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Highs and Mows: The impact of proper lawn mowing height

Posted September 17, 2015
Updated February 26, 2016

Lawn mower

Ever go to get a haircut and before you can say “OH, NO. PLEASE, NO,” you stumble through the exit, triggering a cheap bell that twinkles in celebration of your shame, into the glaring sun with hair much shorter than you hoped to have? Likely, then, you and your lawn can commiserate.

Stop giving your lawn a buzz-cut, because that’s when weeds like crabgrass elbow their way in. So, if you’re tired of pulling weeds and want your lawn to be proud instead of looking for a cap to cower beneath, you need to mow at the proper height.

Mowing at the correct height for your grass is actually one of the easiest and most economical ways to combat weeds. This way, you’re using preventative maintenance instead of digging on your hands and knees or waving around a wand that has little to do with Harry Potter.

Many lawn enthusiasts mow their lawns shorter than recommended. That close-mowing may cause scalping (Not tickets; mowing so low that it exposes the stems of grass blades) and induce stress making the planted grass less able to compete with crabgrass and other weed species.

Another issue with the low-mow is that grass blades photosynthesize to provide food to the roots (not Jimmy Fallon’s house band). Chopping off the majority of the blade reduces the amount of energy the roots receive, making for a weak lawn that is more susceptible to stress, insects and disease. And, without the dense grass blades to block light, weed seeds are allowed to germinate and grow. In a scalped lawn, weeds can quickly dominate.

Lake Wheeler Turfgrass Field Lab in Raleigh used field experiments to determine the effect of mowing height of tall fescue. The experiment measured at 1 inch, 2 inches, 3 inches and 4 inches. Results of crabgrass incidence to those respective mowing heights were 95 percent, 48 percent, 13 percent, and 0 percent.

“The mowing height sweet spot for cool weather grasses is three and one half inches," according to Grady Miller, professor and extension turf specialist in the Crop Science Department at N.C. State. "For Zoysia and other warm season grasses, it is a bit lower at one and one half inches."

How do I know under which category my grass falls?

Cool-season grasses: Bluegrass, Bentgrass, Tall Fescue, Tall Fescue / Bluegrass mixes

Warm-season grasses: Bermuda grass, Centipede grass, St. Augustine grass, Zoysia grass

​This story was written for the North Carolina Sod Producers Association -- Great quality, great price, and a commitment to community.

This promotion is supported in part by the N.C. Department of Agriculture and Consumer Services Specialty Crop Block Grant Program.


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