When
planning a windbreak it is helpful to determine its purpose. Windbreaks
are natural barriers that help reduce or redirect wind. They usually
consist of a combination of trees and shrubs. Windbreaks can be planted
to provide protection from the wind for people near a homesite, livestock
on rangeland or around a feed lot or protection for crops growing
in a field. Windbreaks also provide protection and habitat for wildlife.
A successful
windbreak planting depends on proper establishment and care during
the first few years after planting. Time spent in site preparation,
weed control, and replanting is repaid many times during the lifetime
of the windbreak. Take no shortcuts in the planning establishment
of your windbreak.
Some
of the factors to consider in planning tree plantings are:
Generally,
the primary tree-planting objective of rural landowners is protection
from the wind. A windbreak planting of trees and shrubs creates a
"wind shadow" on its leeward (downwind) side, providing that protection.
This protected area extends to a distance of 15 to 20 times the height
of the windbreak’s tallest trees; the most effective area extends
to about 10 times the height (10H) of the windbreak. For example,
if a windbreak is 30 feet tall, wind speed is reduced by 50 percent
300 feet downwind from the windbreak.
Because
wind eddies form around the ends of a windbreak, the planting should
extend 100 feet beyond the area to be protected. Any gaps or openings
in the windbreak funnel and accelerate the wind and reduce windbreak
effectiveness; planting different types of trees in the same row can
create gaps and reduce windbreak effectiveness. Avoid planting tall
growing trees under utility lines.
Windbreak
rows do not have to be placed in straight east-west or north-south
rows but generally should be perpendicular to prevailing winds.
Do not plant trees closer than 100 feet to roads, driveways, buildings,
or other areas being protected – snow drifts and blind corners created
in these areas can be hazardous. (Note: Snow can drift a distance
of approximately three times the height of the windbreak.)
Plant
at least three rows to achieve good wind protection – the greater
the windbreak’s density, the greater the reduction in wind velocity.
Shrubs or shorter trees can comprise outer rows, while evergreens
(the foundation of the windbreak) should make up at least one inside
row. Do not use the same species of plant in every windbreak row;
diversification of planting rows increases insect and disease resistance
and enhances wildlife habitat. Different tree types should not be
alternated or mixed within a row (to avoid plant overtopping
by faster growing species).
Before
planting, it is best to layout each row of the windbreak on the site.
This will allow the design to be customized for the positions of buildings,
roads or driveways, feedlots, field boundaries, utility lines, drainage
ditches, and other features at the site. Layout the dimensions of
the windbreak, including the spacing within and between the rows.
This process will help assure that your design will provide the protection
needed and will fit within the desired area.
Between-row
spacing varies with tree type and weed control methods. When cultivation
equipment is used (e.g. disks, rototillers, etc.), spacing should
be at least 4 feet wider than the equipment. A minimum spacing of
14 to 20 feet between rows will prevent stunting or overtopping.
