How Mulching Blades Work

Function

• Mulching mower blades cut and re-cut the grass clippings, chopping them into ever-smaller pieces like a botanical food processor. The 1/4- to 1/2-inch clippings settle into the lawn and decompose rather than weighing on the grass blades, returning growth-boosting nitrogen and other natural fertilizers to the soil. Standard mower blades cut the grass blades only once, and leave piles of cuttings that, if left unraked or unbagged, smother the underlying grass.

Standard Blades

• With lawn mowers, the term "blade" doesn't refer to a sharp edge but is the rotating rectangular arm that spins under the mower that incorporates a sharp edge to cut the grass. Standard lawn mower blades are straight except for a sweeping, downward curve just before the blade's end. This downward curve carries a sharp cutting edge on the curve's lower side, similar to the design of a snow shovel, and the curve's angle pushes the cuttings to the mower's discharge opening.

Mulching Blades

• Unlike standard mower blades, mulching mower blades have a cutting edge that spans nearly the entire length of the blade, and the blade itself is not straight. The level ends of the blade sit at grass height, while the middle of the blade angles upward to form a central horizontal section. The blade's length also has a slight upward bend opposite the cutting edge. The extended sharp edge, the blade's raised center and the upward bend work together to lift and mince grass cuttings rather than dropping them to the ground.

Deck and Motor

• Manufacturers design mulching lawn mower bodies, or decks, with more room in the cutting chamber than traditional mowers. Mulching blades used in standard mowers often work in cramped conditions and have little room to re-cut grass clippings. Also, mulching mowers generally require a stronger motor. Standard-to-mulching mower conversion kits can work, but don't expect ideal results.