A mulching lawn mower works by circulating the grass within the lawn mower so that it can be chopped several times before it is dispersed back into your lawn. A mulching lawn mower has a special blade and an enclosed deck to deflect the grass back into the blade. The finely cut grass is then blown down into your lawn instead of being blown out of the side of your mower in large clumps onto your lawn. This approach can also be applied to autumn leaves.
If you do not have a mulching lawn mower, you can use your old mower as a mulching mower. You may have to mow more frequently to make sure you are only removing a small length of grass at a time. You can also cover up the side discharge to keep the grass clippings under your mower, causing them to be chopped more than once. You may be able to adapt your old mower by changing the blade to a mulching style of blade.
Old time reel mowers work well as mulching mowers, as they can only efficiently be used to cut the tips of the lawn, and they do not blow the grass out the side, but rather, drop it back onto the lawn in an even dispersal.
For the best results--whether you are using a mulching mower or a standard mower to mulch your lawn-- be sure to only cut the top third of your grass or less with each mowing. Keep your blades sharp, mow frequently when needed, and only mow when the grass is dry. Raise your lawn mower to a cutting height of 2 - 2 1/2 inches--this will help the cut grass settle into your lawn better.
The mulching lawn mower works to keep your lawn healthier. It naturally fertilizes as it blows the grass down into your lawn. The clippings decompose within days and work naturally as compost for your lawn. Meanwhile you save money on fertilizers, you save time from raking and bagging grass and leaves, and you prevent unnecessary buildup in your local landfill.