Mulching lawnmowers are one of those rare places where convenience and conscience meet. A mulching mower is specially designed to slice grass clippings into very fine particles, which are then left on the lawn. Unlike normal grass clippings, these fine particles do not have to be hauled away and do not form unsightly clumps. They decay quickly and are naturally reabsorbed into your lawn, nourishing the grass, saving the energy it would take to pick them up and transport them to a recycling center and allowing you to nourish your lawn with less fertilizer.
Mow your lawn with the mulching function engaged on dry days, at least 24 hours after a significant rainfall. Wet clippings will clump and not mulch as well.
Mow your lawn every five to seven days. To keep your lawn healthy and generate good mulch, your mower should only remove 1/3 of the length of a blade of grass every time you mow.
Turn off the mulch function when it is wet outside and bag your clippings instead. This will prevent clumps of grass clippings from accumulating on your lawn.
Reduce your use of fertilizer by one-third. According to Grounds-mag.com, mulching mowers add nitrogen and other nutrients back to the soil, decreasing the need for fertilizer.
Bag your clippings on wet or cold days. This will prevent them from building up a layer of debris on the lawn.
Run the mower over your lawn an extra time if a layer of debris does build up. The mulching mower will suck it out of the lawn and grind it into finer clippings.