University of Illinois Extension

Lawn Care for Summer

Man Mowing the LawnHow we manage the lawn during the summer greatly influences how well the lawn looks in the fall and even the next spring, said a University of Illinois Extension horticulture specialist.

"Lawns in northern Illinois are most likely a Kentucky Bluegrass blend," said Richard Hentschel. "Kentucky bluegrasses prefer the cool moist soils and air temperatures in the spring where the warmer season grasses will remain dormant in your yard until the soil is considerably warmer.

"While those warm season grasses thrive in the heat of the summer, our bluegrasses will generally go dormant if left alone only to return again once the heat of the summer turns to the cooler weather of fall."

Bluegrass lawns can be kept growing if you are committed to watering the lawn all summer, he noted. If you expect to water all summer, then a light summer application of lawn food will be needed to supply the lawn with the needed nutrients so that the lawn will continue to grow as you expect it to.

"If you are managing the lawn using organic materials or applying an inorganic fertilizer, the lawn food will be available as the grass plant needs it," he said. "If your community has watering restrictions, don't feel that because you can only water every other day that you should.

"When you do water, water deeply to encourage deeper roots, and that may mean watering in the morning and in the evening on the day you are allowed to, to put enough water on to soak in four to six inches. If the summer temperatures exceed mid 80's for several days, the lawn will temporarily shut down and wait for cooler temperatures before resuming growth and no amount of water will change that."

Besides the watering, cultural practices can make a big difference. You want the lawn to remain competitive against weeds all summer long by mowing the lawn higher, rather than shorter. Taller lawns will shade the soil, keeping weed seeds from germinating and becoming a problem by fall.

Sprinkler watering the lawn.Other benefits of a taller lawn mean a deeper, longer root system, that is better able to recover from stress or a disease outbreak. Deeper roots also mean that the grass plant is better able to obtain nutrients and the needed moisture from the soil in between any watering or rain that the lawn receives.

"To keep your lawn looking its best, be sure you keep the mower blade sharp," said Hentschel. "Sharpen the blade once a month if you can during the mowing season. If you start with a sharp blade, it does not take that much time to keep it sharp all summer."

If you allow the lawn to naturally go dormant, then you will not need any summer application of an inorganic lawn food. Any organic products used will still be available when growth resumes. Gardeners will need to apply enough water if we do not receive adequate rains to keep the crown of the grass plant alive so it is there to bring the lawn back in the fall when the weather moderates.

The lawn should receive between one quarter and one half inch of moisture a month. This is not enough to bring the lawn out of dormancy but is enough to keep the crowns alive. When lawns go dormant, the weeds keep growing and you should expect to see a few come fall. "Summer does provide a time to take an inventory of the lawn and decide what may need to be done as the lawn comes out of dormancy," he said. "There may be thin spots that need over-seeding, low spots that need topdressing so those areas do not stand water which can make those spots more disease prone."

The lawn may benefit from late summer core aeration, especially if you have soils that are compacted. Cores should be about three to four inches apart and that often can mean covering the lawn in two directions.

"The cores themselves can be allowed to dry and then allowed to filter back into the lawn to act as topdressing by either raking them in or breaking them up with the lawn mower the next time you mow," he said. "Core aeration and then topdressing with good organic matter will really benefit the grass plant long term, allowing it to perform at its best."