Morning dew is a layer of moisture that forms on grass blades overnight as the air cools. While it is physically possible to mow wet grass, turf management experts strongly advise against it. Mowing with morning dew negatively affects the health and appearance of the turf, the performance of the equipment, and the safety of the operator. Waiting for the grass to dry is the better choice for a healthy lawn.
How Moisture Damages Grass Health
The presence of moisture fundamentally changes how a grass blade interacts with the mower, often leading to a ragged, aesthetically poor cut. Wet grass blades are heavier and more flexible, causing them to bend and lie down under the mower deck instead of standing upright. This results in an uneven appearance once the grass dries and the blades stand back up, giving the lawn a patchy look.
The lack of rigidity means the mower blade is more likely to tear the grass rather than providing a clean cut. This tearing creates a larger wound, increasing the plant’s stress and providing an entry point for pathogens. This damage, combined with moisture, creates an ideal environment for fungal diseases such as brown patch, rust, and dollar spot.
Wet grass clippings tend to clump together instead of scattering evenly. These heavy, sticky clumps can smother the healthy turf underneath, blocking sunlight and airflow. The moist, compacted organic matter acts as a breeding ground for fungal spores, which are easily spread across the lawn by the mower blades.
Equipment Strain and Mower Performance
Mowing wet grass introduces significant mechanical resistance, straining the entire mower system. Heavy, sticky clippings quickly cake onto the underside of the mower deck, the discharge chute, and around the blades. This accumulation restricts airflow, causing the machine to work less efficiently and leading to frequent clogs that require the operator to stop and clear debris.
The increased resistance forces the engine to labor harder, accelerating wear and potentially shortening the machine’s lifespan. This extra work also causes the blade to become dull much faster than when cutting dry grass. A dull blade then exacerbates lawn damage by tearing the grass more severely.
Moisture exposure also increases the risk of corrosion on the mower’s metal components. Wet grass clippings clinging to the deck and undercarriage hold moisture against the metal surfaces, promoting rust formation. This corrosion leads to higher maintenance needs if the mower is not thoroughly cleaned and dried after use.
Operator Safety Hazards
Mowing wet grass introduces immediate risks to the operator. The saturated turf makes the ground surface slick, increasing the danger of slipping and falling, especially on sloped terrain. Loss of footing can lead to serious injuries if the operator falls onto or near the moving blades.
For those using electric mowers, the presence of dew poses a serious electrical hazard. Water increases the risk of electric shock, making operation in damp conditions dangerous. Operators must wait for the lawn to dry completely before using an electric machine.
Wet grass clippings are thrown further and stick more readily to surfaces, which can momentarily obscure the operator’s vision. These clippings can coat safety glasses or protective shields, creating a temporary loss of visibility.
Determining the Best Time to Mow
Scheduling the chore for the right time is the simplest method to ensure a clean cut and maintain a healthy lawn. The best window for mowing is typically mid-morning, generally between 8:00 a.m. and 10:00 a.m., after the morning dew has completely evaporated. This timing ensures the grass is dry, allowing the blades to stand fully upright for a clean trim, and avoids the peak heat of the day, minimizing heat stress.
A simple way to test if the lawn is dry enough is to walk across the grass. If the soles of your shoes remain dry and you do not leave dark footprints, the grass is ready to be cut. Waiting for the surface moisture to dissipate allows the mower to perform optimally and prevents the spreading of disease.
If mowing when the grass is slightly damp is necessary, a few precautions can minimize damage.
Precautions for Mowing Damp Grass
Raising the cutting height on the mower deck reduces the amount of grass being processed at once, lessening the chance of clogging and tearing. Moving at a slower speed also allows the blades more time to process the heavier clippings, resulting in a slightly better cut.