Raise the Mowing Height for Weed and Grub Defense
DOWNLOADDecember 21, 2023 - David Smitley, Michigan State University Department of Entomology
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EmailMichigan has a tradition of mowing lawns short. Perhaps it is because many people want their lawn to look like a golf course fairway. Unfortunately, this is not practical for the average homeowner because golf course fairways are mowed three times per week with a frequently-sharpened reel mower, and irrigated daily during the summer. Trying to mow your lawn at a height less than 3 inches is actually stressful to your lawn and may result in the need to apply more insecticide and herbicide.
What height do you mow at?
It’s easy to determine the true cutting height of your mower. Pull your mower onto your driveway or sidewalk and measure the distance from the cement surface to the bottom of the blade-protection covering that goes all the way around the path of the blades. Most lawn mowers have an adjustment that allows the mowing height to be set between 2 and 4 inches.
What mowing height is best for my lawn?
The highest setting on your mower! The top setting for most mowers gives a cutting height between 3.25 and 4 inches. This is best for your lawn, but at a setting of 4 inches you may sometimes see some “laying-over” of turf blades that some people find undesirable. For this reason, some people prefer to mow at 3 or 3.5 inches. For the healthiest and most sustainable approach, 3.5 to 4 inches is most desirable.
Why is mowing high good for my lawn?
Raising your mower height provides five valuable services:
- It makes scalping (turf damage from mowing too short) much less likely to happen.
- It allows you to clip about 30 percent of the leaf blade each time you mow (the optimum proportion).
- It promotes establishment of a larger root system, which is more drought tolerant.
- It provides broadleaf weed and crabgrass control by shading the soil surface.
- It establishes a grub-tolerant lawn because of the larger root mass.
The weed and grub control provided by raising your mowing height means you can use less pesticide on your lawn. In fact, if you combine raising the mowing height with modest applications of fertilizer (1 to 4 lbs. N per 1,000 sq. ft. per year, depending on how green you want your lawn), and watering during dry periods, you may not need to use any pesticides – herbicide for weeds or insecticide for grubs – on your lawn. If you have not been mowing your lawn at the recommended height of 3-4 inches and watering during dry periods, you may need to do this for at least one year to establish a healthy lawn and transition away from using pesticides.
For more information on a wide variety of Smart Gardening topics, visit www.migarden.msu.edu or call MSU’s Lawn and Garden hotline at 1-888-678-3464.
This work is supported by the Crop Protection and Pest Management Program [grant no 2021-70006-35450] from the USDA National Institute of Food and Agriculture.
