technical notes - home | nrcs · • vegetative windbreaks add to a beautiful countryside. probably...
TRANSCRIPT
TECHNICAL NOTES U.S. DEPARTMENT OF AGRICULTURE NATURAL RESOURCES CONSERVATION SERVICE PLANT MATERIALS - 13 SPOKANE, WASHINGTON
FEBRUARY, 2005
WINDBREAK, SHELTERBELT, and LANDSCAPING TECHNOLOGY
This Technical Note #13 is subdivided into the following Sections: Section 13.1 – “Trees Against the Wind”, a Pacific Northwest Extension
Publication. http://www.wsu.edu/pmc_nrcs/Docs/PNW005.pdf.
USDA NRCS OCTOBER 2005
rees against
the indWW
TT
PNW0005
A Pacific Northwest Extension Publication
Washington State University • University of Idaho •Oregon State University
Cover photo: A newly established windbreaklocated in southern Idaho that utilizes fabric mulchand drip irrigation.
Designed by
Gerald Steffen, MFA,CAHE Information
Trees against the Wind
PNW005
Material in this publication is for agriculturists in Idaho, Oregon,and Washington to use in planning, establishing, and caring forwindbreaks, shelterbelts, and living snow fences. Though much ofthe information will apply in other areas, the authors suggest askingadvice from a forester or conservationist before following speciesand spacing recommendations.
The authors graciously acknowledge the contributions made to thisbulletin by professionals working in the public domain.
Extensively revised by
Donald P. Hanley, PhD, CF,WSU Extension Forester
Gary Kuhn, MS,USDA-NRCS Agroforester
Trees against the Wind
ontentsCWhat is a Windbreak? ....................................... 1Windbreak Benefits ........................................... 1
Improved Crop Yields ................................. 2Orchards .................................................... 3Wind Erosion Reduction .............................. 4Better Livestock Performance ...................... 4Odor Mitigation by Windbreaks .................. 5Wildlife Enhancement—Especially Birds ...... 7Sound Barriers ............................................ 8More Beautiful Countryside ........................ 8
Structural Wind Barriers .................................... 8Why Are Not More Windbreaks Successful? ...... 9How Many Years Are Needed to Grow
a Windbreak?.............................................. 9What Does a Successful Windbreak Require? .. 10Planning Your Windbreak ............................... 11
Climate ..................................................... 11Soil ........................................................... 11Protection ................................................. 12Farmstead and Feedlot Windbreaks........... 12Field Windbreaks ...................................... 12Center-Pivot Irrigation Designs ................. 13Sound Barriers .......................................... 14Living Snow Fence .................................... 14
How Many Rows to Plant? .............................. 15“Traditional Windbreak Design” ..................... 15
Shrubs ...................................................... 15Deciduous Trees ....................................... 15Evergreens ................................................ 15Tree and Shrub Spacing Is Important ........ 17
Twin-Row, High Density WindbreakDesign—A New Alternative ....................... 18
Windbreak Density ......................................... 19Selecting Species to Plant ............................... 19
Planting .................................................... 19Special Windbreak Designs ............................. 22
Dryland Plantings ..................................... 22High Elevations and “Frost Pockets”.......... 22
Windbreaks for Wildlife ................................... 22A Place to Nest ......................................... 22Food and Foraging Sites ........................... 22Shelter from Predation—Escape Cover ...... 24Shelter from Weather ................................ 24
Windbreak Species and MatureCharacteristics .......................................... 24Nursery Stock ........................................... 24Nonrooted Cuttings ................................. 25Site Preparation ........................................ 26Care of Trees before Planting .................... 26Planting the Tree ...................................... 26Hand Planting Techniques ........................ 27
Weed Barrier Fabric Mulch for Treeand Shrub Plantings.................................. 27Application of Weed Barrier by Machine ... 29
Post Planting Care .......................................... 30Irrigation .................................................. 30Weed Control ........................................... 30Cultivation ................................................ 31Herbicide Usage ....................................... 31Fertilizers .................................................. 31Iron Chlorosis ........................................... 32Timing Fertilizer Applications .................... 32Fertilizer Quantities ................................... 32
Protection ...................................................... 32Renovation of Old Plantings ........................... 33A Final Word................................................... 34Sources of Additional Information................... 35Sources of Planting Stock ............................... 35
State or Federal Nurseries ......................... 35Commercial Nurseries ............................... 35Soil Conservation Districts ........................ 35
Individual Species Characteristics: Shrubs ....... 36Individual Species Characteristics:
Deciduous Trees ....................................... 36Individual Species Characteristics: Evergreens .... 38Suggested Reading......................................... 40
TT
hat Is a Windbreak?A windbreak is a planting, usually of both treesand shrubs, designed and established to reduceundesirable effects of strong winds.
When the pioneers settled the treeless areas ofthe Northwest, they needed trees to provideshade and to give protection from the wind.Most farm and ranch plantings used fast-grow-ing trees such as Lombardy poplar, eastern cot-tonwood, and black locust. Windbreak designwas simple. The common practice was to plantone to six rows of a single species on a ratherclose spacing. The success of a planting dependedon the owner’s judgment regarding species, spac-ing, location, and the amount and kind of careneeded (Figure 1).
Northwest farmers and ranchers are still plant-ing windbreaks. The difference is they now canfollow recommendations giving them high
assurance of satisfactory windbreak performance.Much information has been gained throughresearch on how design, location, and propertree species affect windbreak efficiency. Thisbulletin is a guide for your use in planning,planting, and caring for a windbreak. Its recom-mendations are based on extensive windbreakresearch and experience in several states.
indbreak BenefitsYour need for a windbreak can be measured interms of the benefits you would derive (Figure 2).The major benefits of windbreaks are
• Improved farmstead environment. Homesprotected from cold winds use less energyfor heating (Figure 3).
• Improved crop yields.
• Reduced soil erosion.
he forest acts powerfully in checking the force of the winds
because the elastic swaying of the twigs and branches is
a very effective hindrance to the movement of air.
~Gifford Pinchot, 1905
0’ 100’
Velocity hereis about
10 M.P.H.
Toe of snowdrift will beabout here under severe
conditions
200’
Velocity hereis about
15 M.P.H.
35’
When open wind, velocity is 35 M.P.H.Wind currents are broken and lifted.
Figure 1. A dense windbreak that is properly designed and correctly located will reduce winds and controlsnow drifting. Note that a “traditional design” windbreak is illustrated here.
W
W
1
• Better livestock performance. Animals gainmore weight when protected.
• Vegetative windbreaks attract game andsongbirds.
• Windbreaks provide a buffer against loudnoises.
• Windbreaks help mitigate strong odors fromfeedlots and other localized sources.
• Vegetative windbreaks add to a beautifulcountryside.
Probably the single most important benefit of afarmstead windbreak is the reduction of energyrequired to heat a home. Energy savings are
further increased by the proper placement offoundation plantings around the home.
Recent studies show that windbreaks can reducewinter fuel consumption by 10% to 30%. Forexample, one study in Nebraska compared thefuel requirements of identical houses, in whicha constant inside temperature of 70°F was main-tained. The house protected by a windbreak used23% less fuel. Energy usage was compared fortwo identical, electrically heated homes in SouthDakota. A farmstead windbreak sheltered onehome; nothing sheltered the other. Inside tem-peratures were maintained at 70°F. The shelteredhome used 34% less electricity (Figure 4).
In addition to reducing the force of the wind,windbreaks also can reduce the wind-chilleffect on people outside the house. Studies ofthree-row windbreaks, where trees were 25 feettall, showed reduced wind velocities and wind-chill index (Figure 5).
Improved Crop YieldsA survey in South Dakota examined how wind-breaks influence crop yields. On 677 fields ofcorn, oats, and barley, yield increased 8 to 9bushels per acre due to windbreak protection.Alfalfa averaged 3/4 ton per acre more on 123 pro-tected fields. Corn silage from 13 protected fieldsshowed more than a 3-ton-per-acre increased
Figure 2. Windbreak benefits are numerous.
Windbreaks protect crops, soil, livestock,and humans while also improving air andwater quality, enhancing fish and wildlifehabitat, broadening biodiversity, and beau-tifying the landscape.
Conservation buffers allow farmers, ranchers,and homeowners to express their commit-ment to conservation.
Summary of Benefits
Figure 3. Windbreaks provide many benefits around homes and other outbuildings.
Environmental Purposesof Windbreaks
Structure protection
Screening
Noise abatement
Dust reduction
Beauty
Wildlife habitat
2
yield, and four fields of potatoes gained nearly48 cwt per acre due to protection by windbreaks.A Nebraska experiment showed 34 acres protectedby windbreaks produced the same amount ofcanning tomatoes and beans as 40 acres of simi-lar land without windbreak protection. A studyin southern Idaho reported yields of several fieldcrops increased by 1% to 7% in fields that hadwindbreak protection. In other areas, wherecereal grains are the prime crop, windbreakinfluences on crop yields are less conclusive(Figure 6).
In a South Dakota survey, nearly all farmers saidtheir field windbreaks more than pay for theground they occupy. Many commented favor-ably about the effects their windbreaks had onsoil blowing, crop damage, and drifting snow.
OrchardsOrchards need shelter against high winds, espe-cially during pollination and preharvest whenthe fruit is ripening. Fruit often is blown off thetrees or bruised and scarred in unprotectedorchards. Behind a good windbreak, you canspray, dust, and prune fruit trees with greatercontrol. The WSU Wenatchee Tree Fruit Researchand Extension Center reported bees are morenumerous in orchards having windbreak pro-tection. Honeybees and other pollinating insectsare more effective when sheltered against winds.Windbreaks reduce irrigation evaporation, andtrapped snow adds more soil moisture in thespring. An orchard owner in Idaho observed that
Evergreentrees
Dead air space
Deciduous shrubs
Evergreen shrub
Typical Foundation PlantingNo scale
Evergreenshrubs
Deciduoustree
North
Figure 4. Foundation planting around a home tosupplement a windbreak gives further energy savings.
Figure 5. A three-row windbreak significantly reduceswind velocity on the leeward side of the break.
-36
-24
-12
0
12
24
36
Win
d-c
hill
fac
tor
at 1
0°F
25 30
Effect of a three-row 25’ tallwindbreak on wind-chill factor
0 5 10 15 20
Wind velocity (unprotected) M.P.H.
Protected (75’ on leeward side)
Unprotected
Figure 6. Field windbreak benefits.
Weightedaverage cropyield increase
Corn—12%Barley—25%Hay—20%Soybeans—13%Winter Wheat—23%Spring Wheat—8%Yi
eld
in p
erce
nt
of
fiel
d n
orm
al
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20H00
20
40
60
80
100
120
140
160
Distance from windbreak in units of windbreak height(H=40 feet in this diagram)
Normal yield of unprotected field
3
his fruit crop from an orchard with windbreakprotection was consistently better than cropsfrom neighboring orchards without protection(Figure 7).
Wind Erosion ReductionSoil erosion caused by high winds is called winderosion. Land managers or owners can controlwind erosion in several ways: through the useof good plant cover; tillage practices that leavethe soil ridged or cloddy; or windbreaks thatreduce the wind velocity. Areas where erosionhazards are high call for a combination of mea-sures (Figure 8).
The wind can easily move fine soil particles, bothorganic and mineral. Often the soil particlesblowing from a field contain 10 to 20 times asmuch humus and plant nutrients as the heavierparticles that stay on the field.
Soil particles do not ordinarily blow until windvelocity reaches about 13 miles per hour at aheight of 1 foot above the ground. This is knownas “threshold velocity.” Above the thresholdvelocity, the capacity of winds to carry soil isproportional to the square of the wind speed.Therefore, small reductions in wind speed causegreat reductions in the rate of soil loss.
Conditions conducive to wind erosion on crop-land include:
• Loose, dry, and finely granulated soil
• Smooth soil surface with sparse or novegetative cover,
• Large crop areas, and
• Sufficient wind velocity to move soil.
Better Livestock PerformanceFeedlot and livestock windbreaks primarily pro-tect livestock from wind and windborne soil andsnow. Windbreak protection can significantlyreduce stress on animals and their feed require-ments. This protection results in better animal
Figure 7. Field windbreaks protecting orchards.
health, lower death loss, and lower feed costs(Figure 9).
In cold weather, cattle must increase food intakefor energy to keep body temperatures within aspecific comfort range. For example, a study inIndiana found energy requirements for cows ingood condition increased 13% for each 10-degree drop in wind-chill temperature below30°F. Cows in poor condition needed 30% moreenergy for each 10-degree drop.
Canadian researchers have reported cattle onwinter range require a 50% increase in feedenergy for normal activities and an additional20% to overcome the direct effects of exposureto cold temperatures and wind. They concludedadequate wind protection could reduce thedirect effects of cold by more than half. TheCanadian studies also indicated feeder cattle,
Figure 8. Windbreaks proved excellent protectionas far out as six to eight times tree height and fairprotection up to 10 times tree height.
