6 Signs You Need to Sharpen Your Lawn Mower Blade for Healthier, Tidier Grass

Lawn mowers are used a lot during spring and summer when grass seems like it grows overnight. To keep up with the frequency of use, your lawn mower needs to be serviced throughout the two seasons. Along with regular cleaning, an oil change, and checking the air filter and spark plugs, you will want to ensure that your lawn mower blade is sharp to keep your lawn tidy. 

Beyond aesthetics, a sharp mower blade is vital for your lawn's health. A dull blade could lead to patchy, uneven, and yellow grass. It might create ragged edges that make your lawn susceptible to pests, weeds, moisture loss, and disease. Essentially, a dull mower blade compromises the health and appearance of your grass. So, how do you know when to sharpen your mower blade?

We spoke to lawn care experts who shared the most common signs your lawn mower blade needs sharpening so your grass can flourish all season long.

Uneven Cut or Scalping

A sharp mower blade is the key to achieving a clean, even cut. Any result other than that could be a sign that you need to sharpen your mower blade. "If your lawn looks patchy or uneven, even after mowing on a consistent height setting, your blade may be dull or damaged," warns Matthew Koch, a lawn expert at Scotts Miracle-Gro. Scalping your lawn so areas of exposed soil are showing is another sign your lawn mower blade needs sharpening. 

Torn or Frayed Grass Tips

Dull mower blades can tear or rip the grass tips, giving your lawn a dried-out and yellowish appearance, says Eric Halfman, lawn equipment go-to-market manager at John Deere. He adds that this kind of tearing can provide an entryway for disease. "A properly sharpened mower blade will create a lift effect which produces a better cut and minimizes lawn damage," explains Halfman.  

Running Out of Fuel Faster

If you notice your fuel level dipping faster than normal, it may be a sign that your lawn mower blade needs sharpening. "Dull blades make the engine work harder than it needs to, using up to 20 percent more fuel," says gardening and lawn expert Chris Ramos. To avoid this, he recommends sharpening your lawn mower blade once a month to preserve your lawn and save energy. 

Increased Mowing Effort

Anyone who has mowed a lawn knows that it takes a good bit of exertion. But if you have to push harder or longer than usual, it could be a sign that your blade needs sharpening. "If your mower is working harder, slowing down, bogging, or requiring multiple passes to get a clean cut, it’s likely the blade is too dull to cut efficiently," says Koch. A seasoned mower should be able to gauge the level of effort needed to mow a lawn with a properly sharpened blade and recognize when something is awry.

Gray or Dull Grass Appearance

Inspect your lawn for a change in color after each mow. It should be a vibrant green during the summer, not yellow, brown, or dull. A change in the color of your grass after mowing could be a sign it's time to sharpen the blade. The color differences can be stark or subtle, but the cause is usually the same–your mower blade needs attention. "A lawn mowed with a dull blade often takes on a hazy or muted tone, especially in the sunlight," says Koch.

A Visibly Bent, Rusted, or Nicked Blade

Check for any visible nicks, bends, or rust when inspecting your lawn mower blade throughout the summer. These imperfections might be indications that you need to sharpen your mower blade. "Physical damage or corrosion affects cutting performance and should be addressed immediately," advises Koch.