous branches.

Roots: Short rhizomes.


Similar Species



Agricultural: St. John’s-wort invades grazed anddisturbed lands. In dense stands, it displaces nativeplant species and reduces livestock and wildlife forage.The plant also contains a toxin that causes skin

irritation and blistering in light-coloured livestockwhen they are exposed to sunlight (Powell et al. 1994).


Human: Commercially available as an antidepressant.

ST. JOHN’S-WORT

Hypericum perforatum L.Family: Clusiaceae (St. John’s-wort).


Other Common Names: Klamath weed, goatweed.



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General requirements: In BC, St. John’s-wort growsat low- to mid-elevations in coastal, grassland, andopen forested regions. It is commonly found onrangeland, pasture, and meadows and along roadsidesand disturbed areas. It is best adapted to dry, gravelly,or sandy soils and can tolerate pH ranges of 4.3–7.6(Rutledge and McLendon. Undated).

Distribution: St. John’s-wort occurs in scatteredpockets in the Kootenays, Okanagan, Boundary, NorthThompson, Cariboo, Skeena, Fraser Valley, andVancouver Island areas. It is not present in the PeaceRiver area. It is common throughout the US PacificNorthwest (Powell et al. 1994).


Life cycle: St. John’s-wort grows early in spring whensoil moisture is available, and flowers from June toSeptember, depending on geographic location. Its deeproot system is capable of supporting the plant when thewater available to other species has been depleted(Crompton et al. 1988).

Mode of reproduction: By seed and vegetatively fromroots. The root system spreads laterally and is capableof forming new buds that separate from the parent(Rutledge and McLendon. Undated).

Seed production: It produces 15,000–30,000seeds/plant.

Seed bank: Seeds may remain viable in the soil 6–10years.

Dispersal: Seeds have a gelatinous coat that facilitateslong-distance dispersal.


Crompton, C. W., I. V. Hall, K. I. N. Jensen, and P. D.Hilderband. 1988. The biology of Canadian weeds. 83.Hypericum perforatum L. Canadian Journal of PlantScience 68: 149–162.

Piper, G. L. 1999. St. Johnswort. In R. L. Sheley and J.K. Petroff, eds. Biology and Management of NoxiousRangeland Weeds. Corvallis: Oregon State UniversityPress.


Rees, N. E., P. C. Quimby, Jr., G. L. Piper, E. M.Coombs, C. E. Turner, N. R. Spencer, and L. V.Knutson (eds). 1996. Biological Management of Weedsin the West. Western Society of Weed Science, incooperation with USDA Agricultural Research Service,Montana Department of Agriculture, and MontanaState University.


Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996. St.John’s-–wort. Weeds of the West. Western Society ofWeed Science, in cooperation with the Western UnitedStates Land Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: Chrysolina hyperici (beetle) andChrysolina quadrigemina (beetle) have been releasedin the province (Powell et al. 1994) and have continuedto produce sustainable populations on the weed,although the insect needs to be moved to newpopulations periodically. Agrilus hyperici (beetle),Aplocera plagiata (moth), and Aphis chloris (aphid)have also been released in the province.

Mechanical: Can be managed by tillage in agriculturalfields.


Herbicides: Combinations of 2,4-D and picloram, or2,4-D and glyphosate have successfully managed thisweed in the US (Rutledge and McLendon. Undated).Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applying


Cultural/Preventive: Maintain plant communitiesdominated by perennial grasses and forbs (Piper 1999).


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References __________________________________________

Integrated Management SummarySt. John’s-wort is considered to be undersuccessful biological control throughout theprovince. For small infestations, herbicide useand seeding disturbed areas are likely the bestcombination initially. Manage grazing animalsto maintain dense stands of perennial species.



Flower: Flowers arelight-yellow (sulphur

coloured) with 5 petals.

Seeds/Fruit: Each flower producesnumerous small seeds (1 mm) that areslightly flattened.

Leaves: Leaves are alternate, palmatelycompound with 5–7 toothed leaflets oneach leaf. Leaf stalks have conspicuousperpendicular hairs, and leaves appeargreen on the underside.

Stems: Mature plants are 30–70 cm tall,with one to several stems growing from well-developed rootstocks (Whitson et al. 1996).

Roots: Fibrous roots and lateral rhizomes.


Similar Species

Twenty-seven species ofPotentilla are found in BC(Douglas et al. 2000). Floralcharacteristics, arrangementsof leaves and leaflets, and thetype and arrangement of hairs areimportant features to consider whenidentifying cinquefoil.

Agricultural: Unpalatable to grazing animals. It is alsovery competitive with native plants and reduces foragefor livestock and wildlife on rangelands (Rice 1999).

Ecological: A competitive, early successional speciesthat can dominate sites and displace native plant

species in both disturbed and undisturbed habits. Itmay also alter ecosystem function, although this hasnot been verified scientifically (Powell 1996).


SULPHUR CINQUEFOIL

Potentilla recta L.Family: Rosaceae (Rose).


Other Common Names: Rough-fruited cinquefoil.

Legal Status: Regional Noxious: Columbia-Shuswap, NorthOkanagan, Okanagan-Similkameen, Thompson-Nicola.


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Impacts ____________________________________________


General requirements: Sulphur cinquefoil is apioneer species found in habitats from early successionto relatively dense forest overstorey, but the plantappears intolerant of complete shade (Powell 1996). Itappears adapted to a wide range of soils and climates,but currently it is mostly restricted to the grasslandsand dry forest zones in BC (Powell 1996).

Distribution: Naturalized throughout much of NorthAmerica, occupying dry to moist habitats, roadsides,pastures, overgrazed rangelands, and disturbed areas(Douglas et al. 1999). Common in southern British

Columbia, especially in the Douglas fir zone (Powell1996). Considered a major concern in the Kootenay,Okanagan, and Thompson agricultural reportingregions.


Life cycle: A long-lived perennial. Plants germinate inspring and establish a woody taproot. Plants can liveup to 20 years, but the central core of the taprootslowly rots away and the plant gives out to otherspecies. In southern parts of the province, flowering

occurs from June to late July and seeds are set in Julyand August. Herbaceous material dries in August toend the life cycle (Powell 1996).


Seed production: Some plants produce 1,650 seeds(Powell 1966).

Seed bank: Seed survival may be short, not exceeding2 years (Powell 1996).

Dispersal: Seeds can be dispersed by birds, smallmammals, ungulates, and other grazing animals, eitherthrough digestion or by being picked up and moved onhooves or in hair. Seeds can also be dispersed in cuthay and bedding material (Powell 1996).


BC Ministry of Agriculture, Food and Fisheries.Undated. Integrated Weed Management: SulphurCinquefoil—Pastures and Rangeland. Fact Sheet.

Douglas, G. W., D. Meidinger, and J. Pojar, eds. 1999.Illustrated Flora of British Columbia. Vol. 4:Dicotyledons (Orobanchaceae through Rubiaceae).Province of British Columbia.

Duncan, C. L. 1993. Chemical control of sulfurcinquefoil on range and pasture. Proceedings of theMontana Weed Control Association. Clanay, MT.


Powell, G. 1996. Analysis of sulphur cinquefoil inBritish Columbia. Research Branch, BC Ministry ofForests, Victoria. Working Paper 16.

Rice, P. 1999. Sulfur cinquefoil. In R. L. Sheley and J.K. Petroff, eds. Biology and Management of NoxiousRangeland Weeds. Corvallis: Oregon State UniversityPress.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Sulfur cinquefoil. Weeds of the West. Western Societyof Weed Science, in cooperation with the WesternUnited States Land Grant Universities CooperativeExtension Services, Newark, CA.

Biocontrol: None. Preliminary screening work iscurrently being conducted.

Mechanical: Small infestations can be managed byhand-digging.


Herbicides: Picloram, clopyralid, and 2,4-D have beeneffective in the US. Picloram and, to a lesser extent,glyphosate have been used for management in BC.Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: It does not survive cultivationwell.


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References __________________________________________

Integrated Management SummaryIntegrated management should focus onprevention of new infestations through grazingmanagement and maintaining vigorousperennial plant communities. Cultural controls,such as hand-pulling, can be effective on newinfestations but should be followed up toensure that the plant has been eradicated. Seeddisturbed areas to perennial grasses to providecompetition. Use appropriate herbicides forlarger infestations, along with othermanagement techniques.


Growth form: Biennial or short-livedperennial.

Flower: Several to many daisy-like, brightyellow flowers in flat-topped clusters. The black-tippedbracts of the flower heads are arranged in a single row.Plants flower from July throughSeptember, depending ongeographic location.

