Water lawn deeply, but less frequently

  • Certain perennials, such as coneflowers, provide winter interest and seeds for birds, like this goldfinch.

    Certain perennials, such as coneflowers, provide winter interest and seeds for birds, like this goldfinch. Courtesy of Chicago Botanic Garden

By Tim Johnson
Chicago Botanic Garden
Posted7/24/2022 7:00 AM

Established bluegrass lawns need an inch of water each week to continue to actively grow and stay green throughout the summer. The recent heavy rains have been helpful to keep lawns green.

Water deeply once a week rather than lightly multiple times a week. This promotes a deeper root system so the grass will hold up better to stress. To determine how long it takes your sprinkler to deliver 1 inch of water, set out a coffee, tuna or other shallow can with straight sides and time how long it takes to fill it with an inch of water.


Be consistent with your watering practices -- either water on a regular basis all summer or let your grass go dormant during hot, dry periods. I do not water my lawn and it generally looks good unless there is an extended period of hot and dry weather in summer -- then it goes dormant, and I can mow less often.

If your soils are heavy and long periods of watering cause water to run off, you may need to split watering into a couple of times per week. Mowing your lawn at a height of 3 to 3½ inches also helps the grass to withstand stress, remain green and keep out weeds.

• Continue to groom your perennials and annuals by removing yellowing foliage and spent flowers. Make note of perennials that have flopped and need staking so that a support system can be installed next spring before the plants need it.

Gentle pruning back of more vigorous perennials can help keep your border from looking overgrown. Cutting leaves or stems off at the base can reduce the size of the plants without having them look pruned. You may want to let certain dried flowers on plants such as astilbe and coneflower remain standing for fall and winter interest. Goldfinches visit my coneflowers in fall and eat the seeds.

• You may find cicada killer wasps in garden areas with bare soil or sand (in a sandbox or below playground equipment, for example). They nest in my brick driveway at home. Cicada killers are solitary wasps. This wasp gets its common name from hunting cicadas to supply its young with a food source. The female digs a 6- to 10-inch-deep burrow that is ½-inch wide in the ground. Cicada killers are large -- about 2 inches long -- and black to red, with yellow banded markings on the abdomen. The head and transparent wings are reddish brown. A male cicada killer wasp may fly up to you to investigate as you enter his territory but is unable to sting. The females are capable of stinging but lack the instinct to guard their nest like honeybees, so it is best to leave them alone in your garden.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.

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