When to Mow a Lawn for Grass Height

Grasses Mowing Heights

• With the exception of tall fescue, keep cool-season grass longer than warm-season varieties. Cool-season grass has finer blades than warm season and heavy mowing damages them. Keep warm-season grass types, such as Bermudagrass, at 1 to 2 inches; zoysiagrass at 1 to 3 inches; and buffalograss at 1-1/2 to 3 inches, according to Kansas State University. Keep cool-season varieties, such as Kentucky bluegrass and ryegrass at 2 to 3 inches and tall fescue grass at 2-1/2 to 3-1/2 inches.

Summer Mowing Heights

• Keeping cool season grass slightly higher in the summer prevents the grass from drying out from the heat. Grass mowed too short in the summer has shallow root systems, which can succumb to the heat or drought. Allowing the grass to grow slightly taller keeps the soil cool. Keep Kentucky bluegrass, perennial ryegrass, fine fescue and tall fescue 2-1/2 to 3 inches tall in the heat of the summer, as recommended by Ohio State University.

Fall Mowing Heights

• Mowing all grass types before winter prevents your lawn from contracting fungal diseases, such as snow mold. Letting grass grow tall in the late fall and winter snows causes grass matting. Underneath the matted grass, fungal spores germinate and spread. Mow your grass down to 3 inches in height. Wait for the grass to grow to 4-1/2 inches and mow it down to 3 inches, suggests Cornell University.

Other Factors

• Mow your lawn when it's dry. Mowing wet lawns causes grass clippings to clump on the lawn. Clumped grass clippings reduce the amount of sunlight and air reaching the turf grass. However, grass clippings are beneficial for lawns, as they contribute nitrogen to the soil. Distributing a fine layer of grass clippings over your yard reduces the need for a large amount of nitrogen fertilizers. Mow grass right before applying either pre-emergent herbicides or pesticides, so that the chemicals sink into the soil.