Seeds/Fruit: Ribbed seedsare 1 mm long with apappus of white hairsabout 3 mm long.

Leaves: Basal leavesare stalked, 4–20 cmlong, and 2–6 cm wide.Stem leaves are alternate,becoming progressivelysmaller and stalklessmoving upward. All leaves aredeeply cut, giving the plant aragged appearance

Stems: Mature plants are 0.2–1.2 m tall. The one toseveral stems are erect and are branched near the top.

Roots: A poorly developed to evident taproot withwell-developed fibrous roots.

Seedling: The first 2–3 leaves are roundedwith small teeth on the margin, but laterleaves are deeply lobed. Star-shapedhairs are present on the first to fourthleaf stage but are later hairless (Royerand Dickinson 1999).

Similar SpeciesExotics: The leaves of common tansy (Tanacetumvulgare) are sharply toothed, and the flowers look likeyellow buttons because the ray flowers are absent.

Natives: Dryland ragout (Seneca eremophilus)resembles tansy ragwort, but the leaf tips are pointedrather than rounded.

Agricultural: Tansy ragwort reduces forage productionof pastures by up to 50% (BC Ministry of Agriculture,Food and Fisheries. Undated). Contains alkaloids thatcan poison livestock, but the plant is often avoided.Animals can be affected through contaminated hay orsilage. Cattle and horses should not be grazed onpastures with more than 5% cover of tansy ragwort.

Ecological: Primarily a weed on agricultural land buthas been appearing on coastal clear-cuts in BC(Douglas et al. 1998).

Human: Trace amounts of alkaloids appear in milkand honey produced from infested pastures, raisingconcerns for human consumption of these products.

TANSY RAGWORT

Senecio jacobaea L.Family: Asteraceae (Sunflower).


Other Common Names: Common ragwort.



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Impacts ____________________________________________


General requirements: Grows on disturbed sites inpastures, hayfields, roadsides, and clear-cuts.

Distribution: Frequent and considered a major concernin the Lower Mainland and southern Vancouver Island

agricultural reporting regions; also present in theOkanagan. Found in the Atlantic provinces and Ontario(Frankton and Mulligan 1970).


Life cycle: A low-growing rosette is produced in thefirst year. Flower-bearing stems are produced in thesecond, and often subsequent, years. Seeds germinatein both spring and autumn, forming new rosettes.


Seed production: One plant can produce more than150,000 seeds.

Seed bank: Seeds can remain dormant 4–5 years andremain viable over 20 years.

Dispersal: Primarily by wind, water, and animals.


BC Ministry of Agriculture, Food and Fisheries.Undated. Tansy Ragwort in British Columbia. FactSheet.




Biocontrol: Five agents have been released in BC:Tyria jacobaeae (moth), Botanophila seneciella (fly),Longitarsus flavicornis (beetle), Longitarsus jacobaeae(beetle), and Cochylis atricapitana (moth). In BC, thecinnabar moth (Tyria) causes localized defoliation butfails to provide long-term control. Longitarsusjacobaeae has resulted in localized control, particularlyin combination with the root-boring Cochylis moth.

Mechanical: Seed production can be prevented byrepeated mowing before flowering is advanced. Plantsmown after flowering can still set seed. Smallinfestations can be pulled by hand.


Herbicides: Spring or mid-autumn applications of 2,4-D are effective at managing young seedlings androsettes. Dicamba, or a combination of dicamba and2,4-D, is effective at more advanced growth stages.Consult the most recent edition of BC Ministry ofAgriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applying


Cultural/Preventive: Seed disturbed areas to perennialgrasses and forbs. Manage grazing animals to maintainperennial plant communities. Hand-pull plants andremove them from new infestations. Cut plants beforethey go to seed.


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References __________________________________________

Integrated Management SummaryCultural, mechanical, chemical, and biologicalcontrol methods are all possible. Use culturaland mechanical methods on small infestations.Apply herbicides to manage medium-sizedpopulations, and use biocontrol for largeinfestations where it is impractical to use othermanagement methods. Plants must be cut priorto formation of the easily wind-blown seeds.



Flower:Greenish,

small flowers areclustered at leaf axilsand stem tips. Petalsare absent; insteadthere are 5 petal-likesepals.

Seeds/Fruit: Eachflower produces a single,wrinkled, 3-angled seedthat protrudes fromthe sepals.

Leaves: Lightgreen, heart-shapedleaves are 3–10 cmlong and have wide-spreading basal lobes.

Leaves are alternate and stalked and have paper sheathswhere the stalk joins the stem.

Stems: Erect, green stems to 1.0 m.

Roots: Taproot.

Seedling: Cotyledons are round with stalks and arenotched at the base. First leaves are triangular withrounded basal lobes and a papery sheath at the base ofthe leaves (Royer and Dickinson 1999).

Similar Species

Exotics: Buckwheat (Fagopyrum esculentum) hasreddish stems, larger white or reddish flowers, andsmooth fruit (Frankton and Mulligan 1970).

Natives: Wild buckwheat (Polygonum convolvulus) isa twining or prostrate plant whose seeds do notprotrude from the sepals (Frankton and Mulligan1970).

Agricultural: A serious weed of cereal and oilseedcrops, tartary buckwheat reduces crop yields by asmuch as 70% and lowers crop quality. Seeds aredifficult to remove from grains, reducing grain qualityand increasing dockage and cleaning costs (Sharma1986). Heavily contaminated grains cannot be used forflour, rolled oats, or malting processes (Royer andDickinson 1999). Infestations can occur in pastures andforage seedings. Pigs and other livestock can suffer

severe skin inflammation after eating large quantitiesof this species and being exposed to sunlight.

Ecological: Occurs in roadsides and other disturbedhabitats but is not likely to invade perennial nativecommunities.

Human: Used for livestock feed, as a green manurecrop, and as a soil renovator (Sharma 1986).

TARTARY BUCKWHEAT

Fagopyrum tataricum (L.) Gaertn.Family: Polygonaceae (Buckwheat).


Other Common Names: Tartarian buckwheat, sarrasin.



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General requirements: Well adapted to relativelymoist and cool weather but is susceptible to frost inspring or autumn. It tolerates a wide range of soilconditions but appears best adapted to well-drained

soils; most competitive on low-fertility soils.

Distribution: In BC it grows in cereal and oilseedcrops, forage crops, roadsides, and disturbed areas.


Impacts ____________________________________________

This plant is only found in the Peace River agriculturalreporting area, where it is regarded as a major concern.Found throughout the US and Canada and is asignificant concern in north-central Alberta and west-central Manitoba (Royer and Dickinson 1999).

Historical: Introduced from Asia as a cultivated crop.

Life cycle: Plants overwinter as seed. Most seedsgerminate in spring, but some germination occursthroughout the growing season. Mature seeds areproduced 60–80 days after emergence. Tartarybuckwheat flowers indeterminately, so flowers,immature seeds, and mature seeds may all be present atone time. One generation per year is produced (Sharma1986).


Seed production: A single plant can produce400–1,100 seeds, depending mainly on the size of theindividual plant.

Seed bank: Fresh seeds require after-ripening togerminate. The period of after-ripening depends onenvironmental conditions and occurs fastest underwarm, dry conditions. Soils are likely to contain seedsat all stages from dormant to fully after-ripened(Sharma 1986)

Dispersal: Some seeds are shed and scattered beforeharvest, but many seeds are harvested with the cropand contaminate the seed. Machinery can locallydisperse seeds, but contaminated seed is the mainsource of long-distance movement.




Sharma, M. P. 1986. The biology of Canadian weeds.74. Fagopyrum tataricum (L.) Gaetn. CanadianJournal of Plant Science 66: 381–393.

Biocontrol: None.

Mechanical: Cultivation kills seedlings, so practicessuch as delayed seeding, autumn and spring tillage,summerfallowing, and post-seeding cultivation areeffective control methods. Shallow autumn tillage canresult in a flush of emerging seedlings that will bekilled by frost, if post-harvest weather conditions arewarm and dry enough to allow seed after-ripening.Mowing before seed-set will prevent seed production.


Herbicides: Tartary buckwheat is susceptible to manyherbicides. Dicamba, dicamba mixes, and 2,4-D havebeen effective on pastures and rangelands when weedsare actively growing. Consult the most recent edition ofBC Ministry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Fall-seeded crops can reduceinfestations through competition and by stimulatingautumn emergence of weed seedlings that cannotsurvive the winter.


