Sharpen mower blades for a clean-cut, healthier lawn

A sharp lawnmower blade pays off for the homeowner in the long run, says Dr. Aaron Patton, assistant professor/extension horticulture specialist for turfgrass with the University of Arkansas Division of Agriculture.

“A cleanly cut lawn helps increase turf health by improving recovery from mowing, decreasing water loss and increasing photosynthesis,” says Patton. “Aesthetically speaking, a clean cut lawn looks better.”

A dull mower blade causes leaf cut injury that heals slowly and causes greater water loss in the lawn.

Sharpen mower blades at least twice a year, or more often, for larger lawns, Patton recommends. Commercial users should sharpen mower blades at least every 40 hours.
Rotary mowers are greatly preferred by homeowners, although self-powered reel mowers are gaining popularity, says Patton.

“Rotary mowers work by cutting the grass blades in an impact, machete-type cut. This cut is less precise and often more damaging to the leaf blade than a reel mower cut,” he says. “The potential to scalp a lawn is higher when using a rotary mower, but the height of cut is easy to change and blades are easy to sharpen.”

Patton says blades on a reel mower (bedknife and reel system) should be sharpened by a professional.

To determine if your mower blade needs sharpening, kneel down and examine grass cuts. If a white fibrous tissue – the vascular system of the plant – is sticking out of the leaf blade ends, it’s a good indication that your mower blade needs sharpened.

“If you’re not comfortable with tools, hire a professional to sharpen your rotary blade,” says Patton. “For those do-it-yourself types, mowers blades can be sharpened fairly easily.”
Some shops specialize in sharpening equipment such as axes, mower blades, chainsaws, knives, etc.

“For the do-it-yourselfers, tool options include a file and vise or vise and angle grinder or bench grinder,” says Patton. Please wear appropriate safety equipment such as leather gloves and eye protection, when using any powered grinder, he advises

How do you decide when it’s time to invest in a new blade.

“When your blade becomes pitted or has been sharpened multiple times. My recommendation is for most homeowners to own two sets of blades,” he says. “Sharpen them both during the winter months and then replace one set half way through the summer.”

For more information about mowing your lawn and a comparison of reel and rotary mowers, see FSA6023 “Mowing Your Lawn” For more information about lawn mower safety, see FSA1005 “Lawn Mower Safety.”

For more information on how to sharpen a mower blade, do an online search for video instructions.

You can get a copy of the publications at your county extension office or go to the Cooperative Extension Service web site and select Publications, then Alphabetical List of All Publications.

The Cooperative Extension Service is part of the U of A Division of Agriculture.