Summer is the time when lawns tend to look their best, some by chance and others as a result of months spent tending to the grass and soil. Many gardeners will know that lawns can be more volatile or stressed in summer due to higher temperatures and potentially less rainfall. One week, the grass seems green and lush, and the next, it's scorched with unsightly brown patches.

Watering, fertilising and weeding are all important gardening tasks for a healthy lawn, but there's something even simpler that can be done to preserve grass. Lawn mower experts have shared that not checking your mower could be the reason for damaged grass.

Mark Brokaw, John Deere's go-to-market manager for turf parts, told Martha Stewart that uneven grass is one of the first telltale signs that your lawn mower blade needs sharpening.

A blunt blade will not slice grass neatly but tear it up as it goes, resulting in ragged-looking grass rather than a neat mow.

Brown patches on garden grass can occur for a number of reasons, including pest infestations, drought, excessive thatch, soil compaction, and fungal diseases like brown patch. The John Deere turf expert notes that it's also a symptom of a damaged lawn mower.  

Fortunately, you probably don't need to replace your mower; just sharpen the blade. 

How to sharpen a lawn mower blade

The method is simple, but safety is imperative, so first, put on some gardening gloves and start disassembling your mower.

For gas mowers, disconnect the spark plug wire to ensure the engine can't spontaneously start.

Tip the lawn mower on its side so you can access the blade, ensuring that the air filter and carburettor are facing upward. Alternatively, use a lifting device to reach the blade.

Jeff Taylor, product services manager at STIHL, suggests using a short piece of wood, preferably a two-by-four or a four-by-four.

Position the block between the blade and the mower deck. "When I turn the blade counterclockwise, it’s going to stop the blade from turning," said Jeff.

Clean and file the blade

Family Handyman recommends clamping the blade in a bench vice and cleaning off rust and debris with a wire brush.

Before filing, gloves and safety goggles should be worn. A flat file about 10 inches long and half to one inch wide can be used to hone the bevels on both ends of the blade.

Position the file at the exact angle of the bevel and stroke up and down repeatedly while moving from one end of the bevel to the other.

The DIY expert noted: "To maximise the life of the blade, you’re aiming for 'butter-knife' sharp, not razor-sharp. It shouldn’t take more than 30 to 50 strokes to achieve this."

Balance the blade

Before returning the blade to the mower, you must hang it from a nail to check the balance. If one side dips, file a bit more off that side until the blade hangs horizontally, says Family Handyman.

"This step is important because an unbalanced blade causes vibrations that can make mowing more of a chore than it already is and actually damage the lawnmower", they added.

Reinstall the blade

Turn the lawnmower back over, fit the blade onto the shaft, and secure it with the nut or bolt. This time, wedge the wood back between the blade and housing on the opposite side of the blade, then tighten the fastener with the wrench.

Take care to tighten it properly, as leaving it too loose can throw off the engine timing and even make the mower hard to start.

Finally, set the mower upright and replace the spark plug and spark plug wire before giving it a test start.