Excellent protection to6–8 times tree height
Fair protection to10 times tree height
Protection diminishes at15–20 times tree height
4
when provided with wind shelter and kept dry,are not affected significantly by cold weather.
Iowa studies with calves and yearlings concludedfeed requirements were 7% greater in open lotsthan in lots with shelter.
Many livestock owners also have attested thatshade provided by windbreaks and other treeplantings helps animals during very hot sum-mer days. While this windbreak value has neverbeen quantified in pounds of livestock gain,the shade value of trees is, nonetheless, widelyrecognized.
Odor Mitigation by Windbreaks1
New university research in the Midwest andGreat Plains regions is experimenting with useof windbreaks as odor control mechanisms. Thisexciting windbreak application warrants contin-ued study and experimentation here in thePacific Northwest. While the majority of thisresearch focuses on hog production in Iowa andNebraska, the application appears useful to miti-gate odor at dairy, beef, and poultry enterprises.
Animal waste is becoming a major problem inthe U.S., where more than 1.4 billion tons ofmanure are produced annually. Most of themanure is concentrated, as production facilitiesand feedlots have become larger. Odor fromthese facilities is causing significant social prob-lems, especially as non-farm-based residentsencroach on traditionally agricultural land(Figure 10).
Windbreaks have the potential to be an effec-tive and inexpensive odor control device. Theodors produced from animal waste originatenear the ground and often stay close to theground due to temperature inversions, especiallyin the winter months. Windbreaks can act asinterceptors of this ground-based odor plume(Figure 11). According to the university research-ers, windbreaks can ameliorate livestock odorsin four primary ways:
Figure 9. Locate windbreaks that protect livestockso the snow deposition falls outside the feeding area.
Figure 10. Hypothetical windbreak system designfor a typical swine production facility. CourtesyIowa State University.
Figure 11. Schematic representation of turbulenceand zone of potential odor dilution. Courtesy IowaState University.
A. Prevailing wind direction
Fence Access lane FenceFeed bunk
Drainage
Drainage ditch formelting snow or rainfall
150’–200’
75’–100’
B. Prevailing wind direction
Fence Access lane FenceFeed bunk
Drainage
Drainage ditch formelting snow or rainfall
150’–200’
75’–100’
Service roads
Wastestorage
Storagelagoon
Field for landapplication
(Maintain 100–200 feet distance for snow deposition)
Ventilation
N
ShelterbeltQuiet zone
0 4 8 12 16
h
Zone of plume dilution
1 This section is adapted from: Air Quality and Shelterbelts: Odor Mitigation and Livestock Production, A Literature Review. USDA NationalAgroforestry Center Sponsored Research Project. John Tyndall and Joe Colletti, Forestry Department, Iowa State University.
5
• Diluting gas odor concentrations into thelower atmosphere
• Encouraging dust and other aerosol deposi-tion by reducing wind speeds
• Physically intercepting dust and other aerosols
• Acting as a sink for the chemical constituentsof odor
Odor is composed of gaseous volatile com-pounds and particulate matter. Particulate mat-ter is a component of odor plumes and closelyrelated to odor from cattle, swine, and poultry(housing) facilities and from outdoor lots forswine, cattle, and sheep. Animal dust and otherparticulates easily absorb and carry the major-ity of the odorous compounds. Dust can carrymany times more molecules of some odorouscompounds than the same volume of air, thusconcentrating odors.
Windbreaks, especially those composed of ever-green tree species, serve as physical interceptorsof dust and other aerosols. As air moves acrossvegetative surfaces, needles and leaves captureand remove some of the dust, gas, and micro-bial burden normally carried by the wind. Thisremoval occurs mostly by way of a dry windborneroute, in raindrops, or in rain splash droplets.The total surface area of leafy plants is very large,
often exceeding the surface area of the soil con-taining those plants by as much as 20-fold. Theamount of leaf surface area positively favors theinterception of dust and other aerosols.
Little is known about the ability of trees andother plants to ameliorate odor by intake orabsorption of odorous chemicals or about themanagerial use of vegetation for this purpose.Compelling indirect evidence suggests this ispossible. In the last few decades, tremendousinterest has grown in the ability of plants toremove pollutants from the air. Several reviewsaddress the capability of plants to act as a sinkfor air contaminants.
Windbreaks also can mitigate odor from landapplications of liquid and solid manure (Figure12). Multiple windbreaks, used on both sides ofthe field and oriented perpendicular to prevail-ing winds, can offer diverse effects when applica-tion is primarily from liquid sources. A wind-break on the windward side of the field can cap-ture off-field particulates that would otherwisepass over the field surface and pick up volatileorganic compounds being emitted. This designencourages particulate deposition. A windbreakon the far side should create air turbulence andenhance odor dilution as well as intercept andencourage deposition of some particulates.Shelterbelt density should be increased above
Figure 12. Possible windbreak benefits in mitigating odor from field application of manure. CourtesyIowa State University.
Prevailing winds
Windward side shelterbelt
• Lower density (higherporosity) to allow throughflow and interception
• Off-field particulateelimination and overallparticulate control
Field border shelterbelt
• Higher density (lowerporosity) for increasedturbulence and dilution
• Particulate depositionon the windward andleeward sides
Crop field receiving manure
6
60% for maximum turbulence. To maximizeturbulence, wind speed must be at its prevailingrate. When using a two-belt system, make surethe field is wide enough to allow wind speed toregain prevailing velocity as it approaches theturbulence-creating windbreak. Since windbreakheight is also an important variable for odordilution, use taller tree species. Where fieldapplications of solid manure are involved, wind-break designs may need to maximize particu-late interception and deposition. To maximizethis particulate interception, allow some windto pass through the windbreak to encourageplant-particulate interactions. The use of lowerdensity belts (~50% density) should facilitatethis interaction.
Wildlife Enhancement—Especially BirdsFrom observations, wildlife biologists concludewindbreaks make very desirable nesting, brood-ing, and loafing areas for many game and song-birds. Some windbreak species provide significant
Figure 13. Windbreaks designed primarily forwildlife can have more plant diversity for anatural look.
Conifer
Largedeciduoustree
Tall shrubs
Shortshrubs
Grasses &legumes
Table 1. Windbreak Species Use by Wildlife for either Food or Cover†
Green Russian Siberian Blue Chokecherry Honeysuckle Caragana Buffalo- Americanash olive elm spruce berry plum
Pheasant X X X X X X
Gray partridge X X
Sharp-tailed grouse X X X X X X
California quail X X X X
Ruffed grouse X X X X X X
Wild turkey X X X X X X X
Mule deer X X X X X
White-tailed deer X X X X X X X
Mourning dove X X X X
Cottontail rabbit X X X X X X X
Squirrels X X X
Migratory songbirds X X X X X X X X X
†Slight modification of table by Erling Podell, USDA-NRCS, Bismark ND.
7
amounts of food for birds and other wildlife(Figure 13). Dense windbreaks also protect birdsfrom predators. During critical winter periods,windbreaks mean survival for large numbers ofbirds that would otherwise perish from the cold(Table 1).
Sound BarriersWindbreaks act as favorable deterrents to loud,low frequency sounds. Plant leaves, branches,and twigs all absorb sounds of different frequen-cies. The vibration of the tree parts absorbs thesounds. Heavier branches and trunks deflectsounds. Evergreens are preferred because of theiryear-round protection.
More Beautiful CountrysideWell-kept windbreaks and other tree plantingsundeniably enhance the aesthetic value of indi-vidual farms and the countryside. Aestheticallyimproving a farmstead by adding a good wind-break increases its economic value (Figure 14).When the buyer of a farm was told $1,000 wasadded to the sale price because of the windbreak,he replied, “I wouldn’t want the place withoutthe trees.”
tructural Wind BarriersIt may not be possible to establish a living wind-break in every instance where wind protectionis needed. A fence of boards, steel slats, or baledstraw will provide some windbreak benefits(Figure 15). The main advantages of structuralbarriers are requiring little space and providingprotection immediately upon construction.However, trees are the only barriers tall enoughto protect a large area. Protection from a struc-tural barrier is provided on the leeward side in azone 3 to 10 times the barrier’s height. Thus, an8-foot barrier would give its best protection in azone lying between 24 feet and 80 feet on itsleeward side. Such a barrier normally will reduceopen wind velocities by 40% to 60%.
A structural barrier should not present a solidface against the wind, since a solid face causessevere wind turbulence, resulting in a reversalof wind direction near the ground. Constructstructural barriers of slats or narrow boards withabout 50% density in the upper two-thirds ofits height and 25% density in the lower third.These density values also provide more uniformsnow deposition behind the barrier.
Structural barriers are not very effective in mini-mizing dust, and they have practically no wild-life value.
S
Figure 14. Windbreaks and other vegetation nearhomesteads add protection, value, and a distinctatmosphere to rural living.
Figure 15. Where soils are too shallow, structuredbarriers are used to trap snow.
8
hy Are Not More Wind-breaks Successful?You might logically ask: If windbreaks yield allthese benefits, why are not more windbreakssuccessfully established (Figure 16)? In the past,only about half the plantings made ever survivedin a manner to give good performance. Inad-equate care caused most failures. Weeds, lack ofwater, poor planting practices, uncontrolled live-stock, careless handling of farm equipmentwhen planting, and spraying weeds in nearbycrops are the main causes of windbreak failure.Other failures arise from poor planning, unfore-seen circumstances, or an attitude that trees willtake care of themselves once they are planted.Trees seldom perform satisfactorily without care.
Today, the use of the new fabric mulch hasgreatly enhanced the success of windbreakplantings in terms of both initial survival andtree and shrub growth (Figure 17). Living snowfences planted in southeastern Idaho showexcellent survival and growth. These Idaho liv-ing snow fences utilize drip irrigation systems.A few dryland field plantings in eastern Wash-ington, where natural precipitation is as lowas 10 inches, also show excellent growth andvigor.
ow Many Years AreNeeded to Grow a Windbreak?Many people think trees grow slowly. Somefarmers say slow growth is their major objec-tion to planting trees. In truth, irrigated wind-breaks grown at elevations below 5,000 feetprovide noticeable protection within 3 to 4 yearsand usually give effective protection within 7or 8 years. Dryland windbreaks ordinarily willgive effective protection in 7 to 12 years, depend-
W
Figure 16. Windbreaks are not common in manyinland northwest locations.
H
Figure 17. New wind-break with fabric mulchand drip irrigation hasan excellent chance toprovide protection in 3to 5 years.
9
ing on the soil and amount of precipitation. Pro-viding supplemental moisture for dryland wind-breaks not only improves tree survival but alsoincreases growth rates and shortens the estab-lishment period. Fabric mulches, established atthe time of planting, reduce these values signifi-cantly—possibly by a third.
Generally in the arid areas of the region, ever-greens have less height growth than deciduoustrees and shrubs during the first 10 years. Afterthat, the difference between growth rates becomesminimal. The average time needed for a wind-break to provide effective protection is shortwhen compared with the life span of the wind-break. Well cared for trees and shrubs oftenexceed 60 years before restoration is needed.
hat Does a SuccessfulWindbreak Require?Success in growing trees depends mostly on fac-tors you can control. Windbreaks can be grownsuccessfully in almost all areas of the PacificNorthwest where the climate and soil are suitablefor producing agricultural crops. Great advancesin tree and shrub stock and the techniques usedto establish them have made success a certainty.
For windbreaks to survive and make satisfactorygrowth where climate and soil are suitable,young trees need:
• A sound design, using the correct plantingstock.
• Careful handling of trees and shrubs priorto planting and post planting care.
• Adequate moisture, by rainfall or with highefficiency drip irrigation.
• Protection from weeds for at least 3 to 5 yearsafter planting.
• Protection from livestock and other grazinganimals.
• Periodic inspection for insect, rodent, anddisease damage.
Since your windbreak will be a long-term invest-ment, planning it well in advance of the plant-ing date is good business. Only a well-plannedwindbreak that receives good care can providemaximum protection and satisfaction (Figure18). Carefully consider the following:
• Locate the windbreak where it will be mosteffective.
• Design the planting to fit the available space.
• Allow ample room for good tree and shrubgrowth.
• Select tree and shrub species adapted to thegrowing conditions in your locality and thatwill best provide the benefits you want.
Figure 18. Windbreaks provide many environmental benefits.
Environmental Benefitsof Windbreaks
W
Wind erosion protection
Plant protection
Snow management
Irrigation efficiency
Livestock protection
Water quality
10
• Order needed trees and shrubs from a reliablenursery well ahead of planting time.
• Prepare the planting site at the correct timeso it is ready to receive the planting stock.
