When to Mow
Most cool-season grasses should be cut when they reach heights of 3 to 3-1/2 inches, typically once a week. Cut warm-season grasses when they reach 2 to 2-1/2 inches. Cut no more than 1/3 of the grass height at each mowing to avoid damaging the plants. If the lawn grows too high for you to cut off 1/3 the height and have an acceptable length, cut off one-third now and mow 1/3 off again in two or three days. Cutting more than 1/3 the height results in clumps of clippings that tend to lie on top of the lawn, decompose more slowly, and give the grass a less attractive, open, bristly appearance. In addition, short cutting will stunt or slow root grow and weaken the grass plants.