In areas with wide expanses of open, flat land, wind may sweep across the surface with a great deal of force. Windbreaks may be constructed or planted to interrupt or defuse this force and prevent it from reaching homes or fields.

A clump or row of trees and or fences and other structures may all serve as a windbreak. Depending on their size at establishment, trees and shrubs may take up to 20 years to grow into an effective windbreak but the benefits are usually worth the wait.

By diffusing the force of the wind, a windbreak may also reduce fuel costs for heating or cooling buildings, protect property from wind damage during storms, reduce soil erosion, keep snow from drifting against buildings, attract wildlife, and increase land value and beauty.

PLANNING WINDBREAKS

The following criteria are helpful in planning an effective windbreak:

1. The optimum foliage density for plants in a windbreak is about 60 percent on the windward side.

2. Windbreaks are most effective when they extend down to the ground.

3. The width of the planting is important. For most evergreen plants, two or three rows are sufficient but if deciduous plants are being used, four or five rows may be necessary. Rows should be staggered so that plants do not form straight lines.

4. Windbreaks work most efficiently when the length is 11.5 times greater than the mature width. For example, a windbreak that is 10 feet wide should be about 115 feet long.

5. The height of plants within the width of the windbreak should be varied to create rough windbreak edges. A mixture of tall, medium and short plants works better than all of one size.

DESIGN CRITERIA

Windbreaks obstruct and redirect the flow of wind. As wind strikes an obstruction it can move over, around and through it.

The extent of protection on the leeward (downwind) side is related to the height and length of the windbreak. An impenetrable (solid) windbreak creates a strong vacuum on the leeward side which reduces the protection provided. Windbreaks composed of living plants allow some of the wind to pass through which makes them more effective.

The zone of protection for a living windbreak is approximately twenty times its height. Maximum protection occurs in a range of 6 to 8 times the height of the planting so a windbreak 25 feet tall should be located 125 to 175 feet (no more than 300 feet) from the house.

Windbreaks should be at least three rows wide (5 rows is better) to be the most effective. The tallest growing trees (preferably evergreens) should be in the center rows, while the shorter trees and shrubs are best placed in the outer rows on both sides.

Rows of trees should be spaced about 10 to 20 feet apart, while each tree should be spaced between 8 and 18 feet apart within the row, depending on the size of the tree.

Windbreaks should be planted at right angles to the prevailing winds (usually westerly, therefore the wind-break should run north and south).

Woody ornamentals planted as windbreaks should include a mixture of deciduous and evergreen trees and shrubs. The following table documents the height and spacing required of a variety of species:

 

Species Hgt1  Between2  Within3
Austrian Pine Tall  16-20 14-18
White Pine  Tall  16-20  14-18
Scots Pine Medium 16-20 14-18
Red Pine Tall  16-20 14-18
White Spruce Medium 14-18  12-16
Douglas Fir Medium 14-18  12-16
Arborvitae Medium 10-12 8-12
White Cedar Medium 10-12 8-12
Lilac  Shrub  4-12 2-5
Viburnum Shrub 3-12  2-4
Honeysuckle  Shrub 3-12 2-4
Hgt1 = Tall: 50-60' Medium: 30-50' Short: 15-25' Shrubs: 6-10'
Between2 = Spacing in feet between the rows
Within3 = Spacing in feet within each row

SPECIES SELECTION

The above list of plant species includes those most commonly used in windbreaks. However, there are many other plants that will also work on your site.

A few of the plants on this list have excellent physical characteristics for use in windbreaks but have other problems that should be considered. Austrian and Scots (Scotch) pines are plants that tend to get disease and insect problems as they age. Young trees will provide a good windbreak but, after about twenty or more years, they are susceptible to needle cast diseases and may begin to decline. Mixing species of plants and staggering rows in the windbreak will allow for these problem trees to be removed later without leaving holes in the windbreak.

Most of these plants and many others suitable for windbreaks are available in garden centers, nurseries, mail order nurseries, and from soil conservation districts.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

 

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