ISSUE 6 June 8, 2000
WARMER WEATHER ARRIVING, MOW HIGH; MUSHROOM PROBLEMS
With the arrival of warmer weather, temperatures going into the mid to upper 80's or more, our cool season grasses come under stress. To help alleviate the high summer temperature stresses, set the mower high, up to the max of 3 inches. At this height, the turfgrass blades will be able to carry on the important photo synthetic activities at optimal levels. This will also encourage deeper root development and fewer weeds invading the turfgrass.
While mowing has benefits for turfgrass development and quality, it is also a stressor on the grass plants. Be sure the blade is sharp, that the mowing direction is altered each time to spread out the compaction, and if possible, mow going into the evening hours when the temperatures are lower. Mowing generally enhances disease development. When wounded from mowing, the cut tips offer avenues of entrance for many pathogenic fungi, such as Rhizoctonia and Fusarium. In summer heat and humidity when the dew point temperatures are high, Pythium, a fungal disease, frequently shows up on well-fertilized lawns with poor surface drainage. Many times the spores are picked up and spread when mowing.
Not mowing the turfgrass is a poor alternative. Mowing definitely causes the grass to thicken up by tillering, it helps keep it in a vigorous vegetative growth cycle, helping the grass plant make a "sod" which we all want. Frequency of mowing is as important as height of mowing. Frequent mowing removes shorter leaves of the grass plant, allowing it to fall deeper into the turf canopy, and thus decompose faster.
"Mow sharp, high, frequently, and let it fall".
Several calls have come in concerning mushrooms showing up in lawns. They are the result of high moisture content in the soil interacting with decaying organic matter; old roots, construction debris, excessive thatch, etc. The question also comes up: "are they edible?" I dont know, and when I dont know, I would rather consider them to be poisonous. Thats how I have lived as long as I have!
If you are a golfer, get out and practice your swing on the mushroom heads. There are no chemical controls, and they will disappear in a few days as the warmer, drier weather settles in.
NSDU Extension Horticulturist and Turfgrass Specialist
Department of Plant Sciences