Most northern lawns need about an inch of water a week, and most of this requirement is filled by the quick changing weather that we’re famous for.
Of course, one inch is only a guide. If you have real sandy soil that drains instantly, you’ll need more. Conversely, clay type soils might need a lot less frequent attention.
The summer brings the biggest problems. Hot sunny days evaporate water from the soil and grass quickly, and without replenishment, water in the soil drains down and away from the roots. Most grasses are able to go into a dormant state, where they shut down all above ground growth and even let their tops die back. By saving their remaining resources, once moisture is available again, the plants are able to resume growth.
Watering requirements are also influenced by the variety and condition of the grass. Good, healthy, mature grass has roots that go deep and can pull water from a greater volume of soil than shallow-rooted species. Young or unhealthy grass won’t be able to do this.
Some grass varieties have lower watering requirements than others. Generally, the Fescues are the most drought tolerant, followed by Kentucky Bluegrass and Perennial Ryegrass. Bentgrass has a very low drought tolerance and needs frequent (once or twice daily) watering. Of course, young grass plants of any variety haven’t had an opportunity to grow long roots or store up some resources will need frequent waterings also.
There are a couple of ways to tell if your lawn is parched. The simplest is to use a shovel to examine the soil a few inches down. If it’s dry, it needs water. It’s not always easy to tell when grass is wilting. Sometimes, when the plant’s internal water content drops too low, the plant cells begin to droop and shrivel. The grass plants lose their bright green color and turn a blue-green. Walking on wilted grass will leave footprints that don’t spring back.
Most grasses are able to recover from these initial stages of wilt, but it still puts a lot of stress on the plants and repeated wilting definitely isn’t good.