A thick, dark green lawn is a beautiful sight in spring. Kentucky bluegrass and other cool-season turfgrasses thrive in the cool temperatures and frequent rains of spring. However, growing conditions for cool-season turfgrasses are usually more difficult during the summer months. Hot, dry weather may cause the grass to turn brown and go dormant.
Gardeners have two basic options when confronted with hot, dry weather. One option is to do nothing and allow the grass to go dormant. The alternative is to water the turfgrass during dry weather to maintain a green, actively growing lawn.
Gardeners can enjoy an attractive, green lawn and conserve water by following proper irrigation practices.
When to Water
The appearance of the turfgrass is the best way to determine when to water the lawn. The ideal time to water a lawn is at the first signs of water stress. Turfgrasses receiving adequate supplies of water are normally dark green in color. One of the first signs of water stress for cool-season grasses, such as bluegrass, is a bluish green color. Footprints that remain in the turf after walking across an area are another sign of water stress.
Frequency and Amount of Water to Apply
Most lawns in Iowa require approximately 1 to 1 1/2 inches of water per week. When watering the lawn, apply this amount in a single application or possibly 2 applications 3 or 4 days apart. Avoid frequent, light applications of water, which promote shallow rooting and lush growth. Lush, shallow-rooted turfgrass is less drought tolerant. It is also more susceptible to pest problems. To determine the amount of water applied by a sprinkler, place 2 or 3 rain gauges within the spray pattern.
Time of Day to Water
Early morning (5 a.m. to 9 a.m.) is the best time to water a lawn. A morning application allows the water to soak deeply into the soil with little water lost to evaporation. When watering is completed, the turfgrass foliage dries quickly. Watering at mid-day is less efficient because of rapid evaporation and strong winds may cause uneven water distribution. Strong, mid-day winds may also carry water onto driveways, sidewalks, or streets, wasting considerable amounts of water. Watering lawns in late afternoon or evening may increase disease problems.
Dormancy is a natural survival mechanism for Kentucky bluegrass and other cool-season grasses. During extended dry periods, turfgrass foliage will cease growth and turn brown. While the foliage is dead, the turfgrass crowns and roots remain alive. Generally, turfgrass can remain dormant for 4 to 6 weeks without suffering significant damage. However, lawns are at risk of dying if dormant for longer periods. Apply 1 to 1 1/2 inches of water in a single application to lawns that have been dormant for 4 to 6 weeks. Water again 7 days later. The grass should begin to green up after the second application of water.
Newly Seeded Lawn
After seeding, keep the upper 1 inch of soil moist with frequent, light applications of water. It's often necessary to water newly seeded areas once or twice a day. With adequate moisture and proper soil temperatures (55°F or above), most turfgrasses should germinate in 2 or 3 weeks. Grass seedlings are very susceptible to desiccation injury. Continue to water the grass seedlings once or twice a day. When the turfgrass reaches a height of 1 to 2 inches, gradually reduce the frequency of watering, but water more deeply. A thorough watering once a week should be adequate after the new turf has been mowed 2 or 3 times.
Newly Laid Sod
A newly sodded lawn should be watered once or twice a day for the first 7 to 10 days. Apply enough water to moisten the sod and upper 1 inch of soil. Sod should root to the soil in about 10 days. At this point, gradually reduce the frequency of watering, but water more deeply. After the sod has been mowed 3 or 4 times, a deep watering once a week should be adequate.
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