November 1996 - Volume III, Issue 11

The Mystery of the Mulching Mower

David M. Kopec, Extension Turfgrass Specialist

Mulching mowers have been around for some time now and almost every major manufacturer offers models for sale to the general public. There are almost as many myths about mulching mowers, as there are mysteries (more like bad traditions) about proper mowing techniques. Heres the scoop!

Mulching Mowers - - what they do
Mulching mowers are designed to do two things. Cut the grass (like any other rotary mower does) and too shred the leaf blades into very small pieces. The "benefits" of this second (mulching) feature is less visible clippings and increased rate of clipping decomposition (from shredding).

Mulching mowers accomplish this by the use of special blades and unique mower deck designs which increase swirling (hang-time), so that the clippings are suspended longer and are cut more times by the blade. That's what a mulching mower does.

Here's what they do not do or in more applicable terms, here's some incorrect arguments or assumptions about their use.

"I can mow lower now since I have a mulching mower." This statement is incorrect. Turfgrass cultivars have specific recommended mowing heights, which is a function of leaf width, shoot density and internode length. Mowing below the lowest tolerable base height is still not achievable, regardless of the mower type used. No more than one third of the vegetation should be mowed off at any single mowing event. When you break this rule, you scalp the turf and this is extremely detrimental.

"I can mow less frequently since I am using a mulching mower." This statement is also incorrect. Think about the one third rule! If you mow less frequently, the grass is taller the next time you mow it. This causes scalping, regardless of the mower type. With a mulching mower you see less clippings, so it's a temptation to mow less frequently. This is really a "lazy mans" use of a mulching mower. This practice will weaken the turf and is not a valid use of a mulching mower.

"I can mow wet grass with a mulching mower without any problem." Another false statement. While mulching mowers will leave less clippings behind on wet grass, it is an unwise practice to do so. The underside of the deck will "clump up" very quickly. This negates the air-deck aerodynamics which are necessary for proper mulching.

Mulching mowers are excellent choices for most lawns. They re-cycle valuable nutrients (about 10-15% of the lawns requirement) and save valuable land-fill space which is needed for other items in our disposable society.

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