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References __________________________________________

Integrated Management SummaryA combination of tillage, seeding, andherbicides appears to be the best approach tointegrated management of this species. Foragecrops used in a rotation also may controltartary buckwheat. Fertilizers containingphosphorous can improve crop yield at theexpense of tartary buckwheat, but the fertilizermust be placed near the crop seed.



Flower: Yellow toyellow-orange

5-petalled flowers areborne on stalks arisingfrom the leaf axils.

Seeds/Fruit: Fruitsare rounded with9–15 segmentsarranged in a disk,each containingnumerous grey-brownseeds.

Leaves: Leaves are alternate,heart-shaped, pointed at theend, 10–20 cm wide, andattached on slender stems

(Whitson et al. 1996). Leaves remain perpendicular tothe sun all day (Duyssen 1997).

Stems: Mature plants are 1–2 m tall. Stems are erectand branched, and the entire plant is covered withshort, soft, “velvety” hairs.

Roots: Taproot.

Seedling: The seed leaves (cotyledons) have slightlydifferent shapes: one is nearly round, the other moreheart-shaped. Both cotyledon margins are entire, andcotyledons are covered on both surfaces with shorthairs (Carey et al. 1993).

Similar Species



Agricultural: A serious problem in croplands in NorthAmerica because of its high seedling vigour, rapidgrowth habit, tolerance to many herbicides, and abilityto produce large amounts of seed (Starke and Renner1996). It is often a pest in corn, sorghum, milo, andspring wheat (Duyssen 1997). Seeds can contaminatechicken feed and reduce the salability of eggs (Duyssen1997).

Ecological: The plant is able to produce large amountsof seed that remain viable for many years, and it is asuccessful seed producer even under competition. Theroots also exude a chemical that inhibits fungal growth.


VELVETLEAF

Abutilon theophrasti MedicFamily: Malvaceae (Mallow).


Other Common Names: Velvetweed, piemaker, elephant-ear,Indian mallow.



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Impacts ________________________________________


General requirements: In BC, velvetleaf occurs onlyat low elevations. It is commonly found in cultivatedfields, gardens, fencelines, and disturbed areas. It welladapted to sunny areas with rich soils.

Distribution: Widespread throughout North America.It occurs infrequently in southwestern BC and isknown only from the Lower Fraser Valley (Douglas et

al. 1999), where it is a potential threat to agriculturalproduction, particularly corn.

Historical: Introduced from either China or India forcommercial fiber production. It is believed that theentire North American population is derived from asingle plant (Duyssen 1997).

Life cycle: Flowering occurs from late June throughOctober. Seeds may germinate throughout the growingseason. Seeds have a hard coat that contains bacteriaand tannin-like compounds to protect it from infection(Duyssen 1997).


Seed production: A single plant may produce700–1,700 seeds (Duyssen 1997).

Seed bank: Seeds retain their viability in the soil forover 50 years, making eradication difficult (Whitson etal. 1996). If infestations are allowed to persist andestablish a seed bank, this weed can be troublesome.





Duyssen, K. 1997. Velvetweed (velvetleaf)contamination of corn screenings.http://www.ansci.cornell.edu/courses/as625/1997term/Kate/velvetwe.htm [10 Feb 99].

Starke, R. J., and K. A. Renner. 1996. Velvetleaf(Abutilon theophrasti) and sugarbeet (Beta vulgaris)response to trisulfuron and desmedipham plusphenmedipham. Weed Technology 10: 121–126.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Velvetleaf. Weeds of the West. Western Society of WeedScience, in cooperation with the Western United StatesLand Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: None.

Mechanical: Cutting or mowing plants after floweringbut before seed-set should eliminate the current yearseed production.


Herbicides: In non-crop situations, glyphosate,picloram, 2,4-D, and dicamba been used post-emergence to control velvetleaf. Herbicides should beapplied before seed-set. Consult the most recent editionof BC Ministry of Agriculture, Food and FisheriesCrop Production Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.Cultural/Preventive: Infestations can be difficult toeradicate because of the long viability of seeds in thesoil. Tillage can be effective in reducing seedling

emergence if the seeds are buried at least 7.5 cm in thesoil. Prevent the establishment of new infestations byminimizing disturbance, eliminating seed productionand dispersal, and maintaining vigorous perennialnative communities.


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References __________________________________________

Integrated Management SummaryVelvetleaf is usually not a problem onrangeland or forestland in BC. If this plant isfound, eliminate seed production until the soilseed bank has been depleted. Cut, pull, or treatplants with herbicide before they set seed.

Growth form: Perennial forb.Flower: Flower headscomprise several to many

small, compact clusters formingseveral compound umbels. Flowers rangefrom white to greenish; involucral bracts aremostly lacking (Douglas et al. 1998).

Seeds/Fruit: Egg-shaped, 2–4 mm long,smooth, glabrous, corky-thickened; ribs notequal, with a narrow raised border on edge ofdark intervals (Douglas et al. 1998).

Leaves: Basal and stem leaves divided 1–3 times,leaflets 3–4 times as long as broad, lance-shaped tonarrowly oblong or elliptical, sharply pointed andtoothed, 4–7 mm long; lateral veins ending at base ofthe teeth (Douglas et al. 1998).

Stems: Solitary or in a cluster, from atuberous-thickened and chambered base; leafy,glabrous, 0.5–2.0 m tall. Stems hollow, streaked withpurple. The somewhatswollen base with cavitiesseparated by crosspartitions of solid tissueis easily seen when thestem is split lengthwiseat the base just abovethe roots.

Roots: Taproot or clustersof tuberous roots around thestem base; chambered.Chambers contain thehighly toxic yellowish,oily exudate, cicutoxin.USE EXTREMECAUTION when cross-sectioning the roots.

Seedling: Seedling leaves are fern-like in appearance.

Similar Species

Exotics: Poison hemlock (Conium maculatum), whichis similar in appearance and highly poisonous, islocally common in the Vancouver and Victoria areasand rare in south-central BC (Douglas et al. 1998).Differs from water hemlock by having fern-like leavesthat give the plant a lacy appearance compared to waterhemlock, where the leaflets are 3–4 times as long asbroad. Fruits of water hemlock also have a narrowraised border, whereas the fruits on poison hemlock areegg-shaped, flattened, and smooth.

Natives: There are 4 native Cicuta species in BC andall are highly poisonous. Spotted cowbane (Cicutamaculata) is common throughout BC and differs fromwater hemlock in its much narrower leaves and notablespots on the stems. Bulbous water hemlock (Cicutahulbifera L.), which is infrequent east of the CascadeMountains (Douglas et al. 1998), is readily recognizedby the small bulblets that grow at the angles formed byleaf and stem (Frankton and Mulligan 1970). Europeanwater hemlock is rare in northeastern BC. Waterhemlock is also similar to hemlock water-parsnip (Siumsuave), which occupies similar habitats and has thesame distribution as spotted cowbane. Hemlock water-parsnip is not poisonous; its roots are solid; theinflorescence has bractlets; and the leaves are oncedivided, with each leaflet being linear and growing upto 10 cm long. Water hemlock roots are chambered, theinflorescence is bractless, and the leaflets are divided(Douglas et al 1998).

WATER HEMLOCK

Cicuta douglasii (DC.) Coult. & RoseFamily: Apiaceae (Parsley).


Other Common Names: Douglas’s water hemlock, Western waterhemlock.



176



Frankton, C., and G. A. Mulligan. 1970.Weeds of Canada. Publication 948.Ottawa: Canada Department ofAgriculture.

Agricultural: All water hemlocks are highly poisonousto livestock. A single root can kill a mature cow.

Ecological: Commonly grows in wet stream banks,ditches, marshes, meadows, and wet pastures.

Human: Water hemlock is a highly poisonous plantthat should be handled with care. All parts of the plantare poisonous to humans.

Biocontrol: None.

Mechanical: Water hemlock can be controlled bydigging, repeated mowing, and pulling. Care shouldbe taken to avoid contact with bare skin (wear latexor rubber gloves). Wash hands thoroughly afterhandling any part of this plant. Dispose of gloves andthoroughly clean any equipment used to control thisplant immediately after use.


Herbicides: No information available. Application ofherbicide will likely be restricted by proximity to waterand riparian areas. Consult the most recent edition ofBC Ministry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Prevent the establishment of newinfestations by removing plants, eliminating seed

production, and maintaining healthy nativecommunities. Fence infestations to restrict livestockaccess if practical.


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Impacts ____________________________________________

Management ________________________________________

References __________________________________________

Integrated Management SummaryThe tendency of this species to grow in wetareas may restrict the use of herbicides.Eliminate seed production and exhaust the soilseed bank by removing seed heads before seedsmature. Use latex or rubber gloves for hand-pulling, and avoid touching the plant with bareskin. Dispose of gloves after contact with theplant and thoroughly clean all equipment usedin handling this plant before subsequent use.

