Windbreak Trees
Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist
It's been said that the Tri-Cities is a windy area. You betcha! You’ll get no argument from most area residents. Wind erodes our soil and leads to nasty dust storms. Winter winds can increase a home's heating costs by 10 to 40 per cent. Wind can also be just plain annoying. You can't stop the wind, but you certainly can slow it down with strategically placed trees and shrubs ... windbreaks.
"A windbreak is a planting usually of both trees and shrubs that is designed and established to reduce the undesirable effects of strong winds," says Don Hanley, WSU Extension Forester. Early settlers in the treeless areas of Washington and the rest of the Northwest needed trees to provide much needed shade and protection from the wind. Farmers planted fast-growing species of trees in a simple one to six row design. Single species of trees, such as eastern cottonwood, black locust, and Lombardy poplar, were planted fairly close together. Not all these windbreaks were successful ... improper placement or poor selection of the tree species meant a failure to obtain the goal of diminishing the wind.
Things haven't changed much since the days of those early pioneers. Farmers and homeowners are still planting windbreaks and still having limited success. The main reason for the failure of windbreak plantings is that many are not given adequate care to get them off to a good start. Plantings often succumb to a lack of water, competition from weeds, damage by livestock, mechanical injury from mowers and other equipment, and careless use of weed control chemicals. Windbreak plantings are just like any other landscape planting, the trees need care and attention to be able to live and grow.
While the pioneers had to guess what trees to use and where to plant them, scientific research has revealed the proper design, location, and types of trees that will provide the most effective windbreaks.
Planning
These are the things you should consider when planning your windbreak:
- The location that the windbreak will be most effective.
- Do you have enough space for a windbreak? How many rows will you plant? The most effective windbreak has five rows of deciduous and evergreen trees and shrubs.
- What species are best adapted to the area and your situation?
- Is there irrigation available to provide them with the needed water for establishing and maintaining them?
- Will the trees create a problem when they reach their mature size?
Placement
Our local prevailing winds tend to come from the west, but this may vary slightly depending on your situation and topography. A windbreak should be located so that it’s at a right angle to the prevailing winds, or as nearly as possible to a right angle. The closer it is to the right angle, the more effective it will be.
To be effective, the windbreak should be no more than 100 feet from the house. At this distance, trees 35 or more feet tall break and lift the wind currents over the top of the home, You can place the windbreak closer but make sure the trees don’t shade the house.
The windbreak should also extend fifty feet beyond the length of the house and the area you want protected. If you must have gaps in your windbreak rows to accommodate irrigation ditches, paths, driveways, etc., try to make the crossings at oblique angles so you don’t create your own sort of “wind tunnel.”
Number of Rows
Many people usually plant only one-row windbreaks. However, the more rows you plant, the more effective the windbreak. If there is not enough room available for a full five rows, consider four or less rows. Be sure not to crowd the rows though. Crowding slows growth and weakens the plants. Lower limbs of crowded trees tend to die out due to heavy shade. Trees should be staggered between rows.
If there is only room for four rows, the best protection is achieved with a row of dense shrubs, a row of medium evergreens, a row of tall evergreens, and a row of medium evergreens. With three rows you’ll get the maximum protection with single rows of a dense shrub, a tall evergreen, and a medium evergreen. With two rows, you’ll want to use a medium evergreen and a tall evergreen. If you only have room for one row ... use a tall evergreen, such as arborvitae.
Spacing
The spacing between rows should be sixteen feet. The spacing between plants in the rows should be:
Tree/Shrub Type
Multiple-row Windbreaks
Single-row Windbreaks
Dense Shrubs
3
2
Medium Deciduous Trees
9
6
Tall Deciduous Trees
12
8
Medium Evergreen Trees
9
6
Tall Evergreen Trees
12
8
These spacings give the trees and shrubs room to develop full dense crowns before they start growing together.
Another option for design is a twin-row, high density windbreak which can be used when space between the home and planting is limited. With this high density design, the two rows of trees are planted six feet apart and the trees are planted five to eight feet apart within the rows. The same species may be used in the twin row. Additional twin-rows can be placed 25 to 50 feet away, allowing for the planting of gardens between two twin rows. The distance of 100 feet between the house and the windbreak can be reduced. The spacing of the trees facilitates watering by drip irrigation.
Planting
No windbreak will succeed if the plants aren’t planted right. As with any landscape planting, you should prepare the soil first. You may find it easiest to till the soil along the row. Till the soil to a depth of 18 inches, or more if possible. Then dig a trench deep enough to accommodate the roots of the trees. The top of the root ball should be at soil level or just a little above to allow for the soil settling.
Place the trees in the center of the trench or hole so that all the tree roots are in a downward position. Hold the tree while filling the soil back in around the roots. This is probably easiest when done by a team of two people or more. Gently firm the soil around the roots and then water the trees in with a thorough application of water.
Apply a slow release fertilizer at the rate recommended on the label. Don't over-fertilize because the fertilizer salts can damage the young roots of the plants.
You can encourage growth of the trees and shrubs by topdressing with an application of fertilizer each spring just as new growth starts to unfold. Look for an acidifying fertilizer to help lower the pH or alkalinity of the soil. This is most important with evergreens because they generally prefer slightly acid soils. Many local soils are quite alkaline, unless they have been under irrigation for years.
Weeds and grass growing around the trees can impede growth by robbing them of needed nutrients and moisture. A three to four inch thick layer of wood chip or bark mulch will be beneficial in keeping down weed growth and maintaining soil moisture. Mulch the entire root zone if possible, but keep the mulch several inches away from the tree trunk.
The most successful windbreaks are those with live and growing trees. Provide the needed water and care to help the trees establish and thrive. Be sure to provide protection from animal and equipment damage.
Time To Grow
If planned and planted properly, it will only take about three to four years before you start noticing the protection that your windbreak is providing. Within seven years the windbreak should be providing effective protection to you and your home.
For more detailed information contact your local WSU Cooperative Extension office for the bulletin "Trees Against the Wind."
What Types of Plants Do Best In Windbreaks
Early pioneers planted a variety of fast-growing, soft-wooded, short-live tree species, such as Lombardy poplar, willow and cottonwood, for their windbreaks. Many of these fast-growing trees are still recommended and used for modern farm windbreak use. However, homeowners should be aware that most of these are very invasive and have extensive root systems that can be a problem with septic systems, driveways, swimming pools and elsewhere. These species also tend to be short-lived, such as with poplars which start to decline after about fifteen years. The only advantages to using them are that they are inexpensive and they grow quickly. There are better plants that will provide more effective, long-term windbreaks. Here are some:
Deciduous Shrubs
Mature Height (feet)
Crown Height (feet)
Common lilac
10
10
Tartarian honeysuckle
8
7
Common privet
10
8
Nanking cherry
6
4
Tall Evergreen Trees
12
8
Evergreen Shrubs
Mature Height (feet)
Crown Height (feet)
Mugho pine
8
8
Deciduous Trees
Mature Height (feet)
Crown Height (feet)
Fastigiate European hornbeam
35-40
20-30
Fastigiate English Oak
50-60
15-20
Littleleaf Linden
60-80
35-55
Hedge maple
25-35
25-35
Evergreen Trees
Mature Height (feet)
Crown Height (feet)
Arborvitae(Northern White Cedar)
35
20
Scotch pine
40
20
Austrian pine
40
30
Blue spruce
40
25
White fir
30-50
15-30
Nordman fir
40-60
Douglas fir
60
25
Rocky mountain juniper
20
15
Eastern juniper
25
15