Windbreak

Windbreaks have been used extensively in Iowa since the 1930’s. Reducing wind speeds during the year, controlling snow drifts, enhancing property value, reducing energy costs, and providing a habitat for wildlife are the many benefits of planting a windbreak. While their popularity fluctuated from the 1930’s to the 1970’s, you will still see them functioning for farmstead protection today.

Windbreaks should be designed properly in order to serve their maximum potential. In Iowa, protection from the cold north and winter winds is needed; therefore, windbreaks should be sited to mitigate these winds. Research suggests that a minimum of three rows is need to provide the adequate protection of wind forces that can reach eight times its height. The outermost row should consist of different types of deciduous shrubs, reducing the mass of snow at ground level, and thus protecting the adjacent conifers. Conifers, of multiple species, may be placed as the main tree line in the windbreak. Several species of spruce, pine, and arborvitae maintain the density of the Iowa Arboretum north windbreak. Using a wide selection of plant species not only reduces the likelihood that a disease or pest will completely decimate a windbreak, but will also minimize the competition caused by different growth rates.

Large deciduous trees can also make up a windbreak where wind protection isn’t as imperative due to the contour of the land. Such windbreaks only account for 5-20% reduction of wind in comparison to conifers. For optimum wind lift of a deciduous planting, plant the tallest trees inside and the shortest shrubs on the upwind (north and west) side of the windbreak. Incorporating a double row of shrubs on the outside of the windbreak provides further reduction of snow accumulation.

The Iowa Arboretum’s windbreak was established in 1982 as a collection, but added on as a two-part collection with deciduous and coniferous windbreak designations several years later. Unfortunately, the north side windbreak suffered extensive damage in the August 2020 derecho; the bulk of the trees needed to be removed and new trees planted. The windbreak on the west side, a row of Quercus bicolor, swamp white oak, remained virtually untouched.