Knowing when your lawn needs water and how much water it needs goes a long way toward keeping the lawn healthy and conserving natural resources. Proper lawn care, including techniques such as dethatching and aerating, helps your grass make the most of the water it receives and prevents waste.
Wait until the lawn shows signs of stress before watering. Grass that needs water has a bluish-gray cast, and the individual blades of grass wilt, roll or fold in response to low water stress. When you walk across a lawn late in the day, your steps leave footprints where the grass blades compact and low water levels prevent it from springing back up. Another method to determine whether the lawn needs to be watered is to use a screwdriver to dig a hole 3 inches deep. If the soil is moist at that depth, there is no need to water.
The typical lawn needs about 1 inch of water per week, and bluegrass lawns make do with 1/2 inch. Use this simple method to determine how much water your sprinkler system delivers: Place 5 to 10 straight-sided cans, such as coffee or tuna cans, in the path of the sprinkler. Let the water run for 15 minutes, and then dump all the water into one container. Measure the depth of the water in inches and divide it by the number of containers. The result tells you how much water your sprinkler delivers in 15 minutes. Multiply by 4 to get the rate per hour.
Excessive thatch causes the water to run off instead of sinking into the soil. Dethatch the lawn when it is more than 1/2 inch thick. Dethatch cool-season lawns such as bluegrass or fescue in early spring or late summer. Dethatch Bermuda grass lawns in late spring. Proper watering, mowing and fertilizing reduce thatch buildup.
The best time to water is early in the day when the lawn is normally covered with dew. When watering in the middle of the day, some of the water is lost to evaporation. Watering late in the day doesn’t allow the grass to dry before nightfall, which increases the chance of diseases.
Water doesn’t penetrate compacted clay soils easily. In small areas, loosen the soil with a spading fork. On large lawns, use a power tool to create small holes in the lawn. The holes allow water to sink into the soil and serve as water reservoirs that help reduce runoff. Aerate cool-season lawns in fall and warm-season lawns in summer.