The annual fall leaf drop presents a choice: spend hours raking and bagging organic material or recycle the leaves directly into your lawn. Mowing leaves—a process known as leaf mulching—is a highly effective and time-saving alternative that benefits turf health. When leaves are finely shredded and returned to the lawn, they decompose, releasing valuable nutrients like nitrogen, phosphorus, and potassium back into the soil, essentially acting as a natural, slow-release fertilizer. This practice also enriches the soil with organic matter, improving its structure and capacity to retain moisture and support beneficial microbial activity.
Preparing the Mower and the Lawn
You should only attempt to mulch dry leaves, as moisture causes them to clump together, leading to poor shredding, clogging the mower deck, and potentially smothering the grass beneath. Before starting, clear the area of any large sticks, rocks, or other debris that could damage the mower blades or be ejected at high speed.
The sharpness of the mower blade is a major factor in achieving the fine particle size required for quick decomposition. A dull blade tears the leaves instead of cleanly chopping them, slowing the breakdown process. While standard blades can work, using a dedicated mulching blade, often called a “Gator” blade, can significantly improve performance by creating more lift and multiple cutting surfaces.
You should set the mower deck to its highest cutting height, or at least one level above your normal setting, for the first pass. A higher deck allows the leaves to cycle longer within the housing, increasing the chance of being chopped into small fragments. For a mulching operation, the bagger attachment should be removed, and if your mower has a side discharge chute, it should be closed or plugged to keep the shredded material contained under the deck for maximum cutting action.
The Optimal Mulching Technique
The physical act of mulching requires a specific approach to ensure the leaves are reduced to the correct size and distributed evenly across the turf. You should operate the mower at a slow walking speed, moving slower than you would during a typical grass-only cut. This deliberate pace ensures the mower’s blades have enough time to draw the leaves up and chop them repeatedly before they are dispersed onto the lawn.
The goal is to reduce the leaves to pieces roughly the size of a dime or smaller, which allows them to filter down through the grass blades to the soil surface. If the shredded leaves are still visibly large or are lying heavily on top of the grass after the first pass, you will need to perform a second pass. A crisscross pattern, where the second pass is perpendicular to the first, is highly effective for reducing particle size and ensuring uniform coverage across the area.
After mulching, the finely chopped leaf material should not completely obscure the grass below. If the turf is still easily visible, the leaf “confetti” will quickly settle and begin to break down, providing the intended nutrient benefit. Frequent, light mulching is far more effective than trying to manage a deep layer all at once, as it prevents the shredded material from forming a mat that could block sunlight and air from reaching the grass.
Strategies for Heavy Leaf Layers
When the layer of fallen leaves is exceptionally heavy, the standard mulching technique may be insufficient and could potentially harm the turf. A thick, matted layer of mulched leaves can block sunlight and moisture, potentially smothering the grass. In these situations, a staged approach is necessary to prevent these issues.
Instead of trying to shred the entire volume, you can make multiple passes, gradually lowering the mower deck height with each pass. Alternatively, you can collect the excess material by attaching the bagger after the initial shredding passes, as the leaves are already partially broken down.
The excess shredded leaves should not be discarded. They can be spread in flower beds and around shrubs to serve as a high-quality garden mulch, which helps to conserve soil moisture and suppress weed growth. They can also be added to a compost pile, where the reduced particle size will accelerate the composting process.