Trego's Mountain Ear

Windbreaks have been around for well over 500 years, and they are a pretty simple technology. A wind break reduces the wind speed over a certain area, protecting crops/structures/livestock from wind. Windbreaks can be designed to shelter areas from winter or summer winds.

Design matters. A well designed wind break will reduce wind speeds around areas that need protection. A badly designed windbreak can do the opposite. Badly placed gaps in windbreaks (and arguably there is no good place to put a gap in a wind break) can actually increase the wind speeds in a given area.

Windbreaks are typically several rows of plants, each row varying somewhat in height. The simplest (though far from the most effective) windbreak is a single row of trees. More layers increases density and the longevity of the windbreak.

Height and density are the most important features of a windbreak. The taller the windbreak, the greater the area it can protect. The denser, the greater the protection. A windbreak cannot have 100% density, the way a solid fence can. Trees can only grow so close together before growth is impaired. Still, even a low density (~35%) can cut wind speeds by half.

How much area can a windbreak protect? 2 to 5 times the height on the leeward side (reducing wind by varying amounts- less reduction the further from the windbreak). Windbreaks can have one or two legs and should not have gaps. In order to avoid increasing the amount of wind at the ends, the length should be at least ten times the height.

Because windbreaks reduce soil erosion and provide wildlife habitat, they are viable conservation projects for ordering from the state conservation nursery, which is a very cost effective way of acquiring trees/shrubs.

For more information on how to design an effective windbreak, check out this pdf from Montana State University Extension service. Need more information in order to select plants? This pdf from the USDA discusses various trees for conservation purposes in montana, including information about drought tolerance, leaf scorch and frost cracking. Helpfully, it will also include 20 year height and full height, which is an essential aspect of windbreak design.