Clumps of grass clippings on the lawn are not only unsightly -- they can damage or even kill the lawn grass. When your push mower leaves clumps of grass clippings on the lawn as you mow, the likely causes are wet grass or allowing the grass to get too tall before you mow. You can't control the weather, but you can maintain a healthy, clump-free lawn by making a few changes in the way you mow the lawn. Suggested turfgrasses for mild, Mediterranean climates include Bermuda (Cynodon dactylon, U.S. Department of Agriculture plant hardiness zones 7 through 10), and Zoysia (Zoysia japonica, USDA zones 5 through 10).
Mowing when the grass is wet doesn't damage the grass, but the clumps left on the lawn are unsightly and can cause problems if they aren't removed. Mowing when the grass is too tall is more likely to damage the lawn than mowing when it is wet, so you may find that you have to mow wet grass from time to time. On these occasions, remove the clumps promptly.
To prevent clumps from long clippings, never remove more than one-third of the length of the blades of grass at one time. For example, to maintain a lawn at a height of 2 inches, let the grass grow until the blades are 3 inches tall before you mow. If you have to let it grow taller than usual because of rain, remove one-third of the length of the grass twice a week or so until you reach the desired height.
Effects of Grass Clumps
Leaving grass clippings on the lawn after mowing can supply as much as 25 percent of the annual fertilizer needs, so it's best to leave them on the lawn unless they are clumped. Clumps of clippings block sunlight and cause yellow leaves. Remove clumps of clippings by raking or mowing over them again in a day or two when they are dry. If you make a habit of leaving clumped clippings on the lawn, the grass may eventually die.
Push Mower Blades
Mulching blades chop the clippings into finer pieces than regular push mower blades. Finer clippings are less likely to clump, and they break down faster than longer clippings. Dull blades tear the grass rather than cutting it and give the grass a brownish cast, so keep the blades sharp. Torn grass also encourages disease and increases fuel consumption when you mow.
- UMass Extension Center for Agriculture: Lawn Mowing
- University of Kentucky Cooperative Extension Service: Mowing your Kentucky Lawn
- University of Minnesota Extension: Lawn Clipping Management
- Ohio State University Extension: Mowers and Mowing
- Kansas State University Agricultural Experiment Station and Cooperative Extension Service: Mowing Your Lawn
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