Habitat and Ecology __________________________________General requirements: Water hemlock is generallyfound on moist soils, can tolerate poorly drained soils,and is often scattered in riparian areas. It is usuallyfound along streams, irrigation ditches, and the bordersof marshes (Douglas et al 1998).

Distribution: In BC it is found in wet habitats east ofthe Coast-Cascade mountains and north to the Yukon(Douglas et al. 1998). It is present in all agriculturalreporting regions.

Historical: Native.

Life cycle: Douglas’s water hemlock is a biennial thatcan grow 3 m tall. In the first year, plants form a smallseedling that resembles wild carrot. Plants usually bolt

in the second year and produce numerous clusters ofwhite flowers. Plants flower from April through July.Seed-set begins in July and continues into winter. Mostseeds mature before dispersal and can germinateimmediately if environmental conditions arefavourable, but some seeds remain dormant.



Seed bank: No information available.Dispersal: By water and wind. Can also be spread bymachinery, on clothing, or in transported soil.


Growth form:Biennial or short-lived perennial forb.

Flower: The showy whiteflowers are fragrant andare arranged in open,spreading clusters witha few to many flowers.The flowers have 5notched petals that arelonger than the calyx.The sepals are fusedtogether to form asticky, tubular calyxsurrounding theflower. The plant haseither male or female flowers. In male plants the calyxis 15–22 mm long with 10 veins. In female plants thecalyx is 20–30 mm long, has 20 veins, and becomesinflated as fruit ripen. Plants flower from June toSeptember (Frankton and Mulligan 1970).

Seeds/Fruit: The capsules are egg-shaped, up to 20 mmlong with 10 teeth at the tip. The tiny, kidney-shapedseeds are bluish brown and are covered with warts.

Leaves: Basal leaves are lance-shaped, stalked, and2–10 cm long. The stem leaves are opposite, lance-shaped, and occur in 5–10 pairs. The lower pairs arestalked and often larger than the basal leaves, but they

become smaller and eventually without stalks higher onthe stem (Douglas et al. 1998).

Stems: The thick, almost woody base is branched witha few non-flowering shoots and several erect floweringshoots (McNeill 1977). The hairy stems grow 0.3–2.0m tall and have swollen nodes.

Roots: Initially a taproot, 5–40 cm deep, then thick,fleshy lateral roots develop and spread outward(McNeill 1977).

Seedling: Seedlings are yellowish green. The first pairof leaves is lance-shaped, and the second pair hasfinely toothed margins (Royer and Dickinson 1999).

Similar Species

Exotics: White cockle may be confused with night-flowering catchfly (Silene noctiflora) and red cockle(Silene dioica). Catchfly is an annual, produces maleand female flowers on a single plant, and has stickyhairs on its upper part. White cockle produces separatemale and female flowers, but catchfly has both sexes inthe same flower. Red cockle, which is rare in BC, hasdeep pink to red flowers.

Natives: A number of Silene are native to BC, andseveral of them are rare. Although all Silene have atubular flower and inflated calyx, most native specieshave male and female flowers on the same plant.

Agricultural: Mostly a problem in grain fields, alfalfaand clover crops, and pastures. White cockle seeds cancontaminate clover and forage seed.

Ecological: Occupies open sites such as roadsides anddisturbed places. It can rapidly colonize disturbed sitesand compete with native vegetation because of its high

rate of seed production. It is adapted to unshaded siteson well-drained, unsaturated soils. The seeds require along growing season for ripening, and its seedlings donot tolerate high temperatures (McNeill 1977).


WHITE COCKLE

Silene latifolia Poir. ssp. alba (P. Mill.) Greuter & BurdetFamily: Caryophyllaceae (Pink).

Other Scientific Names: Lychnis alba, Silene latifolia, Silene alba.

Other Common Names: White campion.



178

Impacts ____________________________________________


General requirements: Grows in cultivated crops(especially legume and grains), hayfields, fields,disturbed areas, railroads, and roadsides at low- to mid-elevations in BC on dry, well-aerated soils.

Distribution: Present in all agricultural reportingregions in the province and considered a major concernin the Peace River region. It is found across all ofsouthern Canada, especially in Ontario and Quebec, butless commonly in the Maritimes. It occurs throughoutthe northern US (McNeill 1977).


Life cycle: Plants can germinate, flower, and set seed in asingle season, but plants from later-germinating seedoverwinter as leaf rosettes on a well-developed root. Inspring, the erect stems emerge and the basal leaves wither.Over-wintered plants flower earliest, the most rapid

flowering and seed-set occurring during the longest days.

Mode of reproduction: Mostly from seed but root andstem fragments can establish.

Seed production: A single plant can produce over25,000 seeds/year (NS Department of Agriculture andFisheries 2001).

Seed bank: Some populations may require after anafter-ripening period. Seeds require light forgermination, and deeply buried seeds have pooremergence. Buried seeds remain viable, however, andgerminate well when brought to the surface.

Dispersal: Most seeds fall around the parent plant.White cockle seeds are similar to other clovers, so seedimpurities have been a source of dispersal.

Hybridization: Hybridizes with red campion (Silenedioica).



McNeill, J. 1977. The biology of Canadian weeds. 25.Silene alba (Miller) E.H.L. Krause. Canadian Journal

of Plant Science 57: 1103–1114.

NS Department of Agriculture and Fisheries. 2001.Nova Scotia Noxious Weeds—White Cockle.http://www.gov.ns.ca/nsaf/rir/weeds/white.htm[June 2001].

Royer, F., and R. Dickinson. 1999. Weeds ofCanada and the Northern United States.Edmonton: University of Alberta Press.

Biocontrol: None.

Mechanical: Over-wintering rosettes can be killedwith seed-bed preparation that buries the root-crownsor leaves them exposed to desiccate at the soil surface.Seeds are not adversely affected by cultivation. Duringthe growing season, tillage may spread the weedthrough regeneration of plant fragments. Mowing canreduce seed production, but to be effective many passesover the long flowering season may be required.

Fire: Fire is unlikely to affect populations of this plantbecause of its large seed bank.

Herbicides: White cockle is resistant to several commonherbicides, including 2,4-D, 2,4-DB, MCPA, and MCPB(McNeill 1977). Spring and early autumn applications ofdicamba provide some management (NS Department ofAgriculture and Fisheries 2001). Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Avoid using contaminated seed.New infestations should be promptly eradicated beforeseed-set by hand-pulling, tilling, or herbicides.


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References __________________________________________

Integrated Management SummaryWhite cockle is difficult to manage because ofits prolific seed production, long floweringseason, and resistance to herbicides. Preventionis the best approach, but once white cockle doesappear, it is necessary to prevent seedproduction through tillage, mowing, orherbicides. Management practices thatencourage competitive crop plants or perennialnative plant communities will help preventinvasion. Seed disturbed areas to perennialgrasses and forbs to provide ground cover andcompetition against this plant.


Growth form: Annual, biennial, or short-lived perennial forb.

Flower: Whiteflowers produced in small,umbrella-like clusters on2-cm-long stalksat the end of thestems.

Seeds/Fruit:Each flowerproduces 2joined seeds. Thenarrow seeds are6–7 mm long with apronounced beak (point).The seeds are green at first,then mature to shiny brown.

Leaves: The basal and stem leaves are

similar: fern-like, triangular in outline, and smooth tosoftly hairy. Each leaf is divided into smaller leafletsthat in turn are also divided. The bases of the leavesclasp the stem.

Stems: The branching stems grow 0.3–1.8 m tall(Cranston et al. 2000). The stems are hollow andfurrowed and bear a fringe of hairs at the stem nodes.

Roots: The thick, tuberous taproots are aggressive andspread rapidly, often extending nearly 2 m in the soil.Roots on mature plants are difficult to remove.


Similar Species

Exotics: Salad chervil (Anthriscus cerefolium) issimilar but is smaller and aromatic. Bur chervil(Anthriscus caucalis) has hairy leaves and seedscovered in short, hooked prickles.


Agricultural: Wild chervil competes with pasture andhay crops, which reduces carrying capacity and forageproduction. Livestock will graze it when it is immature,but it becomes unpalatable near maturity. It is generallynot problematic in cultivated crops, but it acts as a hostfor a viral disease that infects other plants in the samefamily, including carrots, parsnips, and celery. It isdifficult to control because of its very deep root systemand tolerance to herbicides (BC Ministry ofAgriculture, Food and Fisheries 1998).