• Provide fencing, if necessary, to protect thenew planting from livestock, rodents, andrabbits.
• Arrange in advance for planting help andequipment so you will be ready to plant atthe correct time.
• Ensure refrigerated storage of your trees incase the weather does not permit you toplant.
• Design your irrigation system. Set the plant-ing date after water is available or plan a wayto give your young trees some supplementalwater if your planting is dry.
All these points deserve consideration. The restof this section gives details on planning anddesign as they pertain to different types of wind-breaks: farmstead or feedlot, field, sound barriers,and snow fences.
lanning Your Windbreak
ClimateMost settled areas below 5,000 feet elevation inthe Pacific Northwest have a favorable climatefor growing trees as long as appropriate irriga-tion supplements natural precipitation. As eleva-tion increases above 5,000 feet, the shortenedgrowing season and increased severity of wintermake establishment of trees more difficult.Choices of adaptable species become more lim-ited, and the trees make less annual growth thanthey do at lower elevations. Severe damagesometimes results as deep snow pack settles onyoung trees. Frozen ground also leads to winterdesiccation.
SoilSome tree species are naturally adapted to acidsoils, while others can easily endure a saline soilcondition. Some species grow naturally in boggyor swampy situations; others do best on dry sites.A deep, well-drained loam having neutral pHand average fertility is almost ideal for growinga variety of trees. Many sites are far from idealand present problems severe enough to preventsuccessful establishment of trees. These sites caninclude permanently wet areas, sites experienc-ing a high water table during the growing season,salty or alkaline soil, droughty and infertile soilsuch as deep sands and gravels, shallow soil overhardpan or bedrock, and extremely heavy claysoil.
Sometimes you can remedy a problem soil situ-ation by use of corrective practices such as drain-age, addition of organic matter, fertilization, orchiseling. A less expensive alternative is toselect a tree and shrub species mix that will growin your soil type.
Climate and soil characteristics vary greatlyamong different areas in the Pacific Northwest.These variations create many problems for treeplanting. They cause the optimum time forplanting to vary widely from area to area andinfluence the amount of care needed by treeplantings. Climate and soil variations make thechoice of species difficult for some areas.
P
Planning a windbreak is by far the most impor-tant step. This phase determines the location,size (number of rows), tree spacing, and treespecies to be used. A windbreak placed in thewrong place or configuration can create greaterproblems than those it was intended to solve.Also, during the planning phase, consider themethod and timing to plant and to maintainthe windbreak. Plan for irrigating and weedingto assure these jobs will be done at the righttimes.
The best time to plant a windbreak was
20 years ago—the next best time to begin
is today!
~Anonymous
11
ProtectionFencing the windbreak planting is usually nec-essary to protect it from damage by livestock andother grazing or browsing animals. Other pro-tective measures using pesticides may have tobe taken against rodents, rabbits, and insects.Disease and fire suppression and prevention isusually accomplished by pruning and weedcontrol. The best defense against these damagingagents is usually the selection of the best, mostadapted species. When planning the windbreak,be sure the needed measure for protection canbe taken. Otherwise, all efforts to establish asuccessful planting may be lost. Contact Coop-erative Extension or Natural Resources Conserva-tion Service personnel for fencing specificationsor other protective measures.
Farmstead and FeedlotWindbreaksLocate your windbreak as nearly as possible at aright angle to the prevailing winds. The wind-break at a right angle to the wind is more effectivethan one at an oblique angle to wind currents.Place the windbreak about 100 feet from thehouse or feedlot. This distance to the tallest treespecies row will provide good protection; yet, itavoids the sultry air conditions that normallyoccur near the leeward side of a dense windbreakon hot days. Maximum wind reduction occursfrom 2 to 5 times the height of the tallest row(Figure 19). This reduction is often representedby the formula: 2–5H, where H is the heightof the tallest tree or shrub row. If you have con-siderable snow in your locality, locate the wind-ward row of the windbreak about 150 feet frombuildings, driveways, or areas that need to stayfree of drifts. Should the arrangement of yourfarmstead make this impractical, consider asnow trap planting. A snow trap is a single ordouble row of dense shrubs paralleling the mainwindbreak 60 to 100 feet away on the windwardside. This snow trap arrangement will cause mostof the snowdrifts to accumulate between theshrubs and the main windbreak and not in thefarmstead. To provide the best protection, thewindbreak should have a density greater than
60%. This density level can be achieved usingthree to five rows of different tree and shrubspecies.
Extend your windbreak at each end 50 to 100feet beyond the boundaries of the house or feed-lot. This will prevent winds from whippingaround the windbreak into the area needingprotection. If you have to cross roads, driveways,or large ditches with your windbreak, try to makethe crossings at oblique angles to prevent directwind tunnels through the planting. Windbreaksneed not be straight but should be designed tofit the contour of the land to minimize watererosion problems. Curved windbreaks also areeasier to cultivate with equipment than thosehaving right-angle corners.
Field WindbreaksField windbreaks or shelterbelts are designed toprotect orchards, field crops, and bare soil fromthe effects of strong winds. Since field wind-breaks are permanent farm improvements, planthem carefully. Consider field boundaries, irri-gation systems, power lines, and roads becausethey are important in determining the locationof your windbreaks.
A. Prevailing wind directionProfile of typicalsnow drift aftersevere storms
Primary objector area in needof protection
Primary windbreakusually 3–8 rows
Sufficient space must be providedto store snow. Distance varies fromone region to another but usuallyranges from 100–200 feet.
B. Prevailing wind direction
Basic windbreak plantingAuxiliary wildlife planting
Wildlife food plot
zone free of drifted snow aftersevere storms with emergency
food and cover
Snow trap
50’
Snow trapplanting
Profile of snow driftafter severe storms
Figure 19. Locate windbreaks so the snow accumu-lation zone does not impact driveways and otherstructures.
12
In this region, fields subject to severe wind ero-sion may require multiple-row plantings alongthe field border, supplemented by parallel single-row plantings at intervals of 500 feet or less. Theusual velocity of erosive winds in your localityand the nature of your soil will determine thebest intervals to use between the supplementalplantings. If the usual maximum wind velocityin your locality exceeds 30 miles per hour andyou have light soils, place the supplementalwindbreaks 350 feet apart. Under less severeconditions, tall trees in single-row plantingsspaced 600 to 1,320 feet apart will give adequateprotection. The root competition zone is mini-mal when compared with the production gainsacross the field (Figure 20).
Center-Pivot Irrigation DesignsCenter-pivot irrigation systems have broughtgreat changes to the field windbreaks of thisregion. Many field windbreaks planted on sec-tion and half-mile lines have been modified oreliminated to fit this new irrigation technology.Straight-line windbreaks are just not compatiblewith the arc of the pivot systems. Existing wind-breaks are valuable resources; preserve themwhenever possible (Figure 21).
Where the windbreak must be modified, removethe trees completely rather than “top” them.“Topping” of most hardwoods is a short-livedalternative more expensive than removal in thelong run because of the numerous sprouts pro-duced. Establishment of low-growing (under 9feet) shrubs such as mugho pine, honeysuckle,or cotoneaster will provide some protection inthese gaps. The pivot can irrigate existing wind-breaks in the corners if you use “corner-catchers.”
The 16 corners of a four-field pivot system occupyabout 20% of the total area or 130 acres. Usethese corners to establish new field windbreaksthat give partial protection to the crop area. Planttrees established in these areas parallel to thecircumference of the crop area to make cultiva-
tion easier. Use normal between-row and between-tree spacing. The corners are also ideally suitedfor establishing woodlots for fence posts or fire-wood. Firewood values of windbreak species aregiven under Individual Species Characteristicsat the end of this bulletin. If these corners wereplanted for firewood, the estimated yield forirrigated black locust would be 10 cords per acreafter 10 years.2
Figure 21. Multi-row windbreak providing protectionand wildlife habitat at the corner of a pivot irrigatedfield.
Figure 20. The root competition zone is minimaland is negligible when compared with the gainsassociated across the field.
2 Estimate based on initial planting of 680 trees per acre (8x8 feet), which are thinned as necessary. After 10 years, approximately 480 treesper acre remain, having an average diameter of 4.5 inches (Miller, F. G. 1928. Black locust and how to grow it. University of Idaho Schoolof Forestry Bull. No. 2).
13
Sound BarriersWindbreaks and other tree plantings reducenoise from high-speed traffic or other surface-located sound sources. To make a windbreakan efficient sound barrier, follow these recom-mendations:
• Locate the planting as close to the noisesource as possible.
• If traffic on a highway is the source, theplanting should parallel the road.
• Plant tall, dense species for the main bodyof the planting.
• Use a dense shrub in the row next to thenoise source.
• Include at least one evergreen row for year-round abatement.
• Use as many rows as the available space willallow, using the recommended spacing.
• Make the planting twice as long as thedistance from the noise source to thereceiver.
Living Snow FenceSingle-row plantings of trees and shrubs paral-leling your driveways and roads will catch snowon the fields. An experiment in Kansas showeda well-designed windbreak caught 3.5 times asmuch snow as the best arrangement of struc-tural snow fences the researchers were able tomake. A snow fence planting should never becloser to the road than 100 feet (Figure 22).
In areas of eastern Washington, Oregon, andIdaho, deep snowdrifts accumulate on steepleeward slopes. They cause serious soil erosionwhen they melt, and they may delay springfarming operations. Living snow fences willcollect these drifts on gentler slopes on thewindward sides of the ridge crests. Hilltop snowfences should parallel the ridgelines. Place themabout 100 feet back from the ridge crests on thewindward sides of the ridge crests (Figure 23).
10–12H
Solid fence: H=6 feet; Density=100%35H-10H
35H-10HWyoming snow fence: H=12 feet; Density=50%
Vertical slot snow fence: H=3 feet; Density=50%35H-10H
Single-row deciduous shrub: H=6 feet; Density=50%
25H
25H 35H-10H
Single-row deciduous tree: H=20 feet; Density=25% to 35%35H-10H
Three-row conifer: H=20 feet; Density=60% to 80%35H-10H
Three-row conifer with a single shrub row as a trip rowConifer row: H=20 feet; Density=60% to 80%Shrub row: H=6 feet; Density=50%
35H-10H
Figure 22. When designing a living snow fence, theheight and density determine the storage capacity.
Figure 23. Living snow fences should be locatedback from driveways and roads. Place hilltop fences100 feet on the windward side of ridge crests.
14
Snow fence plantings may be planned as part ofyour field windbreak system. This kind of plant-ing has been used effectively to control driftingsoil on cropland. It prevents snow collection inirrigation ditches, along fence lines, and in road-ways. The choice of species for snow fenceplantings can greatly enhance their values forwildlife. Snow fences and field windbreaks serveas travel lanes for upland game birds (Figure 24).
ow Many Rows to Plant?
“Traditional WindbreakDesign”
ShrubsA windbreak must be dense near the ground.For this purpose, always choose a dense, bushydeciduous or evergreen shrub for the windwardrow of a multiple-row planting. Shrubs makeideal single-row or double-row low windbreaksaround yards and gardens. Shrubs often are cho-sen for living snow fences and supplementalplantings in field windbreak patterns. Landmanagers often recommend using shrub rowsfor protection while establishing evergreens ina windbreak (Figure 25).
Deciduous TreesDeciduous trees generally grow faster than ever-greens, thus providing earlier protection. Theyare commonly used for the middle rows in wind-break designs. Managers generally prefer decidu-ous trees and shrubs where severe soil freezing iscommon, as evergreens in these localized envi-ronments are prone to winter desiccation. Avoidusing Russian olive, as it will volunteer from seedif planted along ditch banks, in low pastures,or in wet wastelands. Siberian elm is generallynot recommended because it grows so rapidlythat the wood is brash, making it subject tobreakage from high winds. It also bears heavyseed crops, and the seedlings sometime create anuisance.
Figure 25. Skunkbush sumac is a desired shrubspecies in both irrigated and non-irrigatedwindbreaks.
Figure 24. Double twin-row living snow fenceinstalled along I-84 in southern Idaho.
H
EvergreensMany call evergreen trees the foundation for wind-breaks because they give year-round protection.Include them in all windbreaks wherever pos-sible. The traditional practice in establishingwindbreaks is to plant evergreens in one or twoleeward rows. In areas of deep soils and moder-ate climates, evergreens may be used for theentire windbreak, or when fabric mulch is used(Figure 26).
15
Plan your windbreak to fit the space you haveavailable, keeping in mind protection normallyincreases with the number of rows planted ifthe trees have room to grow.
