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Gardening: Fall lawn care

gardening by Mary Robson, WSU Area Extension Agent
Returning cooler weather signals time to review the lawn's condition. Does it have dead spots, weed problems, bare areas, shady nooks with moss, of all of these in one grim mix? September and October, while weather is still warm (or a bit warm), offer ideal times to work on the lawn.
   Start by giving the lawn good basic care. Keep leaves raked off, right through the length of the leaf-fall season. If leaves accumulate and then get wet, the lawn suffers damage from lack of sun and air. A light layer of leaves can be mowed over, and the combination of clippings and chopped leaves picked up and added to the compost. This breaks down into a superb soil conditioner after several months of composting.
   Lawns continue to grow throughout the fall and into winter if the temperatures stay mild, so mowing regularly is important. Don't allow the lawn to get long, rangy, and neglected.
   If you are using a mulching mower that chops and returns the clippings to the lawn, remember to mow often enough so that only about 1/3 of the blade is removed. This practice keeps the removed bits small enough for complete breakdown on the lawn.
   Watering and fertilizing will help with lawn improvements. Do not neglect the fall and winter fertilization: It's essential to get the lawn through winter in good condition. Apply fertilizer in September, and again between late November and early December. (Thanksgiving weekend is late this year and would be an ideal time to fertilize the lawn, to work off turkey sandwiches and football overload.)
   Use a fertilizer with slow-release nitrogen and a nutrient ratio of 3-1-2 NPK (N=3 parts nitrogen, P=1 part phosphorous, K=2 parts potassium). Many fertilizers specifically formulated for maritime Northwest lawn care correspond in general to these values, and may be found with listings such as 21-7-14, 15-5-10, or 12-4-8. Fertilizers containing slow-release components are particularly helpful for the winter application, because the nitrogen isn't washed into the ground and away from the roots rapidly by rains. Instead, it moves into the roots slowly and helps turf health throughout the winter.
   A suggested yearly schedule, researched by the turf specialists at Washington State University, is Dec. 1 to 15, Apr. 15, June 15, and Sept. 1 in western Washington. If you missed the September fertilization, do it now.
   WSU specialists do not recommend applying fertilizers containing a built-in herbicide (feed-weed type products). This common practice often leads to spreading the pesticide over areas that don't have weeds. Pesticides kill weeds only when they are growing actively, and this isn't the case with late-winter weeds. Also, many lawn herbicides containing the chemical "dicamba" must be used with care. It's been documented that this chemical, which kills broadleaf weeds, can damage trees and shrubs with roots running under the lawn area.
   Weed control is better done by spot-treating weeds with an herbicide now, in late September, while they are still growing. Or if using an herbicide doesn't appeal, dig them out. If the lawn is treated with fertilizer containing pesticides, do not use any of the resulting clippings immediately as a mulch. The weed-killer will damage plants it's applied under. Allow those clippings to compost for at least six months before using them. Used fresh, they are toxic to plants.
   Reseeding where weeds have been is important. Any area of bare ground will rapidly fill up again with weeds unless competing grasses are planted. Use a grass seed mixture adapted to the maritime Northwest. Make sure the lawn has good drainage, no standing water spots, and sun.
   Grass thrives on open, sunny prairies. It does not grow well in forest shade, but will thrive in semi-shade if the area is well drained and receives at least four or five hours of sun a day.

Visit WSU's Agriculture Site on the World-Wide Web at http://www.cahe.wsu.edu.