When a heat wave hits, even the best maintained lawns can suffer. Dry, hot weather can cause grass to turn weak and brittle, a state from which the lawn may or may not recover. Options for recovery range from watering and fertilizing to reseeding.
Heat damaged grass looks brown or pale yellow and is dry and brittle. It is easily damaged by foot traffic and mowing, which may leave it short and unable to grow. The lawn may show tire marks from mowers and brown and burnt streaks, especially if you mow during midday.
The amount of heat damage your lawn incurs is the result of several factors. As soil temperatures rise, root growth slows down and eventually stops, leaving grass with weak roots that prohibit growth. If you have not watered your lawn during the heat wave, it may have gone dormant. During dormancy, grass turns brown and although some grass types can survive dormancy, many are irreparably damaged. Lawns that are exposed to heavy sun, such as those with few trees or other sources of shade, are more likely to be damaged by heat waves. Likewise, lawns on south facing hills are especially vulnerable to heat. Lawn maintenance practices such as mowing in the heat of the day and keeping grass too short in spring and summer increased its susceptibility to heat damage.
If your lawn has small problem spots, you can watch and wait to see if the grass recovers. Although it may appear damaged, lawns go dormant if they do not have water but spring back to life when temperatures drop or rainfall occurs. If your lawn begins to green up and grow, continuing to water and fertilize as usual in fall should help it recover.
If there are burnt areas larger than the size of a handprint or your lawn does not seem to be improving, it likely needs to be overseeded. Wait until fall and use a drought-resistant seed such as tall fescue. Remove any dead grass, weeds and other debris with a rake so the seed will fall directly on the soil. Use a hose to thoroughly soak the soil before laying seed. Continue adding water until the soil is soaked to a depth of 6 to 8 inches. Before you lay seed, rake in a complete fertilizer at a rate of 1/2 pound of nitrogen per 1000 square feet. In areas less than 8 feet wide, seed by hand, evenly distributing grass seed. For larger areas, use a rotary or drop spreader to plant seed in rows, applying first in horizontal rows and then vertical until you have evenly covered the lawn. Overseed with tall fescue seed at a rate of 3 to 5 pounds per 1000 square feet.
To protect your lawn from heat and drought in the future, keep grass height between 2 1/2 and 3 inches and don't cut more than one-third of the grass height per mowing. Avoid mowing in hot weather when temperatures are above 90 degrees Fahrenheit. Keep foot traffic off your lawn and avoid applying herbicides and fertilizers during hot weather. If you can, water every three to four days in the early morning, applying at least 1/2 inch of water each time.
- Penn State College of Agricultural Sciences: Penn State Extension: Turning Up The Heat: Summer Turf
- Iowa State University Extension and Outreach: Drought Damaged Lawns Need Help
- University of Minnesota Extension: Lawn Renovation
- Michigan State University Extension: Turfgrass Establishment Following a Hot, Dry Summer
- Purdue University Extension: Purdue Agriculture News: Purdue Extension Has Advice for Repairing Drought-Damaged Lawns
- University of Kentucky: Kentucky Turfgrass Association Newsletter: Maintaining Kentucky Lawns During Summer Drought
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