WEED

IDENTIFICATION

- TERMINOLOGY

C. Shumway B. Scott

THIS IS A GLOSSARY OF TERMS USED IN THE IDENTIFICATION OF

WEED SPECIES. PROPER IDENTIFICATION IS A KEY COMPONENT ON

THE EFFICIENT USE OF WEED CONTROL MEASURES.

ON THE CONTACT INFORMATION AND RESOURCE PAGE THERE ARE A

NUMBER OF SITES THAT HAVE EXCELLENT IDENTIFICATION KEYS

BASED ON THESE CHARACTERISTICS.

CONTACT INFORMATION AND RESOURCES

THIS IS FOR GENERAL USE; REMEMBER TO USE ALL OTHER RESOURCES

AVAILABLE TO EVALUATE THE IDENTIFICATION OF A WEED SPECIES.

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WEED IDENTIFICATION GLOSSARY - A - Le

ASEXUAL REPRODUCTION –

BULB

RHIZOME

ROOT

STOLON

TUBER

COTYLEDON

GROWTH HABIT

DECUMBENT

ERECT

PROSTRATE

ROSETTE

GLABROUS

JOINTING & BOLTING

LEAF ARRANGEMENT–

ALTERNATE

OPPOSITE

ROSETTE

WHORLED

LEAF MORPHOLOGY – GENERAL

BLADE

COMPOUND

INTERNODE

NODE

SHAPE

SIMPLE

WEED IDENTIFICATION GLOSSARY - Le - Z

LEAF MORPHOLOGY – DICOT

LEAFLET

OCREA

PETIOLE

STIPULE

TENDRIL

THORN (SPINE)

LEAF MORPHOLOGY – MONOCOT

AURICLE

COLLAR

LIGULE

SHEATH

LEAF VENATION –

NET

PARALLEL

LIFE CYCLE

PUBESCENCE

ROOT

ADVENTITIOUS

BRACE

TAP

SEEDLING EMERGENCE

EPIGEAL

HYPOGEAL

STEM

STEM SHAPE

TILLER

ASEXUAL PROPAGATION - A major area for the growth and

identification of weed species is the natural production of

vegetative plant structures that have the capacity to produce new

plants. Asexual propagation is the best way to maintain some

species. Many of these vegetative structures are modified stems

and include structures produced below the soil line (bulbs,

rhizomes, roots, and tubers) and above the soil (stolons). Many of

these serve as food storage areas for the plant. True roots,

although less prevalent, are also found in several wee species.

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BULBS: consist of

very short stems with

closely packed leaves

arranged in concentric

circles around the

stem. The leaves are

swollen with stored

food e.g. wild onion

and wild garlic. A

terminal bud will

produce the flowering

shoot and the lateral

(axillary) buds will

produce new plants.

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RHIZOMES - are stems which grow horizontally under the ground. in some cases the

underground stems are swollen with food reserves. The terminal bud turns upwards to

produce the vegetative shoot. Examples below include Johnsongrass and sedge.

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One type of

asexual

propagation is a

‘true’ root system

producing

adventitious

shoots. It is

found in the

nightshade

(solanaceae) and

the asteraceae

family [typically

in the thistle

group]. New

plants emerge

from rootstocks

buried below the

soil surface.

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STOLON - is a horizontal stem that can produce new adventitious roots. A term

that is also used is a runner.

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TUBERS - Are thick, underground stems that develop at the end of rhizomes. The

tuber has all the parts of a normal stem, including nodes and internodes. Below

is the production of tubers from a rhizome on a sedge plant.

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COTYLEDON (SEED LEAVES):

Function of this structure is

primarily storage of reserves

for use during germination;

tissue will be photosynthetic

with the duration of this

function being variable based

on the species.

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COTYLEDON

SHAPES

GROWTH HABIT

– DECUMBENT :

The term used

to describe the

growth of the

stem when they

are prostrate

with leaves

growing

upwards.

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GROWTH HABIT - ERECT

The term used to describe the upright growth of the stem

and leaves.

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GROWTH HABIT –

PROSTRATE : The

term used to describe

the growth of the

stem when they are

flat on the ground.

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GROWTH HABIT – ROSETTE: The term used to describe the growth of the stem

when the internodes are not elongated (compressed).

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PUBESCENCE: Plants that

have trichomes on any plant

part (leaf, stem, petiole, etc.).

These trichomes can be

dense to sparse with the

location being very specific

within a weed species.

GLABROUS: Without any

trichomes.:

JOINTING – A term used to describe the

elongation of the internode in monocots; allows

for a separation of the nodes of the plant.

BOLTING - A term used to describe the

elongation of the internode in dicots

which typically have a rosette type of

growth; allows for a separation of the

nodes of the plant. Typical in biennials.

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NODE

INTERNODE

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LEAF ARRANGEMENT – ALTERNATE:

Has one leaf which emerges per node

on the stem.

LEAF ARRANGEMENT – OPPOSITE;

Has two leaves which emerge per

node on the stem. LEAF ARRANGEMENT – WHORLED: Has more

than two leaves emerging from the same node

on the stem. MENU

LEAF BLADE – A general term used to describe the part of the leaf that is

photosynthetic.

