   Windbreaks - July 2, 2003 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Creating a windbreak around your home or ranch will not only make the protected area more pleasant during windy periods, it will provide privacy, save on household energy consumption, and create favorable microclimate in the wind sheltered zone. The windbreak need not be created using live plant material. On small properties, a well-constructed fence may be a better choice. If you choose to use a living windbreak, then it is best to plan before you plant. Some important considerations include: water availability for irrigation, plant size and spacing, pests and diseases, wind direction, aesthetics, and plant species. Wind is a mass of air moving horizontally in response to changes in atmospheric pressure. As wind blows against a windbreak, air pressure builds up on the windward side (the side towards the wind), and large quantities of air move up and over the top or around the ends of the windbreak. Windbreak structure - height, density, species composition, length, orientation, and continuity - determines it's effectiveness in reducing wind speed and altering the microclimate. Windbreak height is the most important factor determining the downwind area protected by a windbreak. On the windward side of a windbreak, wind speed reductions are measurable upwind for a distance of 2 to 5 times the height of the windbreak. On the leeward side (the side away from the wind), wind speed reductions occur up to 30 times the height of the windbreak downwind of the barrier. The reduction in wind velocity behind a windbreak leads to a change in the microclimate within the protected zone. Temperature and humidity levels usually increase, decreasing evaporation and plant water loss. Soil temperatures in sheltered areas are usually slightly warmer than in unsheltered areas. Taking advantage of these changes in microclimate may allow earlier planting, greater fruit production, and growth of plants that would normally be marginal in your area. The prevailing wind direction in our area is from the southwest. This may vary depending on adjacent topography, vegetation, and structures. Once you have lived in the area for a while, you know where the prevailing winds blow. It is very helpful to create a scale drawing of your property that includes structures and existing vegetation beforehand. The decision to use living plants or build a fence is largely a function of space. You may think that cost is a consideration, but this is not always true. Plants may be just as costly in the long run and you will have to wait for them to grow before they effectively reduce winds. Green plants may be more attractive, but they require maintenance and do not create and effective barrier to animals like javelina, rabbits, and deer. Design and composition of a living windbreak depends on the space available and the species and size of trees. You should seriously consider planting several species of trees and shrubs in a windbreak. Fast growing trees such as willows can be removed once slower growing species reach adequate size. Plant species diversity is also a good strategy to minimize insect and disease problems. Remember that Arizona cypress and Leyland cypress often have bark beetle problems and Elderica pines have disease problems in Sedona. Other evergreen tree species to consider are Japanese black pine, live oak, or cork oak. Densely growing deciduous trees such as netleaf hackberry and Chinese pistache would also function reasonably well in a windbreak. Evergreen shrubs such as Photinia and Nandina could fill in gaps between trees. Use your imagination and create the perfect combination of living and constructed features for your unique situation. For technical information about designing windbreaks, visit the following University of Nebraska Extension web page: www.ianr.unl.edu/pubs/forestry/ec1763.htm. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at mgardener@verdeonline.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://ag.arizona.edu/yavapai/anr/hort/byg/. |