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For years, I defaulted to sharpening my lawn mower blades once–when I took my mower out at the beginning of the summer season. But the truth is that is not nearly often enough. At the least, it’s worth checking your blade sharpness every time you start your mower.

Many landscapers sharpen their lawn mower blades once a week. Their rule of thumb is one sharpening for every 25 hours of mowing time. With travel time, that usually works out to once a week.

So if you use your mower one hour per week for just half the year that equals 25 hours, right? Therefore, you can just sharpen them once a year, right? Not so fast!

The Home Depot estimates that no matter how little you mow, you want to sharpen your lawn mower blades at least twice a season. The chain store’s blog recommends one sharpening first thing in the spring and another mid-season. This is because your blades will rust and dull over time, whether or not they are used.

One benefit of a mid-season sharpening is that your blades will be sharp again for the late summer months. In the late summer, grass grows slower and recovers from mowing slower. Sharper blades mean the grass has an easier time recovering. But more on that later.

Gloved hands sharpening a mower blade on a bright orange grinder machine.
Sharpening mower blade | Oxana Medvedeva via iStockPhoto

If you have a huge lawn and mow for five hours a week, the absolute minimum you’ll want to go before sharpenings is five weeks. That said, there are other ways that your blades may dull besides time mowing.

I’ve already mentioned rust. This is a worse issue if you live in a humid state or store your mower in a humid place. The second culprit is hitting rocks, bottoming out on dirt, or trying to “mow” some other obstacle such as a garden hose. Even if this doesn’t dull your entire blade, it can flatten a chunk and create long patches on your lawn.

So how do you know if your blades are sharp? Even with work gloves on, you may be able to feel if they are consistently sharp. You can also look at the angle of the blade and see if they are still sharp.

One of the surest ways to tell is to examine your grass. If the ends of the grass are jagged they are more “torn” than “cut.” You can watch these ragged grass ends, which are more susceptible to disease, turn yellow over the days after a mowing. This damage is why grass cut with dull blades takes longer to recover. If you want to avoid neglecting your lawn mower blades–and your grass-it is wise to examine your lawn every time you mow. Even if you only end up sharpening your blades twice a year, at least you’ll know for sure you’re doing it right.

Next, find out whether it is time to service your entire lawn mower, or see a great method for sharpening your blades in the video below:

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Staff Writer

Henry Cesari

Henry Cesari joined MotorBiscuit in 2021 and brings his deep interest in vintage cars, trucks, and motorcycles to the site. Having restored his first classic car at just 16 years old, Henry has wrenched on everything from overland campers to Japanese motorcycles and even pre-war Bugattis. Henry is also an avid attendee at local car shows and genuinely enjoys connecting with fellow auto enthusiasts.

Henry earned a Bachelor’s in Anthropology and English from the University of Vermont. He has since incorporated his love of the written word with his admiration of classic cars. While Henry is interested in vintage cars, he believes the golden age of cars is yet to come. He is confident journalists will play an important role in this revolution by exposing the industry as it is now and envisioning its possible future.