Even though the cool-season grasses, such as Kentucky bluegrass, predominantly grown in North Dakota, become dormant during hot, dry weather, they still require water to survive, contrary to some long-held beliefs, says Kasia Kinzer, North Dakota State University plant diagnostician.

""Not watering dormant grass during hot, dry periods, particularly on sodded lawns, can lead to dead grass and poor recovery,"" Kinzer says. ""The general recommendation is to provide turf about an inch of water per week, even during hot, dry weather.""

The actual amount of water may vary from this general guideline, depending on the number of trees or other plants competing for the moisture, thickness of the thatch layer, disease, clay content, level of compaction and other factors, so watering needs should be adjusted accordingly.

Watering in the morning is usually best because less water is lost to evaporation, compared with watering in the heat of the day. Also, the foliage is exposed to fewer hours of wetness (prolonged leaf wetness favors development of foliar diseases).

""If you do not have an automated sprinkler system and are typically rushed in the morning, then morning watering may not be practical,"" Kinzer says. ""I normally water during evening hours. This practice puts my lawn at risk for disease development, but I balance that risk by watering less frequently, about once per week during dry periods.""

For most lawns seeded to Kentucky bluegrass, applying about an inch of water during dry periods once a week is sufficient. If your lawn has a weak root system, which is the case for most sodded lawn samples Kinzer receives in the diagnostic lab, an application of one-half to an inch of water twice weekly is beneficial.

Sprinkler output can be measured by placing several small cups around the lawn and measuring the depth of water after a period of time. If the depth of water is greater than an inch, you probably are overwatering, especially if you have little thatch and few trees competing for the water. Overwatering promotes diseases and can literally drown certain plant species and some trees.

It is seldom necessary to run most sprinklers for more than 20 to 60 minutes. In the interest of conservation, it is a good idea to measure water output to avoid the expense (both financial and environmental) of overwatering.

For those who choose not to water during drought periods, be prepared for thinning or general decline, although some grasses may handle drought stress better than others.

""If you do notice decline as a result of not watering during dry periods, overseeding (broadcasting seed over the existing grass and raking the seed so it contacts the soil) can fill in thin areas,"" Kinzer says.

""Another key to a beautiful lawn is mowing height,"" says Ron Smith, NDSU Extension Service horticulturist. ""Lawns should be mowed two to three inches above the soil line. Grass cut to this height shades the soil and helps keep weeds from establishing. Shade also keeps the soil temperature cooler."

Mowing the grass shorter weakens it, making it more susceptible to injury from drought and disease. Short grass has a smaller and shallower root system and cannot get as much water during dry spells.

To adjust your mower to the right height, place it on a hard surface and measure from the blade to the hard surface. Cut your lawn often. Always mow at the same height and cut no more than 30 percent of the total plant height in one mowing. Letting the grass grow long in the fall does not benefit the lawn. It does make the lawn difficult to mow again and invites mice and other pests.

Grow grass longer in stress areas, such as shade and dry, sunny slopes. The greater mowing height will help the lawn to recover.

It is important to have a sharp mower blade. Dull blades fray the leaf tips, turning them brown. Dull mower blades also take more power or fuel to operate.

Allow grass clippings to return to the lawn. This will recycle nutrients and moisture, save on fertilization costs and cut down on labor required to complete the mowing task.

For more information on lawn care and related topics, go to http://www.ag.ndsu.edu/pubs/landscap.html.

NDSU Agriculture Communication