A lawn mower with a dull blade can lead to disease problems in your lawn … and takes more time to mow! Source: turf.purdue.edu
Lawn mower blades become dull over time and soon begin to tear off the tips of the blades of grass rather than slicing them off neatly. This leaves a ragged edge that gives the lawn a brownish cast and also opens the door wide to lawn grass diseases. A lawn mower with a dull blade also requires more effort to push and makes for slower mowing, often forcing you to remow certain sections.
How do you know if the blade needs sharpening? After you mow, pull out a blade of grass. If the end is neatly trimmed, the blade is still doing its job. If you see a ragged edge, the blade is too dull.
A dull lawn mower blade is easy enough to correct. Just make a habit of sharpening your mower blade occasionally. For most lawns, once a year is fine, but if you have a large area to mow, a second sharpening in mid-season may be necessary.
Here’s a video that explains how to sharpen a mower blade using a grinder. The same operation can be done using a simple metal file as well. And if you don’t want to do it yourself, there are shops specializing in sharpening mower blades pretty much everywhere.
Sometimes a little effort now allows you to be more laidback later!