Lawn Care for Hot Weather

Grass Type and Dormancy

• Cool-season grasses, such as fescue and bluegrass, naturally go dormant as soil temperatures raise above 70 degrees Fahrenheit. Warm-season grasses such as St. Augustine thrive in hot soils but go dormant when the soil cools down in fall. If you live in a climate with mild winters, a warm-season grass choice requires less maintenance to stay green during the heat of summer. In cooler regions, a cool-season grass provides a green lawn for a longer period but requires increased summer maintenance to remain green in the summer months.

Watering Schedule

• Most lawns need approximately 1 inch of water a week during cooler weather, but once temperatures rise above 85 degrees Fahrenheit, the grass needs 2 inches of water to replenish moisture lost through rapid evaporation. Watering deeply twice a week allows the moisture to penetrate to the entire root zone of the grass. Daily shallow watering only wets the soil surface and provides little moisture to grass roots. Irrigating in the morning allows the maximum amount of moisture to penetrate the soil so it's not lost to evaporation during the heat of the day.

Hot Weather Mowing

• Keeping your grass longer in summer helps keep the soil cooler and retain more moisture in the soil. The longer grass blades shade the soil surface, which slows down evaporation and moisture loss. Longer grass usually has longer root systems that are better able to access moisture reserves lying deep in the soil. Raising the mower blade height to between 2 ½ and 3 ½ inches provides the optimum grass blade length for summer lawns. If you allow the grass to go dormant, do not mow it until it becomes green again in cooler weather.

Special Considerations

• A healthy lawn survives hot weather and drought more readily than one already suffering stress. Treat lawns with herbicides in spring so weeds don't establish in the lawn. The weeds invade quickly as the lawn weakens in warmer weather. The thatch layer that sits on top the soil at the base of the grass plants can also create more stress to the grass if it's more than a 1/2-inch thick. Dethatching the lawn in the spring removes the excess thatch so that water can move into the soil more easily. Fertilizing also isn't necessary during summer heat. Instead, apply fertilizers in spring and fall, when the weather is cooler.