This type of windbreak, usually one or two rows of trees with a shrub understory, is used for protecting cropland and orchards. Shelterbelts, on the other hand, are comprised of two or more rows of trees. They provide a greater reduction of windspeed than do windbreaks, but the protected zone is smaller. Because they are solid barriers, they create a zone of calm close to the trees, and a zone of turbulence further downwind. They are used to provide a high degree of shelter ina limited area, such as near barns, homes, livestock pens and equipment yards.
Hedgerows protect crops from damaging winds by blocking and slowing air movement.
Close to the leeward side of the hedge, however, air movement can be so slow that frost pockets form. Plants growing there may be damaged by a late spring frost. This can be avoided by thinning the hedge or pruning up the lower branches to allow cold air drainage. Conventional fencing can fill in large gaps as necessary. On relatively level ground windbreaks should be perpendicular to the damaging winds.