Tips on Mulching Mowers and Grasscycling

Terminology  In composting literature, the terms ‘grasscycling’ and ‘grass recycling’ are used to refer to the process of mowing grass finely and allowing it to fall back onto the lawn rather than removing it.

Most mower manufacturers use the term ‘mulching’ rather than ‘grasscycling’. On equipment and in their literature the terms 'mulching mower' or ‘grass mulching capacity’ are used.

The Key to Grasscycling: Mulching Mowers

How do they work?  A mulching plug or flap is used to block the exit portal for cut grass. This exit is the discharge opening where the grass catcher would otherwise be attached. With the plug or flap in place the grass continues to swirl underneath the platform, being shredded more finely until it drops onto the lawn. These clippings protect the stem and root structure of the lawn from drying out, and act as a cushion. When the clippings break down, the roots can then absorb their nutrients.

Most lawn mowers manufactured since 1995 have the mulching feature. Before that, this was a design feature of only some models. Mulching blades are often sold as extras, but keeping the original mower blade sharp is less wasteful and less expensive. It’s important to maintain a sharp blade for effective grasscycling. Adapting older mowers Older mowers without the mulching feature can be adapted by covering the mower’s outlet spout. Converting an old mower will depend on the tools, skills and eye for design of the home owner.

Grasscycling Tips

Be aware  Grasscycling requires close awareness and attention to what is going on with the lawn and with the mowing procedure itself.

Mow more often, particularly in the spring and early summer when the grass grows quickly. A well watered and heavily fertilized lawn may need mowing two to three times a week.

Take less off at each mowing  A good rule of thumb is never to take off more than an inch and a half at one time. Taking more off, especially when the grass is lush, can result in the clippings clumping together under the mower and dropping onto the lawn. Grass left like this is a less effective mulch as it stays on top of the lawn rather than getting down to the roots. Persistent mowing of this nature can be harmful to the lawn.

Go slowly.  Even when taking off small amounts, clumping may result. If this happens, walking more slowly may solve the problem.

Don’t scalp the lawn  Grass cropped to an inch or two high demands more water and fertilizer to stay in good condition, and defeats the purpose of the mulching mower. A three-inch grass blade is optimal. Most mowers have a height adjustment device at the wheels that allows you to raise the blade.

Did the grass grow under your feet?  For whatever reason - holidays, sickness, busyness - the grass may get beyond the mulching capacity of your mower. If this happens, mowers with a side discharge may help. Open the side discharge when mowing over long grass. This will throw the grass to the side and on top of the lawn. Mow over it a second time with the mulching plug or flap in place. The mower will pick up the cut grass and shred it.

To grasscycle or not  It’s not an all-or-nothing proposition. For instance, even if you don’t compost, removing lawn cuttings at certain times can function as a weed control measure, e.g. at the time dandelions are setting seed. So grasscycle when it suits, and look for other options when it doesn’t.

March 2008

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