A five-row planting makes a very desirable farm-stead windbreak (Figure 27). The best perfor-mance usually is obtained by using a differentkind of tree or shrub in each row. As an example,an irrigated planting of Siberian pea shrub, greenash, hybrid poplar, ponderosa pine, and bluespruce develops fast, has good height, offers highyear-long density, provides excellent bird habi-tat, and presents a pleasing appearance the yeararound. In a dryland planting, you could choosehoney locust instead of hybrid poplar and Aus-trian pine or Rocky Mountain juniper in placeof blue spruce. A windbreak of mixed speciesalso gives some protection against insects ordiseases damaging the entire planting (Table 2).
If limited space prevents planting a five-row wind-break, then use fewer rows rather than crowd thetrees. Results will be better with three rows thathave room to develop than with five seriouslyovercrowded rows. Crowding trees in a wind-break causes a loss of vigor due to severe com-petition as the trees try to increase in size. Treegrowth slows down at an early age and may
Table 2. Recommended Minimum Spacing between Trees and Shrubs.
Multiple-row Single-row Multiple-row Single-rowwindbreaks windbreaks windbreaks windbreaks
(feet) (feet) (feet) (feet)
Dense shrub 4 3 4 3
Medium-sizedeciduous 10 6 10 8
Tall deciduous 12 8 12 10
Medium evergreen 10 6 10 8
Tall evergreen 12 8 12 10
Irrigated or dryland receiving 16 inchesor more annual precipitation
Dryland plantings receiving 16 inchesor less annual precipitation
Note: The minimum spacing between rows for irrigated or dryland plantings receiving 16 inches or more annual precipitation is16 feet. The minimum spacing between rows for dryland plantings receiving less than 16 inches annual precipitation is 20 feet.
Figure 27. The Traditional Design utilizes five rowsof trees and shrubs.
Figure 26. Twin-row Rocky Mountain juniper usedas a living snow fence.
Prevailing wind
16
reach a point of almost no growth. The plant-ing becomes more susceptible to injury and lossfrom insects, disease, drought, and cold. Lowerlimbs die out early from too much shade in anovercrowded planting, thus making the wind-break much less effective because of lower den-sity next to the ground.
In dry areas, supplemental irrigation can reducethe number of rows used in a windbreak or makethe standard number of rows more effective. Forexample, two or three rows of trees given supple-mental irrigation easily equal five rows depend-ing only on natural precipitation. A well-devel-oped single row can be more satisfactory thanthree rows with inadequate irrigation. Use theguide in Table 3 if you must plant fewer thanfive rows in your windbreak.
Tree and Shrub Spacing IsImportantAdequate growing space tends to keep your treesthrifty. It gives assurance that your windbreakwill have a better appearance and a longer, use-
ful life. The recommended spacing will certainlylook quite large when planting seedling-size trees(Figure 28). Keep in mind that trees will growrapidly and fill the available space in just a fewyears. Use spacing between rows and betweentrees within rows that will:
• Leave adequate room for use of your tillageequipment.
• Provide your trees with ample room for goodgrowth.
• Avoid wind-whipping damage to trees inadjacent rows.
• Prevent early dieback of the lower limbs.
Spacing for windbreak trees varies by the typeof trees and shrubs used (Tables 2 and 4). Toowide spacing results in a significant time lagbefore wind reductions occur. Too narrow spac-ing provides early protection but can cause over-crowding, which later limits effectiveness dueto self-pruning. The spacing recommended inTable 2 will give your trees room to develop goodcrowns before strong competition sets in. These
Table 3. Traditional Design Planting Guide for Windbreaks.
Four rows Dense shrub Dense shrub Dense shrub Dense shrubMedium evergreen Medium deciduous Medium deciduous Medium deciduous
Tall evergreen Tall evergreen Tall deciduous Tall deciduousMedium evergreen Medium evergreen Medium evergreen Medium deciduous
Three rows Dense shrub Dense shrub Dense shrub Dense shrubTall evergreen Tall deciduous Medium deciduous Medium deciduous
Medium evergreen Medium evergreen Tall deciduous Medium evergreen
Two rows* Medium evergreen Dense shrub Dense shrub Dense shrubTall evergreen Tall evergreen Tall deciduous Medium deciduous
One row Tall evergreen Medium evergreen Tall deciduous Medium deciduous
Notes: Highest protection is recommended for farmstead and livestock protection areas.
*It is best to use the new twin-row design if you have only space for one or two rows.
If you have roomfor a windbreak
with only
These are combinations you may use. Each combination starts with the windward sideof the planting. Assuming equal success in establishment, the order of combinationsfrom left to right is from highest to lowest in year-round protection afforded by theplanting.
Highest protection Lowest protection
17
spacings are also within the optimum range forhighest windbreak efficiency. Wider spacing canbe used; however, more time is needed beforefull protection from the planting occurs.
When you have decided on the spacing you willuse, figure the number of trees you will need forthe planting. Order a few more trees than youactually need so you will have replacements. Mosttrees that die fail during the first growing season.
them 6 feet apart; if using tall evergreen trees,plant them 8 feet apart (Figure 29).
Twin-rows should be 25 to 50 feet apart. Use thesame tree or shrub species within a twin-row.
Some advantages of the new design are
• The 100-foot open area between windbreakand home can be reduced.
• The distance between twin-rows (25 to 50feet) is wide enough to be cultivated. A veg-etable garden, strawberry patch, or other spe-cialty crops are usually suitable in this area.
• The twin-rows provide rapid wind protectionand reduce the duration for weed controlbetween the two closely spaced rows.
• Drip irrigation can easily be installed betweenthe two closely spaced twin-rows.
• Windbreak renovation using twin-rows pro-vides continuous protection in a small area(Figure 30).
Figure 28. Clean cultivation improves survival andgrowth in all windbreaks.
win-Row, High DensityWindbreak Design—A NewAlternative
The USDA-Natural Resources Conservation Ser-vice has proposed a new twin-row, high-densitywindbreak design. This design is used exten-sively in the Great Plains region and is well suitedfor windbreak applications in the Pacific North-west. Trees or shrubs are planted every 4 to 8feet within the row with two rows planted 6 to8 feet apart. If using shrubs, plant them 4 to 5feet apart; if using medium evergreen trees, plant
This design is excellent for living snow fences,
supplemental or renovation plantings, and
for windbreak applications where space is
limited.
T
Figure 29. In the twin-row design, trees and shrubsare planted 4-8 feet apart within the row with tworows planted 6-8 feet apart. Use the same tree orshrub species within the row.
1 2 3
6’ 6’ 6’25’–50’ 25’–50’
18
indbreak DensityA key component in the design of any wind-break is the ultimate density attained. Densityor wind porosity is the percentage of structuralelements used to stop the wind. As densityincreases, protection immediately adjacent tothe break generally increases at the expense ofless protection farther from the barrier. Densityis also an important factor in snow movement,such as with a living snow fence. It is generallybest to follow the tree planting recommenda-tions in this bulletin to ensure the density willbe at least 40% to 60% for field windbreaksand 60% to 80% for farmstead and livestockprotection. Living snow fences provide the bestprotection when the density is in the 60% to80% range (Figure 31).
electing Species to Plant
PlantingPlant trees and shrubs in a well-prepared, firm,moist, and weed-free seedbed. Keep trees moistand cool from the time they arrive from thenursery until they are planted. In the actualplanting, set the roots into the ground in asnatural a position as possible. Do not bend orplant them in a “j” fashion. Plant at the same
W
S
Figure 30. Clean cultivated Eastern redcedar is usedin this windbreak renovation. Rocky Mountain juniperis the preferred species in the Pacific Northwest.
Figure 31. Windbreak density influences the leewardwind protection zone.
H distancefrom windbreak
Miles per hour
% of openwind speed
depth the trees grew in the nursery. Firmly packmoist soil around the roots. If you have ques-tions about the planting process, the Extensionbulletin “Plant Your Trees Right” (PNW Bull. No.33) is available from any county extensionoffice in the Pacific Northwest.
The selection of tree and shrub species must sat-isfy three basic requirements: 1) they must grow,
H distancefrom windbreak
Miles per hour
% of openwind speed
H distancefrom windbreak
Miles per hour
% of openwind speed
H distancefrom windbreak
Miles per hour
% of openwind speed
Open wind speed 20 M.P.H.Deciduous 25%–35% density
5H 10H 15H 20H 30H
10 13 16 17 20
50% 65% 80% 85% 100%
Open wind speed 20 M.P.H.Conifer 40%–60% density
5H 10H 15H 20H 30H
6 10 12 15 19
30% 50% 60% 75% 95%
Open wind speed 20 M.P.H.Multi-row 60%–80% density
5H 10H 15H 20H 30H
5 7 13 17 19
25% 35% 65% 85% 95%
Open wind speed 20 M.P.H.Solid fence 100% density
5H 10H 15H 20H 30H
5 14 18 19 20
25% 70% 90% 95% 100%
19
2) they must block the wind and, 3) they mustbe aesthetically pleasing to the owner. For thesereasons and because of the variations in localenvironments of Idaho, Washington, and Oregon,we include only a brief list of recommended
Traditional Windbreak Design—Suggested Species—in Priority Order
Dense shrub Medium-size Tall deciduous Tall evergreen Medium-sizedeciduous evergreen
species in this publication. Read the speciesdescriptions and ask advice on your choice ofspecies before making final selections. Local soiland water tables may limit the usefulness of aspecies (Table 4).
New Twin-Row Windbreak Design—Suggested Species—in Priority Order
Dense Medium-size Tallshrub evergreen evergreen
20
• Siberian peashrub (Caragana)
• Skunkbushsumac
• Common lilac
• Honeysuckle1
• Wild rose
• Red osierdogwood
• Nanking cherry
• Serviceberry2
Notes:1 Suggested varieties Amur, or Freedom.2 Not recommended on soils with pH greater than 7.5 because of iron deficiency.3 Suggested varieties flowering, manchurian, siberian.4 Use on leeward side only.5 Suggested varieties siouxland, robusta, ID hybrid, carolina.6 Avoid use in riparian areas and along irrigation ditches.7 Supplementary irrigation generally required for best growth.8 Willamette Valley and Interior Valley regions of SW Oregon only.
• Choke cherry
• American plum
• Crabapple3
• Hackberry
• Artic bluewillow2,4
• Sandbar willow
• Silver buffalo-berry
• Bur oak
• Green ash
• Honey locust4
• Golden willow2
• Hybrid poplar2,5
• Russian olive6
• Colorado bluespruce
• Austrian pine
• Norway spruce
• Ponderosa pine
• Scotch pine
• Douglas-fir7
• Incense cedar8
• RockyMountainjuniper
• Northernwhitecedar
• Easternredcedar
• Austrian pine
• Blue spruce
• Scotch pine
• Ponderosa pine
• Rocky Mountainjuniper
• Austrian pine
• Northern whitecedar
• Eastern redcedar
• Siberian pea shrub(Caragana)
• Skunkbush sumac
• Common lilac
• Honeysuckle
Tabl
e 4.
Win
dbre
ak S
peci
es a
nd M
atur
e C
hara
cter
istic
s U
nder
Arid
Con
ditio
ns.
Spec
ies
Mat
ure
Effe
ctiv
eC
row
nM
inim
umSa
line
soil
Win
ter
dam
age
hei
gh
tlif
e sp
anw
idth
pre
cip
itat
ion
tole
ran
cere
sist
ance
(fee
t)(f
eet)
(inch
es)
Shru
bs
Sibe
rian
pea
shr
ub10
8010
10ex
celle
ntex
celle
nt
(Car
agan
a)Sk
unkb
ush
sum
ac10
20 +
810
exce
llent
exce
llent
Com
mon
lila
c10
20 +
1015
good
exce
llent
Am
ur h
oney
suck
le8
207
12fa
irex
celle
ntC
omm
on p
rivet
1020
815
good
good
Nan
king
che
rry
615
415
fair
fair
Peki
ng c
oton
east
er5
204
12fa
irfa
irM
ugho
pin
e8
508
20fa
irfa
ir
Dec
iduo
us t
rees
Russ
ian
oliv
e30
3020
12ex
celle
ntex
celle
ntG
olde
n w
illow
3560
3015
good
exce
llent
Blac
k w
illow
4060
3520
exce
llent
exce
llent
Blac
k lo
cust
5050
4015
fair
fair
Hon
ey lo
cust
4060
2012
good
fair
Hyb
rid p
opla
r50
3030
15go
odex
celle
ntG
reen
ash
6050
4015
good
good
Lom
bard
y p
opla
r70
3015
20go
odfa
ir
Ever
gre
ens
Rock
y M
ount
ain
juni
per
2060
1512
exce
llent
exce
llent
Nor
ther
n w
hite
ced
ar35
5020
20p
oor
fair
Ince
nse
ceda
r60
5020
12fa
irfa
irA
ustr
ian
pin
e40
6030
20fa
irgo
odSc
otch
pin
e40
4020
15fa
irgo
odBl
ue s
pru
ce40
8025
20go
odex
celle
ntN
orw
ay s
pru
ce60
6025
15fa
irgo
odPo
nder
osa
pin
e60
8030
12fa
irgo
odD
ougl
as-f
ir160
6025
18go
odgo
odLo
dgep
ole
pin
e240
6020
12go
odex
celle
nt
Mat
ure
heig
ht =
exp
ecte
d m
atur
e tr
ee h
eigh
t in
feet
whe
n gr
own
unde
r m
ediu
m o
r fa
ir gr
owin
g co
nditi
ons.
