Test Your Knowledge - June

Lawn clippings
A mound of lawn clippings
Karen Russ, HGIC


Lawn clippings are sometimes placed on the side of the street for trash pick up because of the mistaken belief that leaving them on the lawn leads to thatch buildup. Thatch is a dense, spongy collection of living and dead grass stems and roots lying between the soil surface and green grass leaves in established lawns. Leaving grass clippings on the lawn does not contribute to thatch. To learn more about thatch and how to control it, see HGIC 2360, Controlling Thatch in Lawns.

Discarding grass clipping is a waste of organic matter and nutrients that would be beneficial to the lawn. It contains about 4 percent nitrogen, 0.5 - 1 percent phosphorus, 2 - 3 percent potassium, and smaller amounts of other essential plant nutrients - basically a 4-1-3 fertilizer. When left on the lawn, these nutrients are returned to the soil as they break down. For more information on thatch and lawn clippings, see IL 49, Recycle Your Grass Clippings for a Healthier Lawn and Environment.

Grass clippings are also an excellent addition to the compost pile. Grass clippings should ideally be allowed to return directly to the lawn, but if there are clumps of clippings after mowing, add them to your compost bin. In a few months they will be a terrific soil amendment – for free! For more information see HGIC 1600, Composting.

Finally, grass clippings can be used in thin layers as a weed retarding mulch, and will over time add organic matter to the soil. However, do not use grass clippings from a lawn that has been treated with a broadleaf herbicide such as 2,4-D. For more information, see HGIC 1253, Controlling Weeds by Cultivating & Mulching.

Karen Russ
HGIC Horticulture Specialist

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This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.