Grass clippings are the organic material resulting from the mowing of turfgrass. While often viewed as yard waste requiring disposal, they represent a valuable, readily available organic resource. Understanding the composition and proper management of this byproduct can lead to a healthier lawn and a reduction in waste volume.
Composition and Basic Definition
The physical and chemical makeup of grass clippings makes them beneficial for soil health. Fresh clippings have a high water content, typically 80 to 90 percent by weight, which causes them to decompose very quickly.
Clippings are rich in the elements necessary for plant growth, containing substantial nitrogen, phosphorus, and potassium. This nutrient content classifies them as a “green” material in composting terms. Returning this material to the soil can provide up to 25 percent of a lawn’s annual fertilizer needs.
Handling and Management on the Lawn (Grasscycling)
Leaving grass clippings on the lawn after mowing is a practice known as grasscycling, which naturally recycles nutrients. This technique allows the organic matter to break down and return essential elements directly to the soil. Grasscycling reduces the need for supplemental fertilizers and the amount of yard waste sent to landfills.
The correct technique for successful grasscycling involves specific mowing habits. It is recommended to follow the one-third rule, meaning you should never remove more than one-third of the grass blade length in a single session. This ensures the clippings are small enough to filter down and decompose quickly.
Mowing frequency must be adjusted during peak growing seasons to maintain this rule. Using a sharp mower blade is also important, as a dull blade tears the grass, creating rough, jagged edges that can turn brown. Contrary to a common misconception, grass clippings do not contribute to the formation of thatch.
Excessive accumulation of clippings should be avoided, as large, wet clumps can smother the turf and lead to fungal diseases. If the grass has grown too tall, raise the cutting height and mow over the area a second time to shred and scatter the material evenly.
Alternative Uses (Off-Lawn Utilization)
When grass clippings are collected, they can be repurposed in other areas of the landscape. One beneficial use is adding them to a compost pile, where their high nitrogen content acts as an accelerator for decomposition. Fresh clippings are considered a “green” component and must be balanced with “brown” materials, such as dried leaves or straw, to prevent the pile from becoming overly wet and anaerobic.
Clippings can also be used as a garden mulch to conserve soil moisture and suppress weed growth. When used for mulching, the clippings should be spread in a thin, dry layer, ideally no more than one to two inches deep. Applying a thick or wet layer can cause the material to mat together, inhibiting the movement of oxygen and water to the soil below.
A significant precaution involves avoiding clippings from lawns recently treated with herbicides, especially for edible gardens. Certain persistent herbicides may not break down sufficiently during composting or mulching and can potentially harm susceptible plants. It is best to wait for two or three subsequent mowings after an herbicide application before using the clippings.