While a lawnmower can technically pass over a wet lawn, this action is generally discouraged by turf management professionals. Wet grass refers to blades covered in morning dew, residual moisture from a recent rain, or turf sitting atop saturated soil. Proceeding with mowing under these conditions introduces several complications that compromise the health and appearance of the lawn, as well as the longevity of the equipment. Waiting for the grass to dry completely allows the blades to stand upright, ensuring a clean cut and preventing issues.
The Immediate Risks to Your Lawn
Mowing wet grass significantly increases the likelihood of an uneven and ragged cut that stresses the plant. When the grass blades are heavy with moisture, they tend to bend over rather than stand rigid, causing the mower blade to tear the plant tissue instead of slicing it cleanly. These torn, frayed ends create an entry point for pathogens and cause the tips of the grass to turn brown as they die back.
The moisture also causes clippings to clump together into dense, sticky masses instead of dispersing evenly across the turf. These thick clumps fall onto the lawn surface, blocking sunlight from reaching the healthy grass underneath and smothering the turf, which can lead to dead patches. Furthermore, the combination of wounded grass and prolonged moisture creates an ideal environment for the spread of fungal diseases.
The mower blades and deck can pick up and transmit fungal spores, such as those responsible for brown patch or red thread, across the entire lawn surface. Operating a heavy machine on water-saturated soil also leads to soil compaction, reducing the pore space needed for air and water to reach the grassroots. This compaction inhibits root growth and can ultimately cause visible ruts from the mower’s tires, permanently damaging the lawn’s smooth surface.
Potential Damage to Mowers and Equipment
Wet grass clippings are denser and stickier than dry ones, causing them to adhere quickly to the underside of the mower deck. This accumulation of material restricts the necessary airflow beneath the deck, which is required to lift the grass blades for a clean cut and properly discharge the clippings. The reduced airflow and increased drag force the engine to work harder, causing it to strain, bog down, or even stall.
Cutting heavy, wet material accelerates the dulling of the mower blades, requiring more frequent sharpening to maintain an effective cutting edge. The constant exposure to moisture also promotes rust and corrosion on the metal components of the deck and blades. If the mower is not cleaned immediately, the caked-on, wet material will trap moisture against the metal surfaces, leading to premature wear and potential failure of moving parts.
Operator safety is also a concern when mowing in damp conditions, as wet grass creates a slippery surface, increasing the risk of slipping, especially on slopes. For individuals using a corded electric mower, the presence of water introduces a serious electrical hazard, raising the potential for a dangerous shock. Even battery-powered mowers can be compromised if water breaches the housing and affects the internal electrical components.
Techniques for Mowing Damp Grass Safely
If mowing cannot be postponed until the lawn is completely dry, several precautions can be taken to minimize damage to the turf and equipment.
Preparation and Cutting
The most important step is ensuring the mower blades are sharpened to a razor-edge to reduce the tearing of the wet grass blades. A clean, sharp cut allows the plant to seal the wound more quickly, which lowers the risk of fungal infection.
It is advisable to raise the cutting deck to its highest setting, which reduces the amount of material being processed in a single pass. This decreased load allows the engine to maintain a higher blade speed, improving the quality of the cut and reducing the likelihood of clogging. Mowing at a slower pace than normal is also recommended to give the blades more time to cut through the heavy, waterlogged grass.
When making passes, use a greater overlap than usual to ensure all the bent-over blades are cut, preventing large, visible strips of uncut grass.
Post-Mowing Cleanup
After the work is complete, it is imperative to immediately and thoroughly clean the underside of the mower deck, removing all wet clippings. This immediate cleanup prevents the clippings from hardening into a cement-like layer and mitigates the risk of rust and the growth of mold or fungi on the machine.