Cro
wn
wid
th =
exp
ecte
d m
atur
e cr
own
wid
th in
feet
whe
n gr
own
unde
r m
ediu
m o
r fa
ir gr
owin
g co
nditi
ons.
Min
imum
pre
cip
itatio
n =
the
leas
t am
ount
of a
nnua
l pre
cip
itatio
n in
inch
es e
xpec
ted
to r
esul
t in
sat
isfa
ctor
y su
rviv
al a
nd g
row
th.
1 D
ougl
as-f
ir an
d lo
dgep
ole
pin
e ar
e re
com
men
ded
for
wet
ter
site
s, if
irrig
atio
n is
not
ava
ilabl
e.2
Lodg
epol
e p
ine
is o
ften
use
d ne
ar t
he c
oast
whe
re t
he s
oil i
s ve
r y s
andy
. In
this
situ
atio
n it
is c
omm
only
cal
led
shor
e p
ine.
21
pecial Windbreak Designs
Dryland PlantingsIf you have less than 20 inches of annual pre-cipitation and you cannot provide supplementalirrigation, the best shrub species to use areSiberian pea shrub, (Caragana), and skunkbushsumac. Excellent tree species include RockyMountain juniper, black locust, and Austrianpine. Do not plant black willow, golden willow,hybrid poplar, or Lombardy poplar in low rain-fall areas without supplementary irrigation.
High Elevations and “Frost-Pockets”All species listed at the end of this bulletin dowell up to 5,000 feet, with the exception of blacklocust in localities subject to hard frosts in earlyfall. Local topographic features can create widelydifferent growing conditions in areas having thesame elevation. The most reliable species forhigh elevation plantings are Siberian pea shrub,common lilac, golden willow, hybrid poplar,ponderosa pine, blue spruce, and Rocky Moun-tain juniper.
Low depressions or “frost-pockets” where thetopography traps cold air can cause minimumtemperatures as much as 10°F below those ofadjacent lands. These sites can have growing sea-sons substantially shorter than those on adja-cent lands of the same elevation. We recommendhigh elevation species in these localized areas.
indbreaks for Wildlife3
A Place to NestShelterbelts provide nesting habitat for a widevariety of birds and other wildlife species. At least57 kinds of birds are known to use windbreaksin the United States during the breeding season.Mourning doves nest and call in windbreak trees
but forage nearby for the seeds they eat. Birdssuch as the black-billed cuckoo (“rain bird”), housewren, gray catbird, and northern oriole conductnearly all their activities within the windbreak.American robins, kingbirds, brown thrashers,and American goldfinches sing and nest in wind-breaks but forage both in and out of them. Otherspecies, including squirrels and cottontail rab-bits, nest in windbreaks, and white-tailed deerwith fawns use windbreaks for cover (Table 5).
Food and Foraging SitesWindbreaks provide food for wildlife. Whenwildlife forages in adjacent areas, windbreaksprovide protective cover. Foods potentially avail-able in windbreaks include fruits, nuts, acorns,seeds, foliage, and insects or other invertebrates.Availability of these foods varies seasonally anddepends largely on what is planted or growingin the windbreak. Trees and shrubs producefruits, and some hold them into winter, a timewhen food is often critical for survival but gen-erally less available. Wild turkeys, pheasants,quail, squirrels, deer, and songbirds use acorns,nuts, and other seeds from trees such as elm,maple, and ash. Seeds also may be available fromgrasses or herbaceous plants growing in thewindbreak or from wildlife food plots plantedwithin or adjacent to the woody vegetation.Foliage such as leaves or other plant parts mayprovide food for browsing animals such as deer.Insects and other invertebrates are importantfoods for many birds, particularly during nest-ing periods, and for various small field mice andshrews. Windbreaks provide foraging sites thatwould otherwise be unavailable. Chickadeesglean along branches, peeking in and undercrevices in the bark for insects to eat. Windbreakspecies such as hackberry, hawthorn, blackcherry, autumn olive, honeysuckle, and othersserve as nectar sources and habitat for butter-flies, honeybees, and hummingbirds.
Food availability near shelterbelts is also impor-tant for many species. In fact, pheasants gener-
W
S
3 Adapted from Designing Tree Plantings for Wildlife—Prairie Farm Rehabilitation Administration, Shelterbelt Centre, Indian Head, Saskatchewan,Canada.
22
Table 5. Examples of windbreak plants that benefit wildlife and their primary wildlife values.
Table indicates which seasons of the year activity occurs: mostly during summer and fall (S), fall andwinter (W), or include browse (B). Bold letter indicates primary emphasis. (From USDA-NRCS sources).
Songbirds Gamebirds Fur & gamemammals
Plants1,2 Overall wildlife Nesting Food Cover Food Cover Food Covervalue
Conifers (Excellent winter cover, food, and nesting sites)
Rocky Mtn. juniper Excellent + W SW W SW B SWNorthern whitecedar Good–Excel + SW SW B SWSpruce Good ++ SW SW SWPine Good–Excel + S SW S SW B SWDouglas-fir Fair + SW SW SWLodgepole pine Fair + SW SW SW
Deciduous trees (Nesting and foraging sites, food, canopy and habitat structure)
Cottonwood/poplar Fair + S S B SFlowering crabapples Excellent ++ W S W S WB SHawthorn Good ++ W S W S B SHoneylocust Fair + S SServiceberry Good + S S S S B S
Tall shrubs (Nesting sites, food, cover near ground)
Skunkbush sumac Excellent + W SW W SW B SWAmur maple Excellent + S S S S B SCommon privet Good + S SW S S SHoneysuckles Excellent ++ W SW W SW WB SWViburnums Excellent + W SW W SW WB SWShrub dogwoods Excellent + S SW S SW B SBuffalo-berry Good W SW W SW SWStaghorn & smooth Good W S W S B Ssumacs
Short shrubs (Nesting sites, food, cover near ground)
Common chokecherry Excellent ++ S SW S SW SB SWChickasaw plum Excellent + S SW S SW S SWSargent crabapple Excellent + W S W S WB SCotoneaster Good S S S S S SSnowberry Good–Excel W SW W SW B SW
1 Bold letters or ++ indicate an especially good wildlife feature.
2 Several plants in this list have a variety of species or cultivars, and some may have features that differ from those indicated.Also, there may be good plant selections for your area that are not included.
23
ally do not use windbreaks, especially in winter,unless a food source lies nearby. Adjacent crop-lands, such as cornfields, which have wastegrains and interspersed weed seeds, make a goodfood source for ring-necked pheasants, north-ern bobwhites, mourning doves, and others.Avoid autumn plowing of such croplands wherepossible and consider using cropping systems suchas no-tillage that leave ground cover. Old fieldhabitats or water sources near windbreaks canprovide habitat requirements for some species.
Shelter from Predation—Escape CoverWindbreaks provide escape cover and refuge formany wildlife species. Pheasants often stay nearwindbreak cover while feeding in adjacent areas,where, during midday loafing periods, they findrefuge from people and overhead predators. Ingeneral, wider shelterbelts having a good veg-etation layer near the ground offer better escapecover than do narrower and open belts. Whenplanning wildlife escape cover, consider the sur-rounding land use. Where no trees or perchespresently exist, introducing tall deciduous wind-break trees may attract avian predators. In mostsituations, hawks and owls are welcome becausethey eat pest rodents and inspire joy and awe inmany who watch them. However, where enhanc-ing pheasants, quail, or partridge is the primarywildlife goal, choosing shrubs, or moderately-sized trees may be the better alternative.
Shelter from WeatherShelter from the wind is a critical aspect of wild-life survival in winter. An animal maintainswarmth by avoiding exposure to the wind, ide-ally in a warm sunny spot, and by fluffing feath-ers or fur coats. Food is vital because it is the basicsource of all body heat. An animal must balancethe need of finding food against the increasedexposure to wind when foraging. Locating shrubson leeward rows allows animals to receive sunwithin the shrub row and to remain hidden frompredators. Evergreen rows windward of the shrubrows provide protection from cold winter winds.
indbreak Species andMature CharacteristicsSpecies are categorized in Table 3 as:
Shrubs—The species commonly used for thefirst rows in windbreaks and for low, dense,single row plantings for yard protection andsnowdrift control.
Deciduous trees—The species used for theremaining rows of windbreaks where evergreensdo not grow well and for single-row plantingswhere height is needed.
Evergreens—The species that ordinarily pro-vide a selection for at least one row in each wind-break. In areas where they do well, evergreensmay be used for the entire windbreak and forthe new twin-row plantings.
Use Table 3 as a guide. Consult with profession-als in your local area for species expertise thatmay override the general recommendations inthis table.
Nursery StockNearly all windbreaks and other farm treeplantings start with seedling-size plants. Theprincipal reason is to keep the root-to-shootratio in balance. The root-to-shoot ratio is thenatural proportion of the top to the roots. Largestock or even potted or balled and burlap stockhas had its root-to-shoot ratio altered drastically.The altered root-to-shoot ratio is commonlydeficient in roots for the aboveground leaf area.Drought damage is common with trees andshrubs in this condition. Small-size plants nor-mally survive better than large-size plants whentransplanted because of the more equal shoot-to-root ratio. In other words, a smaller tree losesless moisture than a large tree, in proportion toits ability to supply moisture through its rootsystem.
Small-size conservation stock also is less expen-sive than the larger landscape stock used forhorticultural purposes. When using small plants,
W
24
your nursery, transportation expenses, and plant-ing costs are only a small fraction of what theywould be for large plants. For these reasons, youwill save by buying nursery stock on a per 100or per 1,000 basis.
Common seedling types (called stock type) arebare root and plug. Bare root trees are grown ina seedbed, usually outside. They are lifted andsold in bundles—with bare roots. Evergreen seed-ling trees grown in a greenhouse are called“plug” stock, because they are normally grownin plastic foam blocks filled with potting soil.The tree is pulled from the block and trans-planted with potting soil still attached to theroots. Plug seedlings are more expensive thanbare-root trees but often result in a higher sur-vival rate. Plug sizes vary. Generally, a 10- to 20-cubic-inch plug for evergreens is recommendedfor windbreak plantings.
Individually potted trees are not suited for wind-break use because of their restricted root sys-tems. These trees are best used for horticulturalpurposes.
You can obtain planting stock from state or fed-eral nurseries, commercial nurseries or by startingyour own cuttings. Ask for a list of commercialnurseries from your county Extension agent orUSDA-NRCS district conservationist. Some SoilConservation Districts specialize in supplyingstock for farm plantings. They often have speciesnot available from the state nurseries.
Nonrooted CuttingsThe following trees and shrubs can be grownfrom cuttings: golden willow, black willow, pop-lars, common lilac, and common privet (Figure32). If you decide to use your own cuttings fromestablished trees, follow these suggestions:
• Make cuttings in late winter before newgrowth starts. Cut last year’s new growth.
• Make cuttings long enough to contain fiveto six buds. Leave one bud near the top ofthe cutting.
Figure 32. If your cuttings come from one parenttree, they will usually result in very uniform wind-break rows as illustrated here.
• Store cuttings where it is cool and moist.Refrigeration is ideal.
• Plant in spring after the danger of frost ispast.
• Plant the cutting so that only 1–2 buds areabove the soil surface.
• Pack the soil firmly around cuttings.
• Use cuttings only on irrigated land or on siteswith a good natural supply of moisturethroughout the growing season. Soil mustbe kept moist for cuttings to root. Soil sur-face mulches are advantageous on coarse-textured soils. Rooting hormones are notrequired for success in growing cuttings ofthe species mentioned earlier.
25
Site Preparation
Prepare a clean, firm seedbed for your tree plant-ing because good ground preparation conservessoil moisture. Some cropland and pasture siteshave compacted underlying soil layers which areimpenetrable to tree roots. Check for these hardpans. If they are within 18 inches of the surface,plan to rip the tree planting rows to at least a24-inch depth. This will aid in long-term wind-break survival and growth. Shallow disking orharrowing just before planting is adequate oncultivated land without weed problems. For areaswith perennial grasses or weeds, use summerfallow, then disk or harrow before planting time.After disking or harrowing, roll the ground tobe sure the soil is firm (Figure 33).