Ecological: Wild chervil competes with other plantsfor light, water, space, and nutrients. It is able to shadeout smaller plants because of its tall stature. Since thisweed is well adapted to ditches, stream banks, andmoist woods, native riparian plant communities are atrisk. Wild chervil also grows along roadsides,fencelines, and rights-of-way.

Human: This plant is sometimes a component ofBritish wildflower seed mixes.

WILD CHERVILAnthriscus sylvestris (L.) Hoffm.Family: Apiaceaea (Parsley).



Legal Status: Regional Noxious: Fraser Valley.


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Impacts ____________________________________________


General requirements: Wild chervil grows under arange of conditions but thrives in wet to moistdisturbed sites, especially where soils are rich. In BC itgrows at low- to mid-elevations in fields, pastures, and

edges of woods, and along roadsides and fencelines.

Distribution: Wild chervil is spreading rapidly in theAbbotsford-Chilliwack areas of the Fraser Valley (BCMinistry of Agriculture, Food and Fisheries 1998) and

occurs in the province’s southeast (Douglas et al.1998). Recent infestations have been found in northernWashington.

Historical: Introduced from Europe, possibly inwildflower mixes.

Life cycle: This weed is considered a biennial but canpersist as a short-lived perennial by forming sprouts atthe side of the taproots. Usually it forms a rosette in thefirst year and produces seeds in the second year.

Mode of reproduction: By seed and from root buds atthe top of the root.

Seed production: This weed is a prolific seedproducer.


Dispersal: Birds, water, and human activity spreadseeds. Mowing after seed-set spreads seeds along roadsand rights-of-way.


BC Ministry of Agriculture, Food and Fisheries. 1998.Weed Alert—Wild Chervil.http://www.agf.gov.bc.ca/croplive/cropprot/chervil.htm

Cranston R., D. Ralph, and B. Wikeem. 2000. FieldGuide to Noxious and Other Selected Weeds of BritishColumbia. BC Ministry of Agriculture, Food andFisheries and Ministry of Forests.

Darbyshire, S. J., R. Hoeg, and J. Haverkort. 1999. Thebiology of Canadian weeds. 111. Anthriscus sylvestris.Canadian Journal of Plant Science 79: 671—682.


NS Department of Agriculture and Fisheries. 2001.Nova Scotia Noxious Weeds—Wild Chervil.http://www.gov.ns.ca/nsaf/rir/weeds/chervil.htm [June2001].

Biocontrol: None.

Mechanical: Rosettes and immature plants can becontrolled by hand-pulling or digging, but matureplants must be removed below the crown to prevent re-sprouting the following year (BC Ministry ofAgriculture, Food and Fisheries 1998). Frequentcultivation may prevent establishment. Mowing candeplete food reserves, but it must be done repeatedlybefore the plant sets seed.

Fire: The deep, extensive root system would not beaffected by fire.

Herbicides: Chemical control is often precluded duethe wet habitat wild chervil prefers. Mowing at pre-bloom and treating regrowth with mecoprop, dicamba,or clopyralid have been effective in Nova Scotia(Darbyshire et al. 1999). Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Learn to identify wild chervil

and take immediate action to control any infestations.Manage infested patches by grubbing out, applyingherbicides, or cutting to prevent seed-set. Cut and bagany flowering plants for burning or deep burial. Makesure equipment, vehicles, and footwear are clean beforeleaving infested sites, and do not move soil frominfested sites (BC Ministry of Agriculture, Food andFisheries 1998).


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Management ________________________________________

References __________________________________________

Integrated Management SummaryThe deep root system and its resistance toherbicides make this weed very difficult tomanage. New infestations must be removedimmediately before the root systems develop.For established stands, a combination ofherbicides with timed mowing or grazing hasbeen effective (NS Department of Agricultureand Fisheries 2001).


Growth form: Annual or winterannual forb.

Flower: Flowers are 13 mmin diameter, yellow, with 4 petals.Flowers are borne in small terminalclusters up to 30 cm long.

Seeds/Fruit: Seed pods are smooth,4–5 cm long and 2 mm wide, and havea constricted beak that often includesthe uppermost seed. Seeds are small,smooth, round, and black to purplishbrown (Stubbendieck et al. 1995).

Leaves: Leaves are alternate, 5–15 cmlong, and 2.5–10.0 cm wide. Lower leavesare deeply lobed, and upper leaves aremerely toothed and may be short stalked or stalkless.

Stems: Mature plants are 0.3–1.0 m tall. Stems areerect and branched near the top. The lower stems arecoarsely hairy.

Roots: Shallow taproot.

Seedling: Seed leaves(cotyledons) are kidney-shapedand smooth. True leaves arealternate and hairy and varyconsiderably in size and shape.The stem is also hairy, especiallynear its base (Carey et al. 1993).

Similar Species

Exotics: None.

Natives: White mustard (Brassicahirta) resembles wild mustard,except that the pods of white mustardare covered with coarse hairs. Thisspecies is rare in southern BC (Douglaset al. 1998).

Agricultural: Wild mustard can invade grain and otherfield crops as well as disturbed areas. It can reducecrop yields, lower the crop value, and reduce livestockforage production in rangeland.



WILD MUSTARD

Brassica kaber (DC.) L.C. WheelerFamily: Brassicaceae (Mustard).

Other Scientific Names: Sinapis arvensis.

Other Common Names: Charlock mustard, kaber mustard.



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Impacts ____________________________________________


General requirements: In BC, wild mustard is foundat lower elevations at the coast and Interior grasslands,where it grows under dry to average soil moistureconditions on fields and disturbed habitats. In otherareas it is commonly found in crops and alongroadsides and cultivated fields.

Distribution: Rare in southwestern and south-centralBC (Douglas et al. 1998) and considered a major

concern only in the Peace River agricultural reportingregion.


Life cycle: Wild mustard relies on insects forpollination (Kunin 1997).


Seed production: Each plant produces 2,000–3,500seeds.

Seed bank: Seeds may remain viable in the soil forseveral years.





Durgan, B. R., J. P. Yenish, R. J. Daml, and D. W.Miller. 1997. Broadleaf weed control in hard springwheat (Triticum aestivum) with F8426. WeedTechnology 11: 489–495.

Kunin, W. E. 1997. Population size and density effectsin pollination: Pollinator foraging and plantreproductive success in experimental arrays of Brassicakaber. Journal of Ecology 85: 225–234.

Stubbendieck, J., G. Y. Friisoe, and M. R. Bolick.1995. Wild mustard. Weeds of Nebraska and the GreatPlains. Lincoln: Nebraska Department of Agriculture,Bureau of Plant Industry.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996. Wildmustard. Weeds of the West. Western Society of WeedScience, in cooperation with the Western United StatesLand Grant Universities Cooperative ExtensionServices, Newark, CA.

Biocontrol: None.

Mechanical: Cut or pull plants before seed-set.


Herbicides: Metsulfuron-methyl, 2,4-D, or dicambahave been effective in the early spring before the plantsbolt. A combination of 2,4-D and dicamba is alsoeffective (Durgan et al. 1997). Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Cultivate fields in mid- to latespring. Apply a contact herbicide before planting.


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Management ________________________________________

References __________________________________________

Integrated Management SummaryCut, pull, or apply appropriate herbicides tonew infestations. Prevent establishment of newpopulations by maintaining vigorous perennialplant communities on rangeland and pasture.Seed disturbed areas to perennial plants tominimize opportunities for invasion.



Flower: Droopingspikelets in a loose,

open panicle. Each spikelet has apair of large glumes (paperyscales) with 2–3 florets inside.Flowering begins in July.

Seeds/Fruit: Seeds are variablein colour (Frankton and Mulligan1970), but all seeds have a dark,bent, twisted awn about 3 cmlong. Seeds are hairy at the basewith a circular scar at the point ofseed attachment.

Leaves: Leaf blades are flat, long(20–30 cm), and broad (1.0–1.5 cmwide). A papery membrane (ligule)is visible at the base of the blade.

Stems: Erect, hollow stems grow 0.6–1.5 m tall.

Roots: Extensive, fibrous root system.

Seedling: The seedling leaves are slightly hairyand are twisted counter-clockwise. The seedremains on the root of the seedling (Royerand Dickinson 1999).

Similar Species

Exotics: Cultivated oats (Avena sativa) resembles wildoats but wild oats are much larger plants. Cultivatedoat seeds have short, straight awns and lack the circularscar. The open panicle with its large, drooping spikeletsbearing long, bent awns distinguishes wild oats fromother grains and grasses.

Natives: None.

