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.

Tips to make your mowing job more productive

At first glance, mowing a lawn doesn't look like a difficult job requiring much thought. We're just cutting grass - right?

"But lawn mowing done properly goes several steps farther than just firing up a lawn mower and cutting grass," says Gerald Alexander, Hempstead county extension agent with the University of Arkansas Division of Agriculture.

Mowing is a destructive practice to the plant because it removes a portion of leaf tissue that could be used to provide energy for the plant, he says. When leaf tissue is lost, the plant responds by redirecting energy from storage in the roots to producing more leaf tissue. If a lawn is cut too low, the plant has a more difficult time recovering because it lacks adequate leaf area to help it use soil nutrients efficiently.

Whenever mowing is necessary, never remove more than one-third of the leaf blade in a single mowing. For example, if you want your turfgrass to maintain a height of 3 inches, mow when the turfgrass stands 4.5 inches tall. This will normally translate into a once-weekly mowing pattern under ideal growing conditions, according to Alexander.

Mowing high is preferable to mowing low because overall plant health increases and weed competition decreases. The type of turfgrass in your lawn will determine how high your lawn should be mown.

The suggested mowing heights for common lawngrasses are: Centipede – 1.5 to 2 inches; St. Augustine grass – 2.5 to 4 inches; Zoysia grass – three-quarters of an inch to 2.5 inches; common Bermuda – 1.5 to 2.5 inches.

Alexander says he frequently hears questions concerning grass clippings left on the lawn.

It used to be thought that grass clippings contributed to thatch buildup. However, research has shown that grass clippings don't contribute to thatch buildup. Clippings are actually good for the soil because they return nutrients to the soil when they decompose.

"As long as you don't allow your lawngrass to become excessively high between mowings, you don't need to bag them. Clippings are often bagged because people fear the spread of lawn diseases through the return of lawn clippings. The spores that cause lawn disease are present whether clippings are returned or bagged," says Alexander.

Lawns are best mown when the turf is dry. The clippings are more evenly distributed on a dry lawn than a wet lawn. Wet mowing wet causes the clippings to clump and clog the mower. These clumps will then need to be picked up to prevent smothering the turfgrass beneath. Wet mowing also opens the door for disease organisms to enter the plant. Slipping and tearing turfgrasses are other reasons not to mow under wet conditions.

When lawn mowers are operating, he says, always pay close attention to safety. A mower blade can pick up an object from the ground and throw it with a velocity strong enough to damage cars, houses and inflict serious harm to humans and animals.

Additional information on lawn mowing can be found in the publications section of our web site, or at your county extension service office. The Cooperative Extension Service is part of the U of A Division of Agriculture.