It is a common dilemma: the lawn has grown too long, but recent rain or heavy morning dew has left the grass damp. While the temptation to keep to a schedule is strong, mowing wet grass is generally discouraged. This practice introduces significant risks that can negatively impact the health and appearance of the turf, strain equipment, and compromise the safety of the operator.
Detrimental Effects on Turf Quality
When grass blades are saturated with water, they lose their rigidity and tend to bend or fold under the pressure of a mower deck. This pliability prevents the spinning blade from making a clean, sharp cut, resulting instead in a tearing or shredding action that leaves jagged tips. These torn ends give the lawn a ragged, grayish-brown appearance and create open wounds that make the plant more vulnerable to disease and pests.
The moisture also encourages grass clippings to clump together beneath the mower deck and across the lawn surface. These heavy, wet clumps can smother the turf underneath by blocking sunlight and air circulation, leading to patches of yellow or dead grass. Furthermore, the presence of excessive moisture and open wounds creates an ideal environment for fungal diseases, such as brown patch or leaf spot, which can spread rapidly.
Operating a machine over saturated soil also leads to soil compaction. The pressure from the mower wheels compresses the soil particles, reducing the pore space needed for air and water to penetrate to the root zone. This compaction suffocates the grass roots by limiting their access to oxygen and nutrients, hindering growth and potentially causing ruts or uneven surface damage in the lawn.
Hazards to Equipment and Personal Safety
Mowing wet grass places considerable strain on the machine, often leading to performance issues and potential damage. The sticky, dense wet clippings quickly build up and clog the discharge chute and the underside of the mower deck. This accumulation forces the engine to work harder to maintain blade speed, leading to overheating, reduced efficiency, and unnecessary wear on the motor components.
The added resistance from the heavy, wet vegetation can also cause the blades to slow down, making the cutting action less effective and accelerating the dulling process. For corded electric mowers, the presence of water introduces an electrical shock hazard. Even for gasoline-powered and battery-operated machines, excessive moisture can cause components to corrode over time if the machine is not cleaned immediately after use.
Personal safety is also jeopardized when mowing in damp conditions. Wet grass and soil create a slippery surface, dramatically increasing the risk of the operator slipping and falling, particularly on slopes or uneven terrain. A loss of footing can lead to serious injury, including the possibility of slipping under the moving mower deck. It is also more likely that an operator will attempt to clear a clogged discharge chute by hand while the engine is still running, which is a common cause of severe injury involving the rotating blade.
Mitigation Techniques and Waiting Strategies
The most straightforward strategy is to wait until the grass has completely dried, which usually occurs late morning or early afternoon after the dew has evaporated. If a delay is impossible due to overgrowth, one technique is to drag a hose or broom across the lawn to knock off some of the surface moisture before starting. This action can help accelerate the drying process for the grass blades.
Should mowing slightly damp grass be unavoidable, raise the mower deck one setting higher than the usual cutting height. Cutting a smaller amount of the grass blade reduces the volume of wet material entering the deck, which helps minimize clumping and engine strain. Moving at a slower walking pace also gives the blades more time to clear the dense, wet clippings and prevents the mower from getting bogged down.
After cutting damp grass, cleaning the machine is an immediate necessity to prevent long-term damage. The underside of the mower deck should be scraped and hosed down to remove all packed-on clippings, as these moist organic materials can promote rust and corrosion. Maintaining a very sharp blade is important, as a clean cut is the only way to reduce the stress and vulnerability of the turf.