While it is physically possible to push a mower across a lawn covered in morning dew, turfgrass experts strongly discourage it. Dew is condensed atmospheric moisture that settles on the grass blades overnight, making the entire lawn surface wet and heavy. Mowing under these conditions introduces numerous problems for the health of the turf and the performance of the equipment. For a healthy, well-maintained lawn, it is better to wait until the grass has dried completely.
How Moisture Damages Grass Blades
Mowing wet grass can cause immediate and long-term damage to the turf itself, compromising the lawn’s appearance and its resistance to disease. The water causes the individual grass blades to become saturated, heavy, and flexible, which makes them lie down instead of standing upright for a clean cut. The mower blade then tends to tear and rip the wet, pliable tissue rather than slicing it cleanly, resulting in ragged, stressed ends.
These torn ends can turn white or brown shortly after the cut, creating a noticeable discoloration across the lawn’s surface. A torn blade creates a larger wound than a clean cut, leaving the plant more vulnerable to external pathogens. Wet conditions provide the ideal environment for fungal diseases, such such as Brown Patch or Dollar Spot, to thrive.
Mowing a wet lawn actively spreads fungal spores around the yard, as the mower’s deck, blades, and tires pick up moisture and existing fungal material. Wet grass clippings clump together rather than dispersing evenly. These heavy clumps can smother the underlying turf, blocking sunlight and air circulation, which creates more spots where disease can take hold.
Mower Performance and Maintenance Issues
The presence of moisture significantly degrades the mechanical performance of the mowing equipment. Wet grass clippings are sticky and quickly adhere to the underside of the mower deck, creating a thick, caked-on layer. This accumulation restricts the necessary airflow that helps the blades lift the grass for a uniform cut, severely reducing the mower’s efficiency.
The decreased airflow and the weight of the wet material force the engine to work much harder to maintain blade speed, leading to strain, overheating, and potential stalling. For mulching or bagging mowers, the wet clippings rapidly clog the discharge chute, making it difficult or impossible to dispose of the cut grass. This clumping often requires the operator to stop frequently to scrape the deck clean.
Beyond immediate performance issues, long-term maintenance is affected by mowing wet turf. The prolonged exposure to moisture and trapped organic material accelerates rust and corrosion on metal components, particularly the mower deck and the blade assembly. Cleaning the caked-on, compacted wet grass from the machine is also considerably more difficult and time-consuming than simply brushing away dry clippings.
Optimal Conditions for Cutting the Lawn
The best practice for lawn health and equipment longevity is to mow only when the grass is completely dry. The ideal time for this is typically mid-morning, after the dew has evaporated but before the intense heat of the midday sun. This timing allows the turf sufficient time to recover from the cut before the cooler, damp conditions of evening return, which helps prevent fungal growth.
A simple visual inspection can confirm the grass is dry, but running a hand through the turf to check for lingering moisture is a more accurate test. If your shoes or pants become visibly wet from walking through the grass, it is still too soon to mow. Waiting until the grass is dry also significantly improves operator safety, as wet grass is notoriously slippery, increasing the risk of slips and falls, especially when operating a mower on any incline.
If circumstances require mowing slightly damp turf, raising the cutting height and moving at a slower speed can help reduce strain on the mower and minimize tearing the grass blades. This approach reduces the impact on the machinery and the turf.