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posted: 7/23/2013 1:00 AM

Be consistent with watering

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  • To figure out how much sprinkling time equals 1 inch of water, set out a shallow can marked at the 1-inch mark.

    To figure out how much sprinkling time equals 1 inch of water, set out a shallow can marked at the 1-inch mark.

By Tim Johnson
Chicago Botanic Garden

Established bluegrass lawns need an inch of water a week to keep growing and stay green throughout the summer. This year, consistent rain and generally cooler temperatures kept lawns green and growing through June without much watering.

Be consistent with your watering practices: Either water on a regular basis all summer or let your grass go dormant during hot, dry periods.

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. If your soil is heavy and water begins to run off after long periods of watering, split the watering time into a couple of sessions a week.

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 1 inch deep.

Mowing your lawn at a height of 3 inches or more also will help the grass withstand stress and keep out weeds.

Shrubs that have put on a lot of growth this year likely need pruning. Prune them as needed to keep them in the proper scale for your garden. Their young twigs will be mostly hardened off in early July, so if you prune now there should be minimal new growth for the rest of the season.

Try using a pair of hand pruners instead of an electric hedge clipper to create a more natural look by making individual cuts at different heights throughout a shrub. For a more formal look, make cuts at the same height. Prune right above a leaf or set of leaves to help hide the cuts. Careful pruning will leave the plants smaller but not looking "sheared." Remove dead wood as necessary.

Some varieties of crab apple are very susceptible to a fungal disease called apple scab, and those not treated with fungicides in spring may be losing their leaves at this time. The remaining leaves will develop black and yellow spots.

Spraying with a fungicide at this point will not help, but you should give the affected tree extra care by providing supplemental water as needed and fertilizing in fall or next spring. Consider replacing disease-prone trees with resistant varieties.

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

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