Care of Trees before PlantingDo not allow tree roots to dry out or expose themto warm temperatures from the time the treesarrive until they are planted. Exposure of rootsystems to drying conditions—sun or wind—isthe cause of many planting failures. If plantingis possible within a week after you receive yourtrees from the nursery, you may leave them inthe original package for transporting to theplanting area (Figure 34).
Store the package in a cool place. Refrigeratedstorage is ideal, but covering packaged seedlingswith snow or space blankets in a shaded loca-tion will keep them in good shape for severaldays. Ideal temperatures are 34°F to 38°F with95% humidity.
If you must delay planting and refrigerated stor-age is not available, unpack and “heel” in trees.Follow these steps:
• Dig V-shaped trench in a moist, shady place.
• Break bundles and spread out evenly, threeto four trees thick.
• Fill in loose soil and water well.
• Complete filling in soil and firm withhands.
Figure 33. Excellent site preparation is necessary forsuccessful windbreak establishment.
Figure 34. When planting seedlings, keep rootscovered with wet material such as peat moss.Do not submerge the roots in water.
26
Site preparation is the foundation of tree
planting. Without it, all your tree plant-
ing efforts may be for naught.
We strongly suggest the use of a tree-plant-
ing machine. Its use will result in better
survival and better initial growth.
Planting the TreeYou may use several methods and tools to planttrees. Machine planters usually are the best alter-native on flat, well-prepared soil if you havemany trees to plant. However, hand plantingusing a spade or shovel is still a popular method.Whatever method you use, follow these instruc-tions closely:
Hand Planting Techniques
• Make the hole deep enough for all roots.
• Cut long roots back to 10 or 12 inches.
• Remove one tree at a time from bucket onlyafter hole is ready for the tree.
• Keep foreign matter (leaves, sticks, rocks, anddry soil) out of hole.
• Place all tree roots in a downward position.
• Place tree in center of hole.
• Hold treetop upright while working soilaround roots.
• Firm soil around roots by hand while fillinghole, leaving no air spaces. Make sure to usemoist soil.
• Bring soil level to root collar (look for colorchange on stem) above the first roots. Toodeep is better than too shallow.
• Firm soil all around tree by hand to give goodcompaction.
Trees planted in an unsatisfactory manner have littlechance to survive. Take an extra moment with eachtree, and do a good job. (Figures 35 and 36)
barrier fabric, but sunlight cannot, so vegeta-tion will not grow through it. The fabric barrierprovides this protection for at least 5 years. Inthe arid west, we have observed good controlfor up to 10 years (Figure 37).
Weed barrier fabric comes in long rolls 6 feetwide and 300 to 500 feet long. It is also availablein 3- foot and 6- foot squares. The roll productis probably more convenient when using amulch-laying machine. The 6-foot-wide rolls aremechanically installed over the top of seedlingimmediately after planting. An “L” shaped slitis cut at each tree location no larger than is nec-essary to pull seedlings through. Though limit-ing the size of cut is important, make it largeenough to prevent the fabric from rubbingagainst the seedling. It is crucial to pull the seed-lings through immediately on warm days, as theheat generated by the fabric can damage or killtender seedlings.
Figure 35. Planting with a shovel is usually a two-person operation following these steps.
2. Straighten back of holeand insert tree at properdepth.
3. In first packing, fill holehalfway with soil andplace tree in properposition.
4. In second packing, fillthe hole completely,pack with hand andcover surface withmulch of loose soil.
W
4 Adapted from Weed Barrier Fabric Mulch for Tree & Shrub Plantings, Kansas State & Extension Forestry, Kansas State University.
27
We strongly suggest the use of a weed barrier
or “fabric mulch.” Its use will result in better
survival and initial growth.
eed Barrier FabricMulch for Tree and ShrubPlantings4
Weed barrier fabric mulch is a polypropylenegeotextile product having the texture of burlap.The barrier eliminates vegetative competitionwith newly planted trees and shrubs by actingas mulch. It conserves soil moisture by reduc-ing evaporation. Water can penetrate weed
1. Insert shovel verticallywith blade reversed,push handle forward,then pull soil back andout of hole.
Figure 36. Plant trees and shrubs in a satisfactory manner. These drawings show various ways treesshould NOT be planted.The ideal is drawing 12.
‘L’ RootsHole shallow
‘U’ or ‘J’ RootsHole shallow, root
ends often exposedto air
Jammed RootsHole too narrow
and shallow
CompactedRoots
Hole too narrow
Too ShallowRoots exposed,hole too shallow
Too DeepNeedles buried,hole OK, treeposition poor
1 2 3 4 5 6
7 8 9 10 11 12
InadequateTamping
Roots dryinglikely due to
depression left
Planted inRotten Wood
Roots not in dampmineral soil
Planted onMound
Roots apt todry out
Not VerticalTree not plantedvertical to the soil
surface
Air PocketShowing improper
tamping
A SatisfactorilyPlanted Tree
Update:
The Plains states, where land managershave had several years experience with fab-ric mulch, are reporting that the mulchunder shade is not deteriorating after 5years and has caused some problems withtrunk girdling. In older plantings wherethe trunk is tight against the mulch,enlarging the slit is recommended. In newplantings, cutting the initial slit in an“L”-shape instead of straight, can allevi-ate this concern. In the future, look forfabric mulch products guaranteed to breakdown after 5 to 7 years, even under shadeconditions.
We still strongly suggest that you use fabric
mulch in all new windbreak plantings.Figure 37. Weed barrier fabric mulch is a polyprop-ylene geotextile product. We recommend its use inall windbreak applications.
28
Soil
surf
ace
Soil
surf
ace
Application of Weed Barrier byMachineThe basic function of the machine is to lay thefabric and bury the fabric edges. The fabric usu-ally is laid over small windbreak plants just afterthey have been planted. The small plants are bentover under the weight of the fabric. The opera-tor (rider) marks them using a can of spray paint.A person immediately follows the machine, cut-ting a small slit and pulling the small plants upthrough the fabric (Figures 38, 39, 40).
At the end of a roll, dig a trench one shovel wideby one shovel deep just in front of the presswheels. Place the last foot of one roll and thefirst foot of the next roll in the trench and coverwith dirt. This will hold the new roll tight untilthe press wheels and closer disks anchor the nextfew feet of material.
Prepare the site to make the ground surface asfirm and smooth as possible to keep the laid fab-ric close to the soil surface. Close soil contactcontrols weeds and prevents the material fromwhipping in the wind. We recommend puttingas little soil as possible on top of the weed bar-rier. Weed seeds can sprout and grow downthrough the material. Wire staples are availableto hold down the center of the fabric.
Variations are possible on this operational pat-tern. If the plants are large and stiff, the opera-tor may have to slit the fabric as it is tightenedto prevent breakage. The fabric also can be laidprior to planting, with or without pre-dug holes.If the plants are tall or stiff, operators may needto set the tool bar and fabric roll high, then slitthe fabric and pull the plants through as thetractor moves very slowly. However, if you movetoo slowly, you may not get adequate soil cov-ering the fabric edges.
Fabric mulch laying machines are becomingmore common in the Pacific Northwest. Checkavailability for short-term lease by contactingyour local conservation district or USDA ServiceCenter. The personnel at the USDA-NRCS PlantMaterials Center in Aberdeen, Idaho, have devel-oped plans for the manufacture of a weed bar-
Figure 38. Installing fabric mulch in a field windbreak.
Figure 39. Marking the location of each newlyplanted seedling under the fabric mulch.
Figure 40. Cutting fabric mulch to free newlyplanted seedling.
29
rier machine. These plans are available by con-tacting the center at 1691 A South 2700 West,PO Box 296, Aberdeen, ID 83210-0296. Ask forTechnical Note 25, Function and Operation of aMachine to Lay Weed Barrier Material, by Simon-son and Cornforth.
ost Planting Care
weather. If you have water available in the fall,irrigate the evergreens once more after you havehad two hard frosts. This fall watering helps thetrees withstand drying winter conditions.
Weed ControlThe first 2 to 3 years after planting are criticaltimes for young trees. Survival relates directlyto available soil moisture. Weed control is essen-tial. If you do not control weeds, the chances oftree survival are slim. Usually a combination ofcultivation and herbicide treatments results inthe best weed control.
Heavy weed cover robs newly planted trees ofsoil moisture and nutrients. Young trees grownover with weeds or grass may be kept alive byfrequent watering, but the tree growth will usu-ally be disappointing. Since weed control is soessential to the success of any farm tree plant-ing, a plan for appropriate and timely applica-tion of the cultivation, herbicides, or mulch isvital. After the trees are well established, youcan seed grasses in irrigated plantings and sub-stitute mowing for cultivation. In most drylandplantings, the use of fabric mulch is a necessity.This new technology makes it possible to estab-lish and grow trees and shrubs on the mostdifficult sites (Figure 41).
P“Ninety percent of a successful windbreak
is conscientious maintenance,”
Loren St. John, Team Leader,Plant Material Center, USDA-NRCS,
Aberdeen, ID
Although you plan and plant a windbreak toget effective wind protection, some factors willprevent you from achieving your goals unlessyou can give your trees good care. This sectiondescribes commonly needed practices.
IrrigationA good supply of moisture close to the soil sur-face is essential for successful establishment ofnew tree plantings. In our arid regions, drip irri-gation is the best system to use, especially whencombined with fabric mulch. Windbreaks havebeen established on deep loam soils using thefabric mulch but without supplemental water-ing in Adams County, Washington, whichreceives less than 10 inches of annual precipita-tion. Water windbreaks often enough to keepthe trees in active growth all summer. Wateringfrequency depends on soil type, local tempera-ture, and wind conditions. As a rule, water yourtrees once each week during hot weather in theirfirst growing season. During the second andthird seasons, water about once every 10 days.
When you irrigate your trees, leave the wateron long enough to get deep-water penetrationthroughout the root zone. Shallow wateringencourages shallow rooting. Stop watering in thefall 3 weeks before the usual date of first frost,which will help your trees harden off to cold
Figure 41. Rocky Mountain juniper providesexcellent growth under dryland conditions ineastern Washington when fabric mulch is used.
30
CultivationCultivate your windbreak often to control weeds.Cultivate when the weeds are small, less than2 inches in height. Shallow cultivation (2 to 4inches) is best since deep cultivation near thetrees destroys many feeder roots and wastes soilmoisture. Avoid hilling up the soil aroundyoung trees. Covering branches will injure orkill them.
Duck-foot cultivators and spring tooth harrowsare good cultivating tools. Disk harrows are notas good but can be used if carefully regulated.While trees are small, over-the-row cultivatingmay be feasible with side delivery rakes. Putting16-inch flexible tines in a section harrow canmake a good over-the-row cultivator. A dumptype rake fitted with smaller wheels does a satis-factory job.
Hand hoeing may be necessary if you do nothave equipment to get at weeds within the treerows. Special tools are available like the grapehoe and shelterbelt cultivator that swing outfrom the side of a tractor to remove the weedsfrom within the tree rows. Attaching suitabletines to an old mower bar can make a usablein-row cultivator.
Cultivate irrigated windbreaks for at least 3 years.After the trees are well established, you may seeda cover of low grass to help keep down the weeds.The best practice for dryland windbreaks is tokeep your planting clean cultivated as long aspossible.
Herbicide UsageHerbicides are effective chemical tools for con-trolling unwanted weeds. Some are safe to usein established plantings, while others shouldonly be used as “directed sprays” on the weeds.Always follow label directions. If herbicidesare not applied according to label directions,damage to your trees or soil may result. Manydifferent herbicides are available; check with yourExtension county agricultural educator for properrecommendations. Recommended herbicides vary
depending on the tree species in the windbreakand the target weed species. The species you wishto protect (site) must appear on the productlabel, the pest species to control should alsobe listed.
FertilizersTrees usually make good growth without anyfertilizer on agricultural soils. However, mostestablished trees respond favorably to nitrogenor other limiting elements after growing for twoseasons or more. In general, do not fertilizeyoung trees at the time of planting unless theplanting site is extremely low in fertility. Theroot systems of young trees are susceptible todamage by fertilization.
Windbreak owners have no single indicator totell them if trees need fertilizer. Some suspectedlow fertility conditions or symptoms also couldbe caused by disease, poor root system, inap-propriately applied herbicides, or other prob-lems. These symptoms include leaves of smallerthan usual size, presence of light green or off-color foliage, dead twigs on the ends of branches,very short elongation of branches during thegrowing season, and general lack of thriftinessor vigor. If any of these symptoms are present,the tree may benefit from fertilization. Similarly,if the tree has been physically injured or hassustained severe defoliation by insects, disease,or hail, fertilization may be helpful during therecovery period.
