Kentucky bluegrasses, fescue and other cool-season grasses naturally protect themselves by going into a semi-dormant stage during periods of high temperature or drought. They cease growth and turn brown, but bounce back quickly with sufficient water and cooler temperatures, as long as they have not been severely thinned by excessive summer traffic.

Except in cases of extreme prolonged drought, tall fescue and Kentucky bluegrass do not need water to stay alive during the summer. However, their appearance suffers. During dormancy, drought-tolerant weeds such as plantain, thistles and dandelion dominate lawns.

Because of its deep, extensive root system, tall fescue remains green longer into the summer than other non-irrigated cool-season grasses.

Kentucky bluegrass has many underground stems, called rhizomes. Each rhizome can produce several new bluegrass shoots that result in turf thickening in autumn when water becomes available following summer dormancy.

The principal purpose of summer watering is to maintain an attractive green surface. Watering will not substitute for poor fertility or improper mowing, and can encourage crabgrass and other weeds. Extra growth stimulated by watering increases fertility requirements, thatch accumulation and disease pressure.

If you cannot give attention to management, let the turf follow its natural tendencies to go dormant during summer. (Plants are brown in appearance from lack of water, but not necessarily dead.) Homeowners who have a lawn care service should not allow their lawn to enter drought dormancy.

Rules for watering
Shallow, frequent sprinkling to add a little water each day is not generally recommended. It encourages shallow, weak roots, crabgrass and some diseases.

Irrigate to the full depth of the root system often enough to prevent wilting.

Kentucky bluegrass and fine leaf fescue roots may not reach depths greater than 4 to 6 inches during the summer. About 1 inch of water (620 gallons per 1,000 sq ft) can be stored in an average soil to this depth, and this should last about a week.

A reasonable guideline for summer lawn irrigation is to apply enough water in addition to natural rainfall to total 1 inch per week. Greater frequency with lesser amounts may be required on sandy soils that cannot store this much.

Don't guess at how much water is being applied to reach the desired wetting depth. Place tall, straight-sided cans in the sprinkler pattern. Measure water depth in the cans to determine the amount of water applied.

Thrust a small probe (screwdriver) into the soil. Decreased resistance to the probe in wetted soil can help gauge depth of wetting.

Some sprinklers apply water faster than soil can absorb it. Few established lawn soils in Missouri can absorb 1/2 inch per hour; many absorb much less. To prevent waste, move portable sprinklers frequently. Properly engineered permanent irrigation systems with timing controls for "interval watering" do the best job. A soaker hose is also an excellent choice.

Steep slopes, hard spots and hot areas require special attention. Mechanical aeration, extra slow watering and use of wetting agents may help water infiltration.