Agricultural: Responsible for losses in cropproductivity through competition (BC Ministry ofAgriculture and Food 1984). It also results in loweredgrain quality and increased costs for grain cleaning andweed control (tillage and herbicides). Long awns on theseed can injure livestock. Wild oats is an alternativehost for virus diseases of grains and alfalfa.

Ecological: Virtually absent on undisturbed lands butcan invade disturbed sites, where its rapid growth and

development make it competitive. The plant is adaptedto a wide range of environmental conditions, but itbecomes a serious weed in temperate climates withmoist soils. Chemicals from the roots inhibit seedgermination and seedling growth of other species(Sharma and Vanden Born 1978).

Human: Improved cultivated oat varieties have beendeveloped through genetic crossing with wild oats.

WILD OATS

Avena fatua L.Family: Poaceae (Grass).


Other Common Names: Oatgrass, poor oats, wheat oats.



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General requirements: In BC, wild oats occurs infields and disturbed areas. In the Prairies, it is found ingrain fields, oilseed crop fields, fallow fields,roadsides, waste places, disturbed areas, and gardens.

Distribution: Present in all agricultural reporting

regions but occurs rarely in the Peace River region(Sharma and Vanden Born 1978). It also occurs in allCanadian provinces.


Life cycle: Germinates mostly in the spring or autumn,

Impacts ____________________________________________

but it can germinate throughout the growing seasonduring cool, moist conditions (Alberta Agriculture1995). Roots and shoots develop quickly and plantsbegin flowering by early July, depending on growingconditions and geographic location. Flowering mayextend up to 6 weeks, with seed-set and seed sheddingoccurring over a prolonged time (Sharma and VandenBorn 1978).


Seed production: Seed production can range from 20to 250 seeds/plant.

Seed bank: Seeds are initially dormant but mostgerminate in the first and second spring. On croplandin Alberta, about 3% remained dormant and viable forup to 12 years (Alberta Agriculture 1995).

Dispersal: Most seeds are shed around the parentplants. Seeds are moved with the crop duringharvesting when the plant is mixed with crops.

Hybridization: Cultivated oats and wild oats hybridizereadily.

Biocontrol: None, but wild oats is susceptible to manyof the same organisms as cultivated oats, includinginsects, nematodes, fungi, and a virus.

Mechanical: Plants can be managed with cultivation atgermination but especially before seed-set. Tilling ismost effective at the 3-leaf growth stage to minimizeremoval of soil moisture and nutrients. Mowing canprevent seed-set in heavy to moderate infestations. Themowed wild oats can be used for green feed or silage ifthe seeds have started to set (Alberta Agriculture 1995).

Fire: Seeds are not tolerant to high temperatures.Burning windrow of straw immediately after harvestingcan reduce viable seeds (Sharma and Vanden Born1978).

Herbicides: Numerous herbicides are registered for wildoats control in various commodities. Overuse of someherbicides has resulted in a major increase in herbicide-resistant wild oats populations. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Autumn-seeded crops, such asfall rye and winter wheat, can reduce wild oatsinfestations on cropland, especially if a dense covercrop establishes (Sharma and Vanden Born 1978).Forage crops used in a crop rotation also are effective.


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Management ________________________________________

Integrated Management SummaryWild oats is a serious and persistent problem incultivated crops because the plants set seedbefore crops mature, and seeds can remainviable in the soil for long periods (BC Ministryof Agriculture and Food 1984). Selectiveherbicides or cultivation can kill the plantsbefore they set seed. Growing competitivecrops, which reduce the amount of wild oatsseed produced, or burning wild oats seeds afterharvest, can also prevent or reduce infestations.A competitive stand of perennial vegetationwill discourage this weed on rangelands andpastures.

Alberta Agriculture. 1995. Wild Oats.http://www.agric.gov.ab.ca/pests/weeds/64010310.html

BC Ministry of Agriculture and Food. 1984. WeedSeries Fact Sheet—Wild Oats. Agdex 640.


Royer, F., and R. Dickinson 1999. Weeds of Canadaand the Northern United States. Edmonton: Universityof Alberta Press.

Sharma, M. P., and W. H. Vanden Born. 1978. Thebiology of Canadian weeds. 27. Avena fatua L.Canadian Journal of Plant Science 58: 141–157.

References __________________________________________


Growth form:Annual grass.

Flower: Theinflorescence is a spreadingpanicle 15–30 cm wideand not fully extendedfrom the leaf sheath.

Seeds/Fruit: Seeds aresmooth, shiny, olive brown toblack.

Leaves: Leaf blades are 10–25 mmwide. Sheaths are open with long,spreading hairs. There is a fringeof dense hairs (ligule) at the baseof the leaf blade.

Stems: Mature plants are 0.6–1.8 m tall with erectstems that branch at the base.

Roots: Not rhizomatous, short fibrous root system.

Seedling: Both surfaces of the leaf blade as well as thesheath are densely hairy. The back of midrib often hasa row of hairs protruding at a 90° angle. Auriclesare lacking, and the ligule is hair-like. Thelarge, shiny, dark brown to black seedcoat often persists on the root system.

Similar Species

Exotics: Common witchgrass (Panicumcapillare) has erect panicles and shorterspikelets.

Natives: None.

Agricultural: One of the fastest-spreading weeds inthe US corn belt, this weed is a vigorous competitor inrow crops (Whitson et al. 1996) and appears to be mostcompetitive in corn, soybeans, and beans (Wilson1992).

Ecological: Not a problem in rangelands or naturalareas.



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Impacts ____________________________________________

WILD PROSO MILLET

Panicum miliaceum L.Family: Poaceae (Grass).


Other Common Names: Proso millet, broom corn millet,common millet.


General requirements: Commonly found in crops(especially corn) and along field edges and roadsides.In BC, it is particularly adapted to sandy, droughtysoils, but it can grow on a wide range of soils.

Distribution: The plant occurs infrequently in theprovince but has been found in cornfields in theKamloops, Salmon Arm, Enderby, and Abbotsfordareas. It is present in the Okanagan, Thompson,Mainland, and Peace River agricultural reportingregions. It is common in much of the US.

Historical: Introduced from Eurasia. Grown for humanconsumption, chicken feed, or bird seed.

Life cycle: Seeds germinate in spring and throughoutthe summer when soil temperatures rise (Wilson 1992).Flowering begins in July and continues throughout thesummer. Seeds mature from late August throughSeptember, depending on geographic location (Wilson1992).



Seed production: A single plant may produce400–2,100 seeds (Wilson 1992).

Seed bank: Seeds can remain viable in the soil for 5 or

more years.



Wilson, R. G. 1992. Wild proso millet. NebGuide G83-648-A. Cooperative Extension, University of NebraskaInstitute of Agriculture and Natural Resources.http://ianrwww.unl.edu/pubs/weeds/g648.htm [5 Mar99].

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Wild-proso millet. Weeds of the West. Western Societyof Weed Science, in cooperation with the WesternUnited States Land Grant Universities CooperativeExtension Services, Newark, CA.

Biocontrol: None.

Mechanical: Properly timed cultivation (Wilson 1992),beginning as soon as the crop emerges and continuinguntil it begins to close the row, can provide up to 95%management (Wilson 1992).


Herbicides: In non-crop situations glyphosate willprovide excellent management (Wilson 1992).Numerous herbicides are registered for pre-plant, pre-emergence, and post-emergence control in annual cropsin Canada. Consult the most recent edition of BCMinistry of Agriculture, Food and Fisheries CropProduction Guides for specific recommendations.Before applying herbicides, read the label for fulluse and precautionary instructions.

Cultural/Preventive: Always select clean, high-quality, certified seed. Clean farm equipment,especially combines, before leaving an infested field(Wilson 1992). Crop rotation can be used to managewild proso millet. Alfalfa has been used for long-termmanagement. Regular mowing prevents seedproduction (Wilson 1992).


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Management ________________________________________

References __________________________________________

Integrated Management SummaryCombining early season cultivation with eitherpre-planting or post-emergence herbicides hasresulted in the most consistent control (Wilson1992).

Growth form: Perennialor annual sedge.

Flower: Flowers areyellowish brown in appearance. Threeto 9 leaf-like bracts under the flowerclusters are longer than the flowers.

Seeds/Fruit: Seeds are yellowish,triangular, oblong, and 1–2 mm long.

Leaves: Grass-like leaves originatefrom the base of each stem, whilelong, leaf-like bracts radiate outfrom a common point just belowthe umbrella-like flower cluster.

Stems: Plants range from 10 to70 cm tall, with 3-ranked leavesand 3-angled pithy stems.

