The question of whether grass clippings should be collected or left on the lawn is common for homeowners. The practice of leaving clippings on the turf to decompose is known as grasscycling, which recycles organic matter back into the soil. For most lawns, leaving the clippings is highly beneficial for the turf’s health and vitality. This simple, nature-based approach transforms yard waste into a valuable resource, promoting a more self-sustaining ecosystem and supporting a lush, dense carpet of grass.
The Fertilizing Power of Grass Clippings
Grass clippings act as a natural, slow-release fertilizer for the turf. They are composed of 75% to 85% water, allowing them to break down rapidly once they settle into the lawn. This quick decomposition returns essential elements, primarily nitrogen, back to the soil for reabsorption by the grass roots. A typical clipping contains about 4% nitrogen, 2% potassium, and 0.5% phosphorus by dry weight, providing balanced, continuous feeding.
Consistent grasscycling can supply a significant portion of the lawn’s annual nutrient requirement, potentially reducing the need for commercial nitrogen fertilizer applications by up to 25%. The decomposing clippings also contribute organic matter that improves soil structure and enhances water retention, helping the turf remain hydrated during dry periods.
Addressing the Thatch and Disease Myths
A long-standing misconception is that leaving grass clippings creates a thick layer of thatch that chokes the lawn. Thatch is a layer of slowly decomposing, dense organic material made up primarily of dead grass stems, roots, and rhizomes. Grass clippings, however, are mostly water and have a low carbon-to-nitrogen ratio, meaning soil microorganisms quickly consume them. Properly managed clippings do not contribute to thatch buildup because they decompose too quickly to accumulate. The real causes of excessive thatch are often compacted soil, over-fertilization, or improper mowing.
Another concern is that grasscycling spreads lawn diseases, but this is only relevant in specific circumstances. Fungal spores can be transported by clippings, but only if the lawn is suffering from an active, severe disease outbreak. If the turf is generally healthy, the practice is safe. When the lawn is actively infected, collecting the clippings is a sensible temporary measure to prevent spore dispersal.
Essential Mowing Techniques for Grasscycling
Successful grasscycling relies on adopting practical mowing techniques to ensure clippings are fine and evenly dispersed. The primary rule is the “one-third rule,” which dictates that no more than one-third of the grass blade’s total height should be removed in a single session. Adhering to this principle ensures the clippings are small enough to filter down to the soil surface quickly.
Following this rule often requires increased mowing frequency, especially during peak spring growth. It may be necessary to mow twice a week rather than once to manage the rapid growth and avoid excessive clipping length. Furthermore, the mower blade must be kept sharp. A dull blade tears the grass, stressing the plant and creating ragged edges. Using a sharp or specialized mulching blade finely shreds the clippings, enhancing their ability to decompose quickly.
Situations Where Bagging is Necessary
While grasscycling is the recommended practice, collecting clippings is necessary in specific instances. The primary exception is when the grass has grown excessively long, violating the one-third rule. The resulting large volume of clippings will clump and mat on the surface, smothering the turf and blocking sunlight. In this situation, the clippings must be bagged and removed to prevent damage to the grass below.
Collecting clippings is also prudent if the lawn exhibits signs of active fungal disease, such as rust or dollar spot. Removing infected clippings minimizes the risk of spreading spores to healthy sections. Finally, if the lawn has a significant presence of weeds that have gone to seed, bagging prevents the distribution of those seeds across the yard. Once these issues are resolved, homeowners can immediately return to grasscycling.