While windbreak trees require nitrogen, phos-phorus, and potassium in the largest amounts,all windbreak trees and shrubs require severalother nutrients. These include calcium, magne-sium, sulfur, chlorine, iron, manganese, copper,boron, zinc, and molybdenum. Three numberson all fertilizer packages represent nitrogen,potassium, and phosphorus concentrations ina formulation. For example, 20-10-10 indicatesthat the formulation contains 20% N, 10% Pand 10% K. Most soils contain adequate amountsof these elements, except for iron, which is fre-quently deficient. To confirm fertility needs,complete a soil test for the site.
31
Iron ChlorosisSpecific foliage discoloration may signal somenutrient deficiencies. Prolonged nutrient defi-ciency will result in poor vigor, making the treevulnerable to disease and insect attacks, oftenresulting in the tree’s death.
The most commonly occurring discoloration ofleaves is the development of a yellow or lightyellow-green color. If this discoloration occursin the areas between the leaf veins, it usuallyleaves the leaf veins and leaf tissue near theveins a darker green color. This condition, called“chlorosis,” is associated with a lack of availableiron. The chlorosis may occur only on part ofthe tree, such as a single branch, or may affectthe entire tree. Apply iron-rich fertilizers if thissymptom is present. Chelated iron formulationsare usually the best. The practicality of this rec-ommendation depends on whether the symp-tom appears on just a segment of the windbreakor an on entire row. One alternative is to knowthe soil situation during the planning stage andavoid selecting trees or shrubs most susceptibleto chlorosis.
Timing Fertilizer ApplicationsFor greatest value to the tree, apply fertilizer inthe spring as soon as the soil is frost-free or applyon top of a late season snow layer. Fertilizerapplied in early spring is available for the tree touse as soon as growth resumes. Since root growthwill begin before leaf development, apply fertil-izers as early as possible.
Do not fertilize trees in mid-summer becauseirrigation is not usually sufficient to avoid foli-age “burning.” Also avoid late summer applica-tions because they may produce new growthtissue that will not harden off sufficiently beforefall freezes, resulting in winter injury.
Fertilizer QuantitiesIn dryland plantings receiving less than 16inches of annual precipitation, you can easilydo serious damage to evergreens with nitrogen.Use no more than 40 pounds nitrogen per acre.In irrigated plantings, you can apply 80 poundsnitrogen per acre to established trees. For areadeterminations, include only the area undertrees and shrubs, not the area between the rows.Be sure to keep the amount of fertilizer youapply in line with the amount recommended.For example, if the recommendation is 40pounds nitrogen per acre, this corresponds to200 pounds per acre of a 20-10-0 fertilizer.
rotectionLivestock, poultry, mice, gophers, rabbits, deer,porcupines, insects, diseases, and herbicide driftcan be real enemies of farm tree plantings. Youcan control the threat from livestock and poul-try by fencing them out. You will be wise to fencebefore you plant. If you plant trees next tomeadow, hay land, sagebrush areas, or roadrights-of-way, you may have to combat mice,gophers, or rabbits (Figures 42 and 43).
P
Figure 42. Livestock can damagethis excellent windbreak in shortorder by rubbing, trampling, andcompacting the soil.
32
Clean cultivation helps keep out mice andgophers but does not provide complete assur-ance against damage from them. Mice andgophers move into clean plantings under snowcover. You may choose screen wire or hardwarecloth cylinders to protect small trees, as fenc-ing can prevent damage from rabbits androdents. Sometimes live trapping or poisons arethe only options.
Examine your windbreak periodically in late fall,winter, and early spring for signs of insect ordisease damage. If you discover a pest problemin your tree planting and do not know how tocontrol it, ask the Extension agricultural agentin your county for recommendations.
What appears to be disease damage in farm treeplantings frequently results from the improperuse of herbicides. A cause of such damage isrepeated occurrences of herbicide drift in fieldsor along roads. Both deciduous trees and ever-greens are affected, but some species are muchmore susceptible than others. As a group, ever-greens in the dormant stage (after bud set) aremore resistant to herbicide damage than aredeciduous trees in full leaf. However, pines arevery susceptible to herbicide drift during activegrowth in the early spring. New growth onevergreens may wilt, with browning of theneedle tips developing later. Twisted, malformedleaders or tree deaths often result.
In deciduous trees, the most serious herbicidedamage usually occurs in spring or early summerwhile the new leaves are still tender. Commonsymptoms are crinkling or curling of the leaves,fading of the green color between the leaf veins,and stunted leaf and twig development. Insevere cases, all new growth on trees may bestunted or deformed and killed.
Soil-active herbicides are not recommended formost windbreak plantings, as the chemicals canbe quite damaging to trees with shallow rootsystems, especially blue and Norway spruces.Herbicide symptoms on these species include arandom pattern of purplish colored needles inthe tree crown, followed by defoliation.
If your windbreak has herbicide symptoms,minimize tree stress by frequent irrigation, byfertilizing the following spring, and by control-ling aphid and scale insects. In most cases, thetrees will survive from a single herbicide appli-cation. Death is most always attributed torepeated herbicide contact.
enovation of Old PlantingsTrees in many old windbreaks and other farm treeplantings show sparse crowns, dying branches,and other signs of low vigor (Figure 44). Over-
Figure 43. Windbreak damage caused by livestockgrazing.
R
Figure 44. Renovation of old windbreak usingeastern redcedar in the Great Plains region. RockyMountain juniper is the preferred species in thePacific Northwest for a similar application.
33
crowding often causes these conditions. Oldplantings commonly were made with spacingtoo close to give the trees room to grow. Thetrees probably did well during their early years,but long before reaching maturity, they werecrowding each other severely. Growth rateslowed down, vigor decreased, and the treesbecame more susceptible to disease, insects,drought, and herbicides. Often the older wind-break has grown less effective due to the decreasein density, especially near the ground.
In an old planting, thinning or cutting out theweaker trees helps strengthen the remainingones. Remove every other tree within the rowor, if some rows are overtopped or almostentirely dead, remove them completely. Fertil-izers aid in rejuvenating old plantings, particu-larly black locust and Siberian pea shrub.
Enlargement plantings are a form of windbreakrenovation. If the main windbreak is not tooweak, simply add new rows to it on either thewindward or leeward sides, space permitting. Useevergreen trees or dense shrubs to increase thedensity near the ground for improved windreductions and snow catchments (Figure 45).
Rejuvenation options are often site specific. Seekhelp from your local Extension agent or USDA-NRCS specialist for rejuvenation alternatives(Figure 46).
Figure 45. Twin rows of eastern redcedar areoften used to renovate older windbreaks in theGreat Plains region. Rocky Mountain juniper isthe preferred species in the Pacific Northwestfor a similar application.
Figure 46. Renovated windbreak protecting thisclean cultivated field.
Figure 47. This windbreak is providing benefits justa few years after establishment.
A Final WordIn the past, windbreaks were thought to be con-servation practices that would provide benefitsway off in the future. This notion is no longertrue as new establishment technologies, coupledwith better tree and shrub species, result ineffective barriers in just a few years, even on theharshest sites in the arid regions of the PacificNorthwest (Figure 47).
34
ources of AdditionalInformationYou may obtain additional information, advice,or planning assistance from any of the following:
• Washington State University, University ofIdaho, and Oregon State University ExtensionServices: located in virtually every county ofthe three states.
• District Conservationist, or a forestry oragroforestry specialist with the USDA.
• Natural Resources Conservation Service,located at the USDA Service Center.
• The local soil and water conservation district.
ources of Planting Stock
State or Federal NurseriesEach of the three Pacific Northwest states has apublicly owned nursery established to providetree and shrub planting stock to rural landown-ers at reasonable costs. Tree and shrub speciescommonly used for windbreak plantings can bepurchased from these nurseries:
• IdahoUniversity of IdahoForest Research NurseryPO Box 441137Moscow, Idaho 83844-1137(208) 885-3888
• WashingtonDepartment of Natural ResourcesWebster Forest Nursery9805 Blomberg St SWPO Box 47017Olympia, WA 98504-7017(360) 753-5305—Toll Free: (877) 890-2626
• OregonOregon Department of ForestryD. L. Phipps Nursery2424 Wells Rd.Elkton, Oregon 97436(541) 584-2214
Contact each nursery for ordering and priceinformation. Planting stock purchased fromthese public nurseries has a few restrictions:
• Trees may not be planted inside the limitsof incorporated towns or cities.
• Trees may not be used for ornamentalpurposes.
• Trees may not be resold with roots attached.
• Trees may not be planted outside the statein which they were ordered.
Commercial NurseriesMany commercial nurseries produce seedling-size trees for farm and forest plantings. They fre-quently have species or varieties of trees andshrubs not available from the public nurseries.There is no restriction on the use of plantingstock purchased from a commercial nursery. Pur-chase trees only from nurseries that providequantity prices, as individual potted trees wouldbe very expensive. Ask your Extension countyagent or USDA-NRCS district conservationist fora list of commercial nurseries that produce seed-ling trees for farm plantings.
Soil Conservation DistrictsA third source of tree stock is Conservation Dis-tricts. Conservation Districts often purchasetrees from commercial nurseries in large quan-tities. The districts then resell the trees to indi-viduals as a service. Contact your local districtor USDA-NRCS office for details.
S
S
35
ndividual SpeciesCharacteristics: ShrubsSiberian pea shrub (Caragana arborescens)
A dense, attractive, many stemmed shrub.Grows rapidly. Has long life, adapts to a widerange of soils and elevations. Generallyinsect and disease free. Sprouts from rootcollar only. Good for dryland or irrigatedplantings. Reaches full size on irrigated landin 5 to 7 years, on dryland in 10 to 12 years.Can be trimmed to make an excellent pro-tective hedge. Forms a superior windbreakshrub adaptable to the whole region. It isweakened by repeated 2,4-D exposures.
Skunkbush sumac (Rhus trilobata)A dense, attractive, many stemmed shrub.Grows well on very droughty sites. Adapts toa wide range of soil and salinities. It has theability to grow in dryland conditions havingas little as 10 inches of annual precipitation.Growth rates are much better under drip irri-gation. The deep green summer foliagechanges to bronzy red in fall, and clusters ofred fruit develop in late summer. Fruit pro-vides excellent fall and winter food as softmast for birds. Produces light yellow flowers.
Common lilac (Syringa vulgaris)Very dense. This long-lived shrub has a lowto medium growth rate. It adapts to a widerange of soils and elevation. Sprouts heavily,mainly at the root crown, but spreads slowly.Makes excellent hedge or shrub row in wind-break. Has high aesthetic value. Occasionallybecomes infested with scale insects,extremely sensitive to 2,4-D. Has high resis-tance to drought and cold.
Amur or freedom honeysuckle (Lonicera spp.)Attractive, globe shaped, many stemmedshrub. Bears numerous pink or white flow-ers. Red fruit holds on until fall. Provides goodwildlife food and cover. Improved varietiesnot commonly subject to insect or diseaseproblems. Does well on most soils.
Common privet (Ligustrum vulgare)An extremely dense, attractive shrub produc-ing medium to rapid growth. Needs well-drained soil. A nearly ideal plant for low,single-row windbreaks, as well as the shrubrow in multiple-row plantings.
Nanking cherry (Prunus tomentosa)An attractive, upright shrub with a fastgrowth rate. Produces abundant, edible fruitthat makes good jelly. Fruit is retainedthroughout winter and makes good wildlifefood. Some hybrid varieties grow to 10 feettall. Has fair to good windbreak qualities. Fewinsect or disease problems. Do not plant nearcherry orchards because it is an alternate hostto Western X cherry disease. Does not do wellin the coldest areas.
Peking cotoneaster (Cotoneaster acutifolia)Similar to Nanking cherry. Will grow onsevere sites. Moderate growth rate. Withstandsdrought well. Produces abundant fruitretained throughout the winter. An excellentspecies for adding wildlife value to a wind-break. Few insect or disease problems.
Mugho pine (Pinus mugo)An attractive, compact evergreen shrub withmoderate growth rate. Does best on fertile,well-drained soils. Performs best as a wind-break shrub at elevations below 4,500 feetas winter burning is a problem above thiselevation.
ndividual SpeciesCharacteristics: DeciduousTreesGolden willow (Salix alba var. vitellina)
A medium-size tree having good growth formfor windbreak use. Bright yellow to orangecolored young branches make it attractive inwinter. Grows rapidly; adapts to a wide rangeof soil and moisture conditions. Sprouts only
I
I
36
from roots and does not spread from runners.Subject to severe damage from scale insectsand aphids. Use for dryland plantings only ifsupplemental moisture is available. Excellentin the Palouse. Poor for firewood.
Black willow (Salix nigra)Grows very rapidly under irrigation. Formsbroad, moderately dense globe-shaped crown.Usually produces several stems from nearground level. Serves well as a middle row inwindbreaks. Not very suitable for single rowplantings because of its low, wide spreadingbranches. Has performed well in localitieshaving salty soils and high water tables,where establishment of other species wasdifficult. Subject to damage by scale insects.Poor for firewood.
