   The Finer Points of Mowing Turf - August 14, 2002 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Many lawn owners are confused or misinformed about proper care of turf. One common misconception is: mow your lawn as short as possible to avoid frequent mowing. In reality, a short mowing height actually stimulates turf growth while also triggering a stress response in the grass. This stress has a negative effect on the grass, which increases water consumption, increases nitrogen demand, and reduces lawn density allowing weeds to more easily establish. The number one rule of lawn mowing for all species and varieties is: never remove more than one third of the height of the grass at one mowing. If more needs to be removed, do it gradually over the next couple of mowings. The longer the blade length, the more leaf area the plant has. Greater leaf area allows it to produce more photosynthate (sugar) and store more energy in the roots. This stored energy is a reserve that allows the grass to survive stressful periods. During summer, warm season grasses are actively growing and benefit from frequent (more than once per week) mowing. Correct mowing height is determined by the species and variety of grass being grown. Common bermudagrass should be mowed at 1 to 2 inches. Hybrid bermudagrass should be mowed at 1/2 to 1 1/2 inches. Zoysiagrass should be mowed at 1/2 to 1 1/2 inches. Buffalograss should be mowed at 2 to 3 inches. Cool season grass species are resting during the summer. They grow, but very slowly. Mowing height is critical, but more importantly, you should never fertilize a cool season grass in the summer. Tall fescue and Kentucky bluegrass should be mowed at 2 to 3 inches and ryegrass should be mowed at 1 to 2 inches. The number two rule of lawn mowing is: keep the lawn mower blade sharp. Dull lawn mower blades whip the grass rather than slicing it cleanly. Most homeowners have rotary lawn mowers. These have a single blade that rotates at high rpm on a plane parallel to the lawn surface. The other style of mower is the reel mower. Reel mowers are designed for close mowing (less than 1 1/4 inches). These have several blades arranged in a circular, twisted pattern that snips the grass against a fixed blade called the bed knife. Contrary to popular belief, leaving the grass clippings on the soil surface contributes very little to thatch build-up when proper mowing is practiced. With proper mowing height and frequency, clippings will decompose rapidly. However, excess clippings left on the lawn will weaken the turf. If long blades are sitting on top of the grass, then they should be removed. Mulching mowers chop the clippings in finer pieces and increase the decomposition rate. At any rate, allowing clippings to stay on the lawn will decrease fertilizer needs by up to 25%. Some final lawn mowing tips follow. Avoid mowing wet grass, but during rainy weather it is better to mow the grass wet than let it get too tall (as if this is a problem in Arizona). If it does get too tall, cut only one third of the total height at any one cutting. You may even need to only cut a one-half to three quarter swath rather than full width. When leaving the clippings on the lawn with a side discharge mower, mow in the direction that puts clippings onto the area that has already been mowed rather than concentrating the clippings in the center of the lawn. Also, turf will benefit from mowing in different directions each time the grass is cut. 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 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/. |