Proper mowing begins with choosing the correct height for your turf grass species. Cool-season grasses such as bluegrass, tall fescue, and perennial rye-grass are generally mowed at 3.0 to 4.0 inches high. The repeated mowing of cool season grasses too low places the turf under stress causing it to require more water. The resulting turf is thin and weak and is highly susceptible to weed invasion. Grass maintained at a taller height produces deeper roots reaching more available water.
To prevent weed germination, mow frequently at the tallest recommended mowing height. Weeds germinate rapidly when turf is scalped by mowing too short or when it is not mowed frequently enough. Both mistakes decrease turf density and cause an open canopy that favors weeds. Experts recommend a range of mowing heights to meet specific turf activities. Lower mowing heights require more frequent mowing. Annual grassy weeds — such as crabgrass — are especially a problem on turfs that lack density as the result of poor mowing.
Kentucky bluegrass lawns – mow 2.5 to 3.5 inches.
Tall fescue lawns – mow 3.0 to 4.0 inches.
Fescue/bluegrass lawns – 3.0 to 3.5 inches.
Bluegrass/ryegrass lawns – 2.5 to 3.5 inches.
Creeping red fescues – mow 3.0 to 3.5 inches.
Warm-season grasses, such as zoysia grass, should be mowed at 1-1/2 to 2-1/2 inches. In the spring (before green-up), warm-season lawns should be mowed at a low setting on your mower. This dead leaf and stem tissue should be removed from the lawn. Mowing at a low setting in spring increases the green-up rate, reduces thatch accumulation and allows for easier and more uniform mowing during the growing season. As the season progresses, mowing height should be adjusted upward so that by September you are mowing at 2 to 2-1/2 inches. Warm-season lawns should be left tall (2 to 2-1/2 inches) in the fall. Raising your mower height throughout the growing season will result in a thick, vigorous turf.
Set the height of your mower by placing it on a flat surface and measuring the distance from the ground to the bottom edge of the blade. Make height adjustments as needed.
The frequency of mowing will depend on the mowing height and growth rate of your selected grass species. The grass should be mowed when it has grown one-third taller than the desired height (this is called the one-third rule). Cool-season grasses in the spring and fall may require some weeks with two mowings (5 to 6 day interval). The same holds true for warm-season grasses throughout the summer months. Mowing more frequently is not as much extra work as you might think, because lawns mowed at the proper height cut more easily and quickly. Failing to follow the one-third rule results in the removal of excessive leaf tissue, stressing the grass at a time of the year when susceptibility to diseases runs high. This results in a thinned turf canopy with a poor root system.
Raise the mower deck if mowing has been delayed due to wet weather. Mowing heights can be slowly worked back down, over several mowings, to your desirable height.