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Late fall lawn care and problems

gardening by Mary Robson, WSU Area Extension Agent
Darker, soggy days mean slower growth for lawns. But with the mild winters we often experience in the maritime Pacific Northwest, lawn care doesn't stop when flower borders go dormant and disappear.
   Keep fallen leaves and other tree debris raked off lawns. Turf grasses have to struggle enough against wet conditions without suffering from litter problems as well. Mow when the lawn needs it, not allowing the grass to get long and floppy. Mowing will be much less frequent than during summer conditions, but turf does continue to grow. Sharpen mower blades if they are dull. Using a sharp mower will help in keeping damper grass looking good.
   Late fall-early winter fertilization is crucial. Between about November 20 and December 10, apply a 3-1-2 ratio fertilizer. The percentage analysis is 3 parts nitrogen, 1 part phosphorus, and 2 parts potassium. This supplies plant nutrients needed to support the turf through winter. Maritime northwest lawns need 4-6 pounds of available nitrogen per 1000 square feet of turf per year, applied during four separate applications in November, April, June and September. Some fertilizers that fit this 3-1-2 ratio are 12-4-8 or 9-3-5 in analysis. Check the bags. To calculate application rates, recognize how the percentages translate. A 50-pound bag of 12-4-8 supplies 6 pounds of acutal nitrogen. The applicator would use 12 1/2 pounds of fertilizer per 1000 square feet for each of the four separate applications to get the required nitrogen level.
   A slow-release formulation is more appropriate in rainy weather. The idea is not to dump excess immediately-soluble nitrogen on the lawn, which could wash away into surface and ground water. A lawn that is over-fertilized (say, one that is treated with a 33-0-0, all nitrogen, and a heavy nitrogen source), will be less hardy to cold weather and more susceptible to disease problems.
   Phosphorous, for instance, isn't needed in big quantities, but contributes to turf health and should be consistently present. Washington State University specialists do not recommend using a feed-weed type product. That results in dumping herbicides uniformly on turf. Also, many of these broad-leaf weed killer products work best on weeds that are in active growth, which is not the case in fall and winter. Damp days are good days to hand-dig weeds from lawns!
   During low temperatures, when grass is frozen, avoid walking on it. Traffic over frozen turf reduces its quality. (In any case, the temptation to mow during icy spells is probably not overwhelming. Relax by the fire with the understanding that keeping off the grass does it a favor.)
   Mushrooms in the lawn can be a common winter occurence. In late October, many people discover clumps of mushrooms here and there in grass and under shrubs and trees. This fall, they are noticeable throughout lanscapes in western Washington.
   Mushrooms are the "fruiting bodies" of certain fungal organisms. Underground, the fungus produces a web of mycelia, which are whitish thread-like growths. Many of these are beneficial to soil and plant growth, contributing to root health and the proliferation of soil organisms. No control is needed. Knocking the mushrooms down or raking them away from the lawn, or simply mowing them, is adequate.
   Sometimes mushrooms will form a "fairy ring," a distinct circle of mushrooms surrounding an open space of grass. For people with a whimsical turn of mind, the circle does resemble a gathering spot for cavorting leprechauns. However, they can be disfiguring to the lawn. The underground web of mycelia can use nutrients needed by the grass, and sometimes the area within the circle will turn yellowish or brownish.
   Control, or management of fairy ring is primarily related to good turf care. It's more common on sandy soils and where turf is under-fertilized. Stay with an appropriate year-round turf maintenance schedule, and don't neglect the late fall fertilization. Keep the lawn in good health. Raking away the fairy ring mushrooms, aerating to disturb the underground parts are the major contributing helpful actions.
   In mid-spring, using a penetrating agent on the grass within the circle (to allow water to penetrate fully) can also help. Research suggests poking holes 6 inches deep at 6 inch intervals and soaking the area daily for a month with a detergent solution, at the rate of 2 tablespoons detergent to 3 gallons of water. Sometimes the soil within the circle will have become resistant to water penetration.
   There are no chemicals registered for treating mushrooms in home turf areas. The mycelia can go down into the soil as far as 8 to 12 inches, and total removal of the affected soil area is usually impractical.
   One fairly common fungal disease sometimes affects turf in the fall, winter, and early spring. Cool, moist conditions contribute to its proliferation. "Red Thread" is aptly named. As the disease begins, grass blades can look bleached or tan. The later stages of the disease produce light pink to reddish fungus strands growing from the tip of the leaves. The entire patch may show a reddish cast, or can be interspersed with unaffected blades, giving the area a "patchy" quality.
   Red thread can be reduced by maintaining adequate fertilization. It seldom kills grass, but is disfiguring. Again, apply 4-6 pounds of actual nitrogen per 1000 square feet per year in 4 different applications. The healthy lawn in active growth can usually outgrow red thread problems. If the disease progresses and continues, after all good cultural practices are tried, a fungicide can be applied. It may become necessary to do this in mid-winter when the grass isn't growing strongly. (Daconil, among others, is registered for use on red thread problems.) First, do good cultural care.
   Lawns don't ask for much in the winter, and as they green up again, they provide an attractive frame for landscapes!
   For more information about red thread, contact your county Cooperative Extension office and ask to buy Extension Bulletin 1016, Red Thread of Turfgrass. It costs $1.00 plus 32 cents postage. In King County, call 206-296-3900. In Pierce County, call 206-591-7170 between 9 and 3 on weekdays. In Snohomish County, call 206-338-2400.

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