Iowa’s windbreaks have lost functionality
Windbreaks are critical farm infrastructure, providing Iowa producers with crop yield increases, livestock protection and gains, reduced soil erosion, diversified income sources, energy savings, wildlife habitat, recreation, and aesthetics (Photo 1). As I travel the state, however, I frequently observe windbreaks with a complete loss of functionality. This large-scale loss is the result of many factors, including windbreak age, lack of proper maintenance, and impacts from extreme storm events and drought. At the core, these issues are exasperated by our historic reliance on a limited number of conifer species. Many windbreaks I’ve observed with near-zero functionality are comprised of a single, non-native, conifer species (e.g., blue spruce). We all know that native tree species perform best in Iowa’s variable climate. However, Iowa only has a handful of native conifers, and portions of Iowa have only one – eastern redcedar. In contrast, Iowa does have an extensive assemblage of native deciduous trees and shrubs – a large enough list to cover all of Iowa’s sites and geographic regions. To maximize windbreak functionality and longevity, it’s time we do away with our overwhelming reliance on conifers, and start considering deciduous trees and shrubs for Iowa windbreaks!
Photo 1: This multi-purpose windbreak acts as an asset to a rotational grazing operation in Polk County, Iowa. This windbreak was established using both coniferous and deciduous species, to acheive goals of livestock protection and income diversification from posts, fuelwood, sawtimber, and nut crops.
The year-round foliage and upright form of conifers make them nearly unbeatable for wind velocity reduction and privacy. Considering this, native (e.g., eastern redcedar) and non-native but hardy (e.g., Norway spruce) conifers should remain as significant components of our windbreaks. However, with diversity being the key to windbreak resiliency, functionality, and longevity, being open to deciduous trees and shrubs greatly increases our species selection options on a wide range of soils, sites, and geographic locations – areas where conifers have historically struggled. Wet, dry, clayey, sandy, and everything in between – there’s a list of native deciduous trees and shrubs that will work nicely on your site.
Deciduous trees can deliver on winter wind velocity reduction, it just takes more of them. In general, it would take approximately five rows of leaf-droppers to match the wind protection provided by a single row of conifers. For faster protection, you may plant stock at a tighter spacing. However, you must be diligent to thin at the appropriate time (when crowns begin to touch) to ensure long-term vigor. In addition, it may be valuable to consider trees that exhibit some degree of marcescence – also known as winter leaf retention (Photo 2). While not as dense as conifer foliage, the retained leaves do add winter wind reduction value, privacy, beautification, and wildlife benefits. Notably species that exhibit marcescence include oaks, ironwood, and witch hazel.
Incorporation of a diversity of native deciduous species also provides a multitude of compound benefits to Iowa’s farmers – notably, potential for income diversification and wildlife and pollinator habitat. In an example from Polk County (Photo 3), a rotational grazing operation used a solely-deciduous windbreak to protect a livestock winter feeding area. As added benefits, the producer plans to sustainably harvest sawtimber, fence posts, fuelwood, and nuts from this planting. Addition of shrubs on the windward and leeward side of windbreaks may aid in wind lift, as well as provide diverse structure (e.g., smaller, multi-stem) that may be utilized by a wide range of wildlife species. Selecting a range of shrubs (and trees for that matter) that bloom at different times will act to extend the availability of critical fuel for pollinators throughout the growing season. Not to mention delicious edible fruits for you!
Resources and Next Steps
Selecting the right deciduous tree and shrub species to match your site conditions AND achieve your windbreak functionality goals is an important decision. Your first stop should be your county USDA Service Center. From there, Natural Resources Conservation Service (NRCS) staff will work with you to design your windbreak, and select the appropriate species to achieve your goals. Private forestry consultants may also be able to assist in this matter. Check out the ISU Natural Resources Stewardship Contacts webpage to find professionals that serve your county.
For a chance to learn more on windbreaks, in an in-field setting, check out the Windbreak School (WBS) program – hosted by Iowa State University Extension, the Iowa Department of Natural Resources, and NRCS. Check the ISU Extension Forestry Upcoming Events webpage frequently for program dates and locations (note, WBS often occurs in late summer, to allow for ample time to plan and prepare for spring plantings). Lastly, check out our Windbreak School and Derecho Response for Woodlands and Windbreaks YouTube videos. So, let’s start moving away from our conifer reliance, and start appreciating deciduous species for the diverse benefits they may provide to Iowa’s farmers!
Photo 3: This solely-deciduous windbreak in Polk County serves to protect a winter cattle feeding area by reducing wind velocities and directing snow deposition away from the site. In addition, incorporation of valuable hardwood species (e.g., oak, walnut) may offer sustainable income potential. Note 5+ rows in design.