Black locust (Robinia pseudoacacia)Has rapid growth rate. Forms moderatelydense crown. Tolerates very hot climates.Adapts to a wide range of soil conditions butdoes not withstand water logging. Locust boreris a serious insect problem in young trees.Not recommended for ditch bank or fencerowplantings because injured roots produce thick-ets of sprouts. Requires little maintenanceonce it is established. A widely used tree pro-viding good shade, aesthetic and wildlifevalues. The locust borer makes it impracticalfor new plantings. Excellent for firewood.
Honey locust (Gleditsia triacanthos var. inermis)Medium to tall tree. Fairly drought resistant.Withstands alkaline soils well. Attractivezigzag twigs, fine textured leaflets. Two- to four-inch thorns. Fruit is a large 12-inch (maxi-mum) pod. Winter injury on harsh sites.Good for firewood.
Hybrid poplar (Populus x spp.)Grows rapidly. Has dense crown and goodform. Does best under irrigation but performswell in dryland plantings receiving 25 inchesor more annual precipitation. Provides quickprotection. Suckers develop from injuredroots. Do not plant near field drains or alongirrigation ditches. Susceptible to poplar andwillow borer. Much clonal variation; purchase
stock from a source field tested in your area.(Note: There are many hybrid poplars. Be sure toget the correct variety for your area.) Poor forfirewood.
Green ash (Fraxinus pennsylvanica var. lanceolata)A deep-rooted, long-lived tree having a dense,symmetrical, and attractive crown. Growthmay be slow at first but becomes moderateto rapid after tree is established. It will beovertopped by more rapidly growing trees,such as black locust and Siberian elm, ifplanted too close to them. Sprouting is neg-ligible. An excellent tree for ditch bank andfence row plantings. It is more winter hardyand salt tolerant than black locust. It is dam-aged by herbicide sprays but is more resistantthan Siberian elm. Subject to damage by scaleinsects and aphids. Excellent for firewood.
Lombardy poplar (Populus nigra var. italica)Overplanted throughout the Pacific Northwest,where it is not generally recommended. Growsvery rapidly, reaching 40 feet in 12 yearsunder favorable conditions. Has very narrow,though fairly dense, crown. Makes good middlerow where fast growth and extra windbreakheight are desired. Subject to some cankerdiseases and heart rot, especially if trees havebeen damaged by topping, fire, or other causes.Windfirm unless diseased. Susceptible topoplar and willow borer. Short lived. Poor forfirewood.
Russian olive (Elaeagnus angustifolia)Do not use this tree along ditch banks, in wetpastures, or along streams. A small tree withdense, attractive crown. A superior tree forwindbreak, wildlife, and aesthetic values andfor drought resistance. Makes a dense hedgewhen clipped. Its spiny-tipped twigs make adense planting an almost impenetrable barrier.Considered one of the best deciduous speciesfor dryland plantings in the region. Growsrapidly, especially on good soil with amplemoisture. Adapted to a wide range of soils.Sprouting is negligible, but it spreads by seedwhere soil moisture is adequate. More resistantto spray damage than other deciduous speciesbut not as resistant as dormant evergreens.
37
ndividual SpeciesCharacteristics: Evergreens
Rocky Mountain juniper(Juniperus scopulorum)
Excellent success when planted using the newfabric mulch. Achieves medium to rapid growth.Forms very dense, symmetrical crown. Adaptedto wide soil variations. Tolerates high watertable. A superior small windbreak tree for thisregion. Bare-rooted planting stock is difficultto establish on dry land but does well onceestablished. Subject to damage by spider mites;sometimes a host to cedar apple rust.
Eastern redcedar or Virginia juniper(Juniperus virginiana)
Has moderate to fast growth rate. Similar inappearance to Rocky Mountain juniper andgenerally as adaptable. It is easily establishedexcept on very dry sites and at high elevations.Well liked for single row screens. Subject toattack by cedar apple rust. Do not plant nearapple orchards.
Northern white cedar (Thuja occidentalis)Commonly called Arborvitae. Moderate growthrate. Forms very dense, attractive crown. Holdslower branches well. Makes a dense single-row windbreak or leeward row in a multiplerow planting. Survives well under irrigationwhere soils are not highly saline. No knowninsect problems; is susceptible to Phytophthoracinnamomi. Has not been widely used, butexisting plantings indicate it is a good treefor many localities. Well-liked in Oregon forsingle-row screens and windbreaks.
Austrian pine (Pinus nigra)Has medium growth rate. Develops very densesymmetrical crown for a pine. Holds lowerbranches well. An excellent tree under irri-gation but sometimes fails in low rainfall dry-land plantings after 10 to 12 years. If plantedwithout supplemental watering in localitiesreceiving less than 20-inch annual precipita-tion, it needs a deep, fertile soil with goodmoisture holding capacity. Considered anexcellent species for the Columbia Basin.
Ponderosa pine is preferred in Wasco, Gilliam,Sherman, and Morrow counties, Oregon.Usually remains free of insect and diseaseproblems. Susceptible to iron chlorosis. Mod-erate for firewood.
Incense cedar (Calocedrus decurrens)Recommended for western Oregon in theWillamette and interior valley regions only,but not to be planted within a mile of com-mercial pear orchards, as it is the alternatehost for Northwest pear rust. Medium to goodgrowth on better soils. Develops a nice sym-metrical crown that holds lower brancheswell. It can grow in many soil types includ-ing rhyolite, sandstone, and serpentine. Tol-erates dry summer conditions. Free of majorinsect and disease problems when tree vigoris maintained.
Scotch pine (Pinus sylvestris)Has rapid growth rate. Crown density is usu-ally medium. Lower branches shade out anddie if they do not get full sunlight. Adapts to awide variety of soil conditions. Withstandspermanently moist soil conditions better thanponderosa pine. Susceptible to a variety ofneedle diseases in wet climates. Sequoia pitchmoth can be a serious problem in westernOregon if lower branches are pruned in thegrowing season. A widely used tree for wind-breaks. Many strains of Scotch pine are avail-able. Some have poor form. Spanish burgovariety does well in Idaho. Moderate for firewood.
Blue spruce (Picea pungens var. glauca)Growth rate is unusually slow for first 5 yearsafter planting but has medium growth rateafter that. Crown is very dense with attractivepyramidal form. Traps and holds snow well.Makes an excellent windbreak species in mostof the region. Color varies from green to blue.Sometimes it is difficult to establish. Subjectto damage by spider mites, scale insects, andspruce gall adelgid.
Norway spruce (Picea abies)Grows rapidly. Develops a very dense crownthat extends to the ground unless the base ofthe crown is in heavy shade. Moisture and
I
38
soil fertility requirements are higher than forthe pines. Does fairly well in dryland plantingsif soil is deep and fertile. Subject to spidermite and spruce bud scale damage. Some-times becomes stunted in growth due to zincdeficiency. Spruces are poor choices for fire-wood.
Ponderosa pine (Pinus ponderosa)Has moderate growth rate. Crown is sym-metrical and fairly dense. Needs full sunlightfor best development. Lower branches shadeout and die under close spacing. Adapts wellto a variety of soil conditions but must havegood drainage. Withstands hot, dry sites well.Can be damaged or killed by too much irri-gation. Generally free of insect and diseaseproblems. Many consider this the most reli-able evergreen for windbreaks. Highly pre-ferred in Oregon and in much of the Colum-bia Basin. Moderate for firewood.
Douglas-fir (Pseudotsuga menziesii)Generally not a good windbreak tree in thearid areas of the PNW. Has medium growthrate. Crown is dense and symmetrical. Needsa well-drained soil. More difficult to estab-lish under irrigation than Scotch pine orNorway spruce. Sometimes difficult to estab-lish on grassland soils. Growth is generallyslow without supplemental watering in areasreceiving less than 18 inches annual precipi-tation. Good for firewood.
Lodgepole pine (Pinus contorta)Generally not a good windbreak tree in thearid areas of the PNW, but commonly foundalong the coast in very sandy soils. Alsoknown as shore pine. Has slow growth rate.Crown is dense on poor sandy soils and thinon better sites. Tolerates salty atmosphere andperiodic flooding as well as any conifer. Fairto poor for firewood.
39
uggested ReadingAtchison, Robert L., and Leah B. Riche, 1996. Weed Barrier Fabric Mulch for Tree and ShrubPlantings. Kansas State University Cooperative Extension Service, MF-2216.
Boehner, Patricia, and James Brandle. Windbreak Establishment. University of NebraskaCooperative Extension, EC 91-1764-B.
Brandle, James, Tom Wardle, and Gerald Bratton. 1992. Working Trees for Carbon: Windbreaksin the US. USDA-National Agroforestry Center. Available from www.unl.edu/nac.
Brandle, James, and H. Doak Nickerson. Windbreaks for Snow Management. University ofNebraska Cooperative Extension, EC 96-1770-X.
Brandle, James, and Laurie Hodges. Field Windbreaks. University of Nebraska CooperativeExtension, EC 00-1778-X.
Brandle, James, and Sherman Finch. How Windbreaks Work. Nebraska CooperativeExtension, EC 91-1763-B.
Garrett, H.E., W.J.Rietveld, and R.F. Fisher, Eds. 2000. North American Agroforestry: AnIntegrated Science and Practice. American Society of Agronomy. 402p.
Josiah, Scott J. 2000. Discovering Profits in Unlikely Places: Agroforestry Opportunities forAdded Income. University of Minnesota Extension Service, BU-7407-S.
Kuhn, Gary, James Robinson, Bruce Wight, and Lyn Townsend. 1996. USDA-NRCS,Agroforestry Tech. Note 1.
Quam, Vernon, LaDon Johnson, Bruce Wight, and James Brandle. Windbreaks for LivestockOperations. University of Nebraska Cooperative Extension, EC 94-1766-X.
Quam, Vernon, James Brandle, and Teresa Boes. Windbreaks in Sustainable AgriculturalSystems. University of Nebraska Cooperative Extension, EC 91-1772-X.
Stange, Craig, and James Brandle. Windbreak Management. University of Nebraska CooperativeExtension, EC 96-1768-X.
Stange, Craig, Jon Wilson, James Brandle, and Mike Kuhns. Windbreak Renovation. Universityof Nebraska Cooperative Extension, EC 98-1777-X.
Tyndall, John, and Joseph P. Colletti. 2001. Air Quality and Shelterbelts: Odor Mitigationand Livestock Production, A Literature Review. USDA National Agroforestry Center SponsoredResearch Project, Forestry Department, Iowa State University.
Wight, Bruce, Teresa Boes, and James Brandle. Windbreaks for Rural Living. University ofNebraska Cooperative Extension, EC 91-1767-X.
______, Windbreaks for Conservation. 1969. USDA-Natural Resources Conservation Service,Agricultural Information Bulletin No. 339, 25 p.
_____, 2001. NAC Free Informational/Educational Agroforestry Materials—NAC PublicationList. Summer 2001. Available from www.unl.edu/nac
_____, 1999. Living Snow Fences. USDA-NRCS, Idaho State Office, Boise, ID.
S
40
Pacific Northwest extension publications are produced cooperatively by the three Pacific NorthwestLand-Grant universities: Washington State University, Oregon State University, and the Universityof Idaho. Similar crops, climate, and topography create a natural geographic unit that crossesstate lines. Since 1949, the PNW program has published more than 550 titles, preventingduplication of effort, broadening the availability of faculty specialists, and substantially reducingcosts for the participating states.
Pacific Northwest Extension Publications contain material written and produced for publicdistribution. You may reprint written material, provided you do not use it to endorse a commercialproduct. Please reference by title and credit Pacific Northwest Extension Publications.
Copyright 2003 Washington State University.
Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, byWashington State University Cooperative Extension, Oregon State University Extension Service,University of Idaho Cooperative Extension System, and the U.S. Department of Agriculturecooperating. Cooperative Extension programs, activities, materials, and policies comply withfederal and state laws and regulations on nondiscrimination regarding race, sex, religion, age,color, creed, national or ethnic origin; physical, mental, or sensory disability; marital status, sexualorientation, and status as a Vietnam-era or disabled veteran. Washington State UniversityCooperative Extension, The Oregon State University Extension Service, and University of IdahoExtension are Equal Opportunity Employers. Evidence of noncompliance may be reported throughyour local Cooperative Extension office. Trade names have been used to simplify information; noendorsement is intended. Published January 1953. Revised February 2003. $8.00. PNW0005
Order information:Washington State University Cooperative ExtensionWeb http://pubs.wsu.edu Fax 1-509-335-3006 Toll-free phone [email protected]
Oregon State University Extension ServiceWeb http://eesc.orst.edu Fax 541-737-0817 Phone [email protected]
University of Idaho ExtensionWeb http://info.ag.uidaho.edu Fax 208-885-4648 Phone [email protected]