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Managing cool season lawns

By Rick Thomason

As we transition out of the spring and into summer, cool-season lawns in Johnson County need extra care. Cool-season lawns don’t like hot, humid weather. It becomes apparent when the days and nights start to heat up. Lawns can suffer if rain becomes scarce unless you have an irrigation system. This could be a possibility down the road.

Proper mowing is the best action you can take to help manage your lawn during the summer. Mow only when necessary instead of using a certain day of the week for your mowing day.Cool-season grasses slow their growth during hot summer days, so they may not need mowing every week unless we keep getting lots of rain.

Maintaining your mowing height between 3 to 3½ inches will help the lawn grasses recover much quicker and continue growing well during the hot summer days. Never cut off more than a third of the height of the lawn at one time. This means that you should time your mowing when the grass gets 4 to 5 inches tall and mow down to the height of 3 to 3½ inches. Regular mowing will help prevent the need for bagging the clippings. When the grass is cut regularly, clippings can be left on the lawn where they will decompose in a couple of days.

Never fertilize cool-season lawns in the summer. High levels of nitrogen can damage and kill these grasses during hot weather. Nitrogen in combination with hot temperatures encourages brown patches, a common fungal disease of cool-season grasses.

Try to avoid watering the lawn in the summer. The lawn can endure some dry weather, and sprinklers encourage the lawn to become dependent on frequent watering. If you start watering your lawn in the summer, you will need to keep doing this regularly or risk the loss of some of your lawn grasses dying. Frequent watering causes shallow root growth and makes the lawn grasses less drought tolerant.

By following these few simple practices in managing your lawn this summer, you should be able to enjoy a green and vibrant lawn this fall. Well maintained lawns and landscapes not only add to the aesthetics but also to the value of your home.

For more information on lawn maintenance, check out our UT Extension publication on “Fertilization and Management of Home Lawns” at