How High to Mow Grass

Warm Season Grasses

• Warm-season grasses, those that green up in the spring and grow during summer, are generally mowed shorter than cool-season grasses. Popular warm-season grasses include Zoysiagrass and Bermudagrass. Since they grow close to the ground and prefer warm temperatures Zoysia and Bermudagrasses withstand and actually thrive better when mowed close to the ground. Cut them to a length of 1 to 2 inches. Any higher than 2 inches results in too much thatch, this slows growth and adversely affects the lawn's health.

Cool Season Grasses

• Mow cool-season grasses higher than warm-season grasses, especially during hot, summer months when these grasses are stressed. Among the most common cool-season grasses are bluegrass, tall fescue, ryegrass and buffalograss. Mow cool-season grasses to a height of 2 to 3 inches, although tall fescue should be mowed a little higher between 2-1/2 and 3 inches. Tall fescue and bluegrass are especially intolerant of short mowing and are weakened or damaged if cut shorter than 2 inches.

Exceptions

• During the summer months, cut cool-season grasses at 3 inches, their longest height, rather than at 2 inches. This helps retain moisture and protects the grass from the harsh sun and heat. In addition, do not mow overgrown grass down to the suggested height if doing so removes more than one-third of its length. Instead, gradually lower the mowing height in time until it is cut down to the desired height. This keeps the grass strong and healthy. Removing more than one-third of the height of grass in a single mowing causes the grass to be burned by the sun.

Frequency and Mowing Height

• Rather than mowing on a regular schedule, mow when the grass reaches a height that allows you to remove one-third of its length to achieve the desired height. For grass that is kept 1 inch tall, mowing should take place when it reaches 1-1/2 inches high. Similarly, grass kept at 2 inches tall should be mowed when it is 3 inches high, and grass kept at 3 inches tall should be mowed when it is 4-1/2 inches tall. This prevents sunburn, thinning, weeds in the lawn and other problems associated with removing too much of the grass blade in a single mowing.