I want you to take a test. Go out to your garage or shop and go to the nearest lawn mower. It doesn’t matter if its a reel or rotary. Look at the blade. Is the leading edge rounded? Are there any chips, dings, dents, gouges, splits, tears, or folded back edges? Is the bevel the correct angle? Check the manufacturer’s suggested angle. There are some variations among mower types and models. Is there even a bevel?

Okay, now go to your truck or tool box or storage area. Do you see an extra set of blades? If you answered, “no” please go on to the next paragraph. If you answered, “yes” please continue. Ask yourself the same questions in the first paragraph. Bonus question for rotary mowers… Do you have more then one set of extra blades for each lawn mower? A “yes” answer earns you the respect and admiration of all your fellow maintenance contractors, gardeners, and service shop owners.

How did you do?

If your lawn mower blades look like they’ve been mowing a rock garden and you don’t have any spares consider this - dull mower blades damage grass. Dull mower blades don’t “cut” grass, they tear it, rip it, or shred it. Torn grass is susceptible to the following problems: disease, insects, heat stress, use damage, herbicides, and chemical burn. Damaged grass requires more water for growth and survival.

Defined:Main Entry: lawn mower
Function: noun
Date: 1869
: a machine for cutting grass on lawns

Grass suffering from physical damage and abuse is weak because it is striving to repair itself or replace the injured blades. Its growth rate slows thus making it susceptible to further damage. The one major way grass resists damage from pedestrians, disease, insects, heat stress, and so on is its ability to grow fast and replace itself. Grass has enough problems without further aggravation from damage caused by dull mower blades.

A sharp mower blade cuts the grass evenly and cleanly. The next time you mow a lawn right after you’ve had the blades sharpened take a moment to observe the the cut ends of the grass. It won’t look like you took a pair of scissors and neatly cut each blade, but you will see a marked difference between the grass cut by a sharp blade and that cut by a dull one.

Ever notice a lawn a few days after it was mown and think that it looked “grey”? It was probably cut with dull mower blades. A greater portion of the top of the individual grass blades is left fuzzy. The fuzziness is caused by shredding. The shredded ends of the grass die and turn light green or yellowish thus giving the lawn a grey appearance.

Another factor to consider is that dull blades do not cut tall or wet grass as efficiently as sharp blades. With a dull blade there is more drag and friction with the grass. This slows the mower engine which in turn slows the blade resulting in even less grass that’s cut. The slower the blade cuts the slower you have to walk or ride. The end result is lost time, clogged chutes, “holidays” in the mowing pattern causing you to re-cut, and extra wear and tear on your engine.

Defined:Main Entry: sharp blade
Pronunciation: ’shärp ‘blAd
Function: adjective / noun
Etymology: Middle English, from Old English scearp; akin to Old High German scarf sharp and perhaps to Old English scrapian to scrape — more at SCRAPE
Middle English, from Old English blæd; akin to Old High German blat leaf, Latin folium, Greek phyllon, Old English blOwan to blossom — more at BLOW
Date: before 12th century
1 : adapted to cutting or piercing: as a : having a thin keen edge or fine point b : briskly or bitingly cold : NIPPING <a sharp wind>
1 a : LEAF 1a(1); especially : the leaf of an herb or a grass b : the flat expanded part of a leaf as distinguished from the petiole
2 a : something resembling the blade of a leaf: as a : the broad flattened part of an oar or paddle b : an arm of a screw propeller, electric fan, or steam turbine c : the broad flat or concave part of a machine (as a bulldozer or snowplow) that comes into contact with the material to be moved d : a broad flat body part; specifically : SCAPULA — used chiefly in naming cuts of meat e : the flat portion of the tongue immediately behind the tip; also : this portion together with the tip
3 a : the cutting part of an implement b (1) : SWORD (2) : SWORDSMAN (3) : a dashing lively man c : the runner of an ice skate


Some maintenance contractors change blades on their rotary mowers daily. This way they insure that the grass they mow is cut cleanly and efficiently.

Think of your lawn mower blade as the hull of a boat moving through water. Which hull moves faster and with less effort? The one that’s sleek and sharp or the one that shaped like the side of a barge?