Roots: Long, scaly rhizomes havesmall tubers at the tips thatare dark, unevenly globe-shaped, and edible, tastingsomething like almonds.

Seedling: Stems are triangular in cross-section. Leavesare smooth, hairless, and deeply keeled. The plant isyellowish to pale green (Carey et al. 1993).

Other: The leaves have a sweet scent.

Similar Species

Exotics: Purple nutsedge (Cyperus rotundus) is verysimilar in appearance, but it has a purple seed head, itstubers are bitter, and its leaves taper to an abrupt pointrather than a gradual one as in yellow nutsedge.


Agricultural: The nutsedges are difficult weeds tomanage in cultivated fields, often forming a solid coverover large areas in sorghum and alfalfa pastures, floodplains, dams, and ditches, and along streams androadsides (Parker 1972). Yellow nutsedge can also betroublesome in crops like onions, potatoes, beans, andcorn (Whitson et al. 1996). It reduces yield and qualityby competing for light, water, and nutrients, and by

interfering with pesticide applications and harvestoperations (Ackley et al. 1996). It is increasing as aconcern to berry production in BC.

Ecological: Yellow nutsedge is a noxious weed of wetsoil. Infestations often start in wet areas and thenspread outward.


YELLOW NUTSEDGE

Cyperus esculentus L. var.leptostachyus Boeckl.Family: Cyperaceae (Sedge).


Other Common Names: Yellow nut-grass, chufa, chufa flatsedge,galingale.



188

Impacts ____________________________________________


Habitat and Ecology __________________________________General requirements: Yellow nutsedge is found inmany soil types but is common on well-drained, sandysoils or damp to wet sites. It can commonly be found inirrigated crops, along streams, around lakes and ponds,wet fields, and wet prairies.

Distribution: In BC, this plant is causing concern incoastal agricultural areas, where it grows on moist to

moderately dry sites. It is found only in the Mainlandagricultural reporting region, where it is considered amajor concern. It is also found in cultivated agriculturallands, turfgrass, nurseries, and native habitats ineastern Canada and throughout the US.

Historical: Introduced from Europe. The tubers areedible by humans and wildlife.

Biocontrol: None.

Mechanical: May be pulled or dug before seedproduction. It is important to pull the entire root systemto avoid regrowth from underground root buds.


Herbicides: Very difficult to gain long-term controlwith herbicides. Bentazon is registered for control inblueberries. Non-selective control is possible withrepeat glyphosate applications. Consult the most recentedition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Prevent the establishment of newinfestations by minimizing disturbance and dispersaland maintaining perennial plant communities.

Ackley, J. A., H. P. Wilson, and T. E. Hines. 1996.Yellow nutsedge (Cyperus esculentus) manage POSTwith acetolactate synthase-inhibiting herbicides. WeedTechnology 10: 576–580.


Douglas, G. W., D. Meidinger, and J. Pojar, eds. 2001.Illustrated Flora of British Columbia. Vol. 6.Monocotyledons (Acoraceae through Najadaceae).Province of British Columbia.

Holm, L. G., D. L. Plucknett, J. V. Pancho, J. P.Herberger. 1991. The World’s Worst Weeds. Malabar,FL: Krieger Publishing Co.

Parker, K. F. 1972. Yellow nutsedge—Cyperusesculentus L. An Illustrated Guide to Arizona Weeds.Tucson: University of Arizona Press.http://www.uapress.arizona.edu/online.bks/weeds/yellonut.htm [10 Sept 99].

US Department of Agriculture. Undated. MidwesternWetland Flora: Field Office Guide to Plant Species.USDA. Soil Conservation Service, Midwest NationalTechnical Center, Lincoln, NB. Jamestown, ND:Northern Prairie Wildlife Research Center Home Page.http://www.npwrc.usgs.gov/resource/othrdata/plntguid/plntguid.htm [16 Jul 97].

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Yellow nutsedge. Weeds of the West. Western Societyof Weed Science, in cooperation with the WesternUnited States Land Grant Universities CooperativeExtension Services, Newark, CA.


189

Life cycle: Plants are yellowish green. Flowers appearone per scale, with many scales per spikelet (USDA.Undated). Flowering occurs from July to October.

Mode of reproduction: By rhizomes, tubers, andsometimes seed. Rhizomes radiate from the main plant,ending in bulbs or tubers that may produce new plants.

Seed production: Under favourable conditions largeamounts of seed can be produced (Holm et al. 1991).




References __________________________________________

Integrated Management SummaryMechanical and/or chemical managementmethods can be used to eliminate seedproduction and deplete the nutrient root reserves.Land use practices that maintain perennial plantcover will help prevent the spread of yellownutsedge. Management efforts must be directedat prevention of tuber formation.

Management ________________________________________


Growth form:Winter annual forb.

Flower: Flower headsare yellow, located singly at theends of branches. Flower headsare distinguished by sharp,straw-colouredthorns, whichare up to 2 cmlong.

Seeds/Fruit:Yellowstarthistle has 2types of seeds:plumed andplumeless.

Leaves: Basal leaves are deeply lobed;upper leaves are entire and sharplypointed.

Stems: Mature plants are 60–90 cmtall and have rigid, branching, wingedstems covered with cottony hairs(Whitson et al. 1996).

Roots: Taproot.

Seedling: Seedlings haveoblong, tongue-shaped cotyledons(Herzog and Randall 1998).

Similar Species

Exotics: None in BC.


Agricultural: In horses yellow starthistle causes aneurological disorder called “chewing disease”(Maddox et al. 1985).

Ecological: A pioneering plant that becomesestablished on disturbed land. In the US, it forms dense

infestations, reducing the available forage for livestockand wildlife. It may have allelopathic effects on someassociated native species (Maddox et al. 1985).


YELLOW STARTHISTLE

Centaurea solstitialis L.Family: Asteraceae (Sunflower).


Other Common Names: St. Barnaby’s thistle.



190

General requirements: Yellow starthistle invadesrangelands, pastures, roadsides, cropland, and disturbedhabitats. It is intolerant of shade and requires light forrosette and taproot development (FEIS 1996). It canestablish on deep, well-drained soils as well as onshallow, rocky soils that receive 25–100 cm of annualprecipitation.

Distribution: Yellow starthistle is not known to occur inthe province but is well established in the US PacificNorthwest, where it appears to be spreading. It occupiesmid- to high-elevation sites and appears best adapted to

dry habitats formerly dominated by big sagebrush(Artemisia tridentata), bluebunch wheatgrass (Elymusspicatus), Idaho fescue (Festuca idahoensis), andSandberg bluegrass (Poa secunda) (Sheley et al. 1999).


Life cycle: Seedlings usually emerge in the autumn,form rosettes, and begin growing a taproot. Rootgrowth continues throughout the winter. Yellowstarthistle bolts in late spring and flowers from Junethrough August, depending on elevation and latitude.


Impacts ____________________________________________

FEIS—Fire Effects Information System. 1996.Prescribed Fire and Fire Effects Research Work Unit,Rocky Mountain Research Station (producer). USForest Service. http://www.fs.fed.us/database/feis/ [12Mar 98].

Hastings, M. S., and J. M. DiTomasso. 1996. Firecontrols yellow starthistle in California grasslands.Restoration and Management Notes 14: 124–128.

Herzog, P., and J. Randall. 1998. Element stewardshipabstract for Centaurea solstitialis, yellow starthistle.The Nature Conservancy, Wildland WeedsManagement and Research Program.http://tncweeds.ucdavis.edu/esadocs/documnts/centsol.html [30 Jul 98].

Maddox, D. M., A. Mayfield, and N. H. Poritz. 1985.Distribution of yellow starthistle (Centaureasolstitialis) and Russian knapweed (Centaurea repens).Weed Science 33: 315–327.

Rees, N. E., P. C. Quimby, Jr., G .L. Piper,E. M. Coombs, C. E. Turner, N. R. Spencer,and L. V. Knutson, eds. 1996. BiologicalControl of Weeds in the West. WesternSociety of Weed Science, in cooperationwith USDA Agricultural Research Service,Montana Department of Agriculture, andMontana State University.

Sheley, R. L., L. C. Larson, and J. S. Jacobs. 1999.Yellow starthistle. In R. L. Sheley and J. K. Petroff,eds. Biology and Management of Noxious RangelandWeeds. Corvallis: Oregon State University Press.

Whitson, T. D. (ed.), L. C. Burrill, S. A. Dewey, D. W.Cudney, B. E. Nelson, R. D. Lee, R. Parker. 1996.Yellow starthistle. Weeds of the West. Western Societyof Weed Science, in cooperation with the WesternUnited States Land Grant Universities CooperativeExtension Services, Newark, CA.

