Lawn Mowing Height Chart: Cool- and Warm-Season Grasses

In short: Cool-season grasses such as tall fescue are kept tall, and warm-season grasses such as bermudagrass and zoysia are kept short. Three Extension services, writing for South Carolina, Illinois and New Mexico, give overlapping but different ranges, so the chart keeps each row with its source.

Why the chart has three answers for some grasses

Mowing height is set by the grass, and then adjusted for where it grows. The chart puts three university tables side by side rather than blending them: Clemson's Home & Garden Information Center, writing for South Carolina; the University of Illinois Extension; and New Mexico State University's residential-lawn column. Each row names its source, and each grass is spelled as that source spells it, so a "common bermudagrass" row from Clemson sits next to a plain "bermudagrass" row from Illinois.

Tall fescue shows how far apart they can sit. Clemson gives 2 to 3 inches in winter and 3 to 3.5 inches in summer. Illinois gives 2.5 to 3.5 inches year round, and New Mexico State 2 to 3.5 inches. Fine fescue disagrees most. Clemson's summer range is 2.5 to 3 inches, Illinois puts creeping red fescue at 1.5 to 2 inches, and New Mexico State lists fine fescues at 0.5 to 1.5 inches without saying why it is so much lower. If your lawn is fine fescue, follow your own state's guidance.

Cool-season and warm-season

The split in the second column explains most of the chart. Cool-season grasses grow fastest in spring and fall and slowly, if at all, in summer and winter, New Mexico State says, while warm-season grasses grow best in summer. The tall, bunch-forming cool-season grasses sit near the top of the chart; creeping warm-season grasses sit near the bottom, because the University of Tennessee notes that sod-forming grasses tolerate much lower mowing. Clemson's hybrid bermudagrass, at 0.5 to 1.5 inches, is mowed lower than common bermudagrass at 1 to 2 inches. St. Augustinegrass is the warm-season exception, kept at 2.5 to 4 inches in South Carolina.

The mower matters too. Clemson says most rotary mowers cannot give a quality cut below 1 inch on most grasses, or below 2 inches on zoysiagrass, and that bermudagrass and zoysiagrass are best cut with a reel mower.

Heat, cold and shade

Three of the four sources say to mow higher when the lawn is under stress. Clemson says to raise the cut for heat, drought or shade, and New Mexico State calls raising it in summer heat and winter cold a common practice. Tennessee keeps tall fescue at 2 to 3 inches in cool weather and suggests raising it to 2.5 to 3.5 inches before summer heat, and raising bermudagrass, centipedegrass, St. Augustinegrass and zoysia before the first autumn frost to help them through winter dormancy. Illinois takes the simpler line: for most lawns it suggests 2.5 to 3 inches, and says the easiest strategy is to set the height and leave it.

Worked example: a tall fescue lawn after a week away

A South Carolina tall fescue lawn is kept at 3.5 inches for summer, the top of Clemson's summer range and inside Tennessee's hot-weather range. New Mexico State's one-third table says a lawn kept at that height needs mowing when it reaches 5.25 inches, which takes off 1.75 inches.

Then a week away lets it reach 7 inches. Cutting straight back would remove 50 percent of the height in one pass, past the 40 percent New Mexico State says can scalp a lawn into tan and brown patches, and scalping during a stretch of stress can damage or kill the turf. Clemson's advice for a lawn that has got too tall is to raise the mowing height, then lower it gradually over the next few mowings until the recommended height is reached.

Related pages

If you are thinking about mowing less or replacing some turf, the HOA turf replacement letter covers lower-mowing lawns and other alternatives. Before winter, the sprinkler winterization checklist covers the irrigation system. A lawn that has thinned or browned for reasons other than mowing is a question for your county Extension office.