Mulching blades use additional cutting surfaces along a curved blade, or multiple blades, to turn grass into mulch before depositing it back on the ground. Sometimes known as three-in-one blades, these differ from standard two-in-one blades that cut grass and send it toward a grass catcher.
Mulching blades on a lawn mower usually feature more curved surfaces and additional cutting edges along the blades. Some mulching mowers feature two blades installed perpendicular to one another that rotate together to increase the amount of mulching. Newer mulching mowers have single blades that feature a greater degree of curvature and even more cutting surface to provide optimal mulching. Whether in a dual- or single-blade system, mulching mowers keep the grass moving along the blades for a longer period of time. This makes longer pieces and clippings that are small enough to decompose quickly.
The purpose of mulching grass is to allow clippings to release their nutrients back into the soil. This eliminates the need to bag grass clippings and send them to landfills; instead, the environment benefits because plastic bags take decades, if not longer, to decompose. Instead, grass that is mulched decomposes quickly, provides soil nutrients and keeps that plastic out of the environment.