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COMPOUND LEAF – A leaf that has

multiple leaflets; the point of attachment

to the stem is still a petiole but the

leaflets are attached to a structure called

a rachis.

SIMPLE LEAF – Has a single blade

and is attached to the plant by a

petiole.

NODES – Are enlarged regions of

stems that are generally solid and

where leaves are attached; will also

have axillary buds for continued

vegetative and reproductive

growth.

INTERNODES - The region of a

stem between two successive

nodes.

STIPULE - Is an appendage of the

young leaf and is attached to the

base of the petiole.

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LEAF SHAPES

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LEAFLET – A term

used to describe

the individual

blades on a

compound leaf.

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OCREA - A unique structure that we find in in some dicots. They are described as fused

stipules that form a sheath around the stem. These are found within the circle with (a) curly

dock (Rumex spp.) and (b) smartweeds (Polygonum spp.).

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PETIOLE: The stalk that attaches a leaf blade to a stem of a simple leaf. Compound leave’s

point of attachment to the stem is still a petiole but the leaflets are attached to a structure

called a rachis (the main axis of a compound leaf).

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PETIOLE

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TENDRIL - Is a slender, coiling

modified leaf or stem which

aids in the support of the

shoot system.

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THORNS (SPINES) - Are

found on various plant

parts and are typically

hard structures with

sharp, stiff ends. The

terms are used

interchangeably, but

thorns are structures

typically derived from

shoots, whereas spines

typically develop from

leaves.

ILLUSTRATIONS OF THE VARIOUS COMPONENT ASSOCIATED WITH THE COLLAR

REGION IN A MONOCOT AND MAY INCLUDE THE LIGULE , AURICLE , AND THE

SHEATH

TYPES OF

SHEATHSMENU

AURICLES - are claw like

appendages found at the

junction of the leaf blade

and the leaf sheath.

LIGULE - is a structure on the

inside of the collar. A ligule is

either membranous, hairy or

absent.

LIGULE

AURICLE

SHEATH

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LIGULE

AURICLE

SHEATHS - Are

tubular extensions

of a grass leaf that

surrounds the

stem.

classifications are

based on the

general

appearance and

can be

overlapping, split,

or united.

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NETTED-VEINED

LEAVES – These

leaves have a few

prominent veins from

which a large number

of minor veins arise.

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PARALLEL-VEINED

LEAVES- These leaves

contain veins about

equal in size and running

parallel. Growth of grass

leaves takes place by

elongation near the base.

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LIFE CYCLE

ANNUALS- Plants that complete their entire life cycle (from seed to seed)

in a single growing season.

BIENNIALS- Require two growing seasons to complete their life cycle.

Vegetative growth occurs during the first season (vernalization occurs

during the winter), and flowering and fruiting occur in the second

season.

PERENNIALS- Have an indefinite life period based on species and

environment. They differ from other classifications in that they do not

cease growth after reproduction.

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ROOTS, ADVENTITIOUS:

Refers to roots arising

from areas not related to

the true root (product of

the radicle).

ROOT, TAP: The

descending axis of a

plant derived from the

radicle.

ROOT, BRACE – A type

of adventitious root that

grows from the stem

above-ground and serves

for support of the plant.

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STEM- The main body of a

plant, usually the ascending

axis, whether above or below

the ground in opposition to

the descending axis or root.

Stems, but not roots, produce

nodes and axillary buds.

STEM SHAPE - Varies in plant types. The classifications include: round, triangular

(typical of sedges, oval, and square (typical of the mint family.

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TILLER (OR TO DESCIBE THE PROCESS IS

TILLERING) - is the production of additional

stems from the activity of the axillary buds.

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ILLUSTRATION OF VARIOUS COTYLEDON SHAPES>

RETURN

Linear oblong lanceolate spatulate oval

round ovate kidney butterfly

EMERGENCE TYPES

In hypogeal germination, the epicotyl or plumule

will grow and emerge above the soil surface.

However, the cotyledons and the first node will

remain below the soil surface. Typical of

monocots and cool-season dicots.

In epigeal emergence, we have the epicotyl,

cotyledon, and the first node moving above the

soil surface. Typical of most dicots.

coleoptile

plumule

hypocotyl

cotyledon

First node

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This is a link to the MP44 published by the UA/CES. This contains information

on labeled herbicides in the state of Arkansas. This publication also contains

information of resistance management, spray information and REIs.

This is a link to the International Survey of Herbicide Resistant Weeds. This

website contains current information on herbicide resistance weeds and their

management.

For further information or comments, please contact the following personnel:

Cal Shumway, Agronomist Bob Scott, Weed Scientist

COAT, Arkansas State University Lonoke Agricultural Center

State University, AR 72467 Lonoke AR 72086

Email: cshumway@astate.edu Email: bscott@uaex.edu

ISHRW

MP44

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AgWeb Online Field Guide - WeedsUniversity of Arkansas-

Weed ID

These are links to several websites that have information on weed species

identification.

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