Problem: Drought-caused Dormancy
Cool-season grasses react to drought by becoming dormant. Grass blades die, but the crown, roots, and rhizomes remain alive. Buds in the crown begin growing when it rains. Greening is usually visible 3 days after a rain or irrigation. Kentucky bluegrass can withstand several weeks of drought this way. Other cool-season grasses survive for lesser times. Healthy, drought-hardened lawns survive longer peiods of dormancy than do weakened ones, or lawns adapted to frequent watering. Drought-dormant grass blades are dead, but rhizomes, roots and crown are visibly alive. Look for tiny green buds on the crown, and plump, white rhizomes. Dead rhizomes are brown and withered. Common Kentucky bluegrass survives drought best. Perennial ryegrass and some of the newer, more refined bluegrass varieties withstand drought less well. Fine fescue does not enter dormancy, but survives drought well in the shade. Fescue in the sun will not survive for long.
Dormant lawns do not require mowing or other care. If the dry period is extended, apply about 1/2 inch of water every 2 weeks to help the crown survive the drought without bringing it out of dormancy. To condition plants for drought periods, mow the grass high (at least 2 inches) before the dry period, feed lightly with a fertilizer high in potassium, and withdraw water slowly by watering less frequently. This regimen toughens the plant by encouraging deep roots.