Management__________________________________________


191


Seed production: Plants usually produce 700–1,000seeds/plant, but vigorous plants may produce up to170,000 seeds/plant (Herzog and Randall 1998; FEIS1996).

Seed bank: Seeds may remain viable for several years(Herzog and Randall 1998).

Dispersal: Plumed and plumeless seeds are dispersedat different times. Plumed seeds are dispersed by windshortly after maturity. Plumeless seeds remain in theseed head until it disintegrates in the autumn or winter.


References __________________________________________

Biocontrol: None available in the province. The mostcommonly used biological control agent in the US isBangasternus orientalis, a seed head weevil. Larvaefeed on the seeds and can destroy up to 60% of theseeds in a head (Rees et al. 1996).

Mechanical: Hand-pulling can be used to removesmall infestations of yellow starthistle. Mowing can beused to control larger infestations. Mowing alone isineffective as a management method but can be helpfulin stressing yellow starthistle plants that grow abovedesirable seeded species during re-vegetation (Sheleyet al. 1999).

Fire: Hastings and DiTomasso (1996) reported thatyellow starthistle was controlled with prescribedburning in California grasslands. Burning should beconducted during the early flowering stage beforeseed-set.

Herbicides: Herbicides are most effective whenapplied from the seedling to bolt stages. Picloram,dicamba, and 2,4-D are the most commonly usedherbicides for this weed. Consult the most recent

edition of BC Ministry of Agriculture, Food andFisheries Crop Production Guides for specificrecommendations. Before applying herbicides, readthe label for full use and precautionary instructions.

Cultural/Preventive: Grazing management shouldaim to promote plant communities with perennialgrasses and forbs that provide good ground cover.

Integrated Management Summary Integrate herbicide applications with seeding ofcompetitive grasses where applicable. Cattleand sheep will graze yellow starthistle before ithas spines, but the plant may need to be grazedseveral times in a growing season forsuccessful management. As this weed is notcurrently in the province, all efforts must bedirected toward maintaining a competitiveperennial cover and to preventing plants foundfrom going to seed.



Flower: Flowers are brightyellow and resemble

snapdragons. Flowers are arrangedin a raceme at the ends of thebranches.

Seeds/Fruit: Seed capsules areround-ovate, 5–10 mm long, and2-celled. Seeds are brown orblack, circular, and surroundedby a notched wing.

Leaves: Leaves are soft, lance-shaped,and pale green. Leaves are mainlyalternate, but lower leaves appear tobe opposite due to crowding.

Stems: Mature plants are 10–80 cm tall with 1–25smooth, erect floral stems.

Roots: Taproots may be up to 1 m long. Lateral rootsmay be several meters long and can developadventitious buds that may form newplants.


Similar Species

Exotics: Leaves of Dalmatian toadflax (Linariadalmatica) are shorter, wider, and broad-based,clasping the stem.


Agricultural: Yellow toadflax contains a glucosidethat is mildly poisonous to cattle (Morishita 1991). Theplant is considered unpalatable to cattle and poisoningsare rare.

Ecological: Yellow toadflax establishes in open areasbut is adapted to a wide range of environmentalconditions (Saner et al. 1995). The plant spreads

rapidly from adventitious buds on creeping rootsystems. The plant competes with native grasses andforbs and can alter species diversity on some sites.Dense populations can also reduce forage productionfor livestock and wildlife.


YELLOW TOADFLAXLinaria vulgaris P. MillerFamily: Scrophulariaceae (Figwort).


Other Common Names: Butter and eggs, wild snapdragon,common toadflax.



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General requirements: Seems best adapted to siteswith well-drained sandy or gravelly soils, dry summers,and open, sparsely vegetated sites (Lajeunesse 1999).In BC it is found in grasslands and open forests and ondisturbed sites such as roadsides, railroad tracks,logged forests, cultivated fields, and gravel pits.

Distribution: Occurs in all Canadian provinces andterritories and throughout the continental US (Saner etal. 1995). In BC it is locally abundant in the Okanagan,Similkameen, Thompson, Boundary, East Kootenay,

and Cariboo regions (Powell et al. 1994). It is presentin all of the province’s agricultural reporting regionsexcept the Mainland and Vancouver Island but is notconsidered a major concern in any region.

Historical: Introduced from Eurasia as an ornamentalplant.

Life cycle: Prostrate stems emerge in autumn and aretolerant to freezing. These stems develop into floralstems the following year that begin growth about thesame time as new seedlings in mid-April, depending on

Impacts ____________________________________________

geographic location. Plants flower from May throughAugust, and seeds mature from July to October (Saneret al. 1995).


Seed production: A mature plant can produce up to30,000 seeds annually, and a single stem can containover 5,000 seeds (Saner et al. 1995).

Seed bank: Seeds can remain dormant for up to 10years.

Dispersal: Primarily by wind but may also bedispersed by water and ants (Rutledge and McLendon.Undated).


Lajeunesse, S. 1999. Dalmatian and yellow toadflax. InR. L. Sheley and J. K. Petroff, eds. Biology andManagement of Noxious Rangeland Weeds. Corvallis:Oregon State University Press.

McClay, A. S. 1992. Effects of Brachypteroluspulicarius (L.) (Coleoptera: Nitidulidae) on floweringand seed production of common toadflax. TheCanadian Entomologist 124: 631–636.

Morishita, D. W. 1991. Dalmatian toadflax, yellowtoadflax, black henbane, and tansymustard:Importance, distribution, and control. In L. F. James, J.O. Evans, M. H. Ralphs, and R. D. Child, eds. NoxiousRange Weeds. Boulder, CO: Westview Press.


Robocker, W. C. 1974. Life history, ecology, andcontrol of Dalmatian toadflax. Technical Bulletin No.79. Pullman: Washington Agricultural ExperimentStation.


Biocontrol: Five species occur in BC that could beused for yellow toadflax: Brachypterolus pulicarius(beetle), Calophasia lunula (moth), Eteobaleaintermediella (moth), Gymnaetron antirrhini (weevil),and Mecinus janthinus (beetle).

Mechanical: Cutting or mowing removes current-yeargrowth and can also reduce seed production anddispersal. However, they do not kill the plant and arenot recommended (Lajeunesse 1999).

Fire: Burning is not recommended because of theplant’s large, deep root system (Saner et al. 1995).

Herbicides: Difficult to manage with herbicides.Herbicides should be applied during flowering whencarbohydrate reserves in the root are at their lowest.Picloram, dicamba, and picloram with 2,4-D have allbeen effective in some situations (Sebastian and Beck1999). Consult the most recent edition of BC Ministryof Agriculture, Food and Fisheries Crop ProductionGuides for specific recommendations. Before applyingherbicides, read the label for full use andprecautionary instructions.

Cultural/Preventive: Hand-pulling can be effective,especially in coarse-textured soils where roots can be

pulled easily. Repeated applications may be requireduntil the seed bank and root fragments have beendepleted. Seed disturbed areas to perennial grasses andforbs to provide ground cover and competition.Manage for vigorous perennial plant communities.


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Management ________________________________________

References __________________________________________

Integrated Management SummaryIntegrated management must combineprevention, cultural control, mechanicalcontrol, herbicides, and biocontrol agents. Fornew and small infestations, hand-pulling andmechanical methods may be appropriate tolimit seed production and spread, but repeatedapplications of treatments are likely. For largerinfestations, herbicides may be appropriate.For very large infestations, the only practicalsolution may be biocontrol. Seeding disturbedareas to perennial grasses and forbs andadjusting management practices to maintainvigorous perennial plant communities allcontribute to managing this plant successfully.


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Saner, M. A., D. R. Clements, M. R. Hall, D. J.Doohan, and C. W. Crompton. 1995. The biology ofCanadian weeds. 105. Linaria vulgaris Mill. CanadianJournal of Plant Science 75: 525–537.

Sebastian, J. R., and K. G. Beck. 1999. The influenceof picloram or picloram plus 2,4-D applied for 1, 2, or3 years on cover, density and control of yellowtoadflax on Colorado rangeland. Research ProgressReport of the Western Society of Weed Science. pp.36–37.

Zimmerman, J. A. C. 1996. Ecology and distribution ofLinaria vulgaris (L.) Miller, Scrophulariaceae. USGSColorado Plateau Field Station, Southwest Exotic PlantMapping Project.http://www.usgs.nau.edu/swemp/Info_pages/plants/Linaria/linariatitle.html [14 Jan 98].


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a guide to weeds in british columbia · growth form: annual forb. flower: several small (less than...

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