Mowing grass that is too wet is a common error that damages the health and appearance of the turf. It also negatively affects the performance and longevity of the mowing equipment. Determining if the lawn is “dry enough” requires assessing moisture levels on the blades and within the soil, not just checking for active rainfall.
Identifying Dry Grass
Assessing the grass blades is the most reliable way to check if the lawn is ready. When grass is dry, the blades appear matte and stand upright, allowing the mower’s blade to deliver a clean cut. Conversely, wet grass often has a noticeable sheen, and the blades droop under the weight of the moisture.
A practical method for determining dryness is the “footprint test.” Walking across the lawn and observing the grass can reveal its readiness for mowing. Dry grass possesses turgor pressure, causing the blades to spring back quickly after being stepped on.
If your footprints remain visible for more than a few seconds, the grass is likely too wet, or the soil beneath is too saturated. This lack of immediate rebound suggests the grass is either heavy with moisture or already experiencing drought stress. Ideally, you should wait until mid-morning or early afternoon to mow, which allows dew or light overnight irrigation to evaporate fully.
Waiting at least 24 hours after rainfall ensures moisture has dissipated from the blades and soil. Mowing immediately after an irrigation cycle or a heavy morning dew is ill-advised. The goal is to see blades that are fully vertical and free of surface water before starting the engine.
The Risks of Mowing Wet Grass
Mowing wet grass results in an uneven cut because the moisture causes the blades to bend and fold over, rather than standing up straight. The result is a ragged, patchy appearance that becomes noticeable once the grass dries and stands back up.
Wet grass clippings clump into dense mats instead of dispersing evenly. These clumps can smother the healthy turf beneath them, blocking sunlight and air circulation. This creates a moist, stagnant environment that promotes the growth and spread of harmful fungal diseases, such as brown patch or leaf spot.
The added weight of saturated grass strains the mower’s engine, forcing it to work harder and potentially leading to premature wear. Wet clippings also cling to the underside of the mower deck, which can clog the discharge chute and reduce lift, decreasing cutting efficiency. The weight of the mower moving across saturated soil can also cause deep ruts and lead to soil compaction.
Soil compaction restricts the space available for oxygen and water penetration, which chokes the grass roots and hinders nutrient uptake. Wet grass is also slippery, presenting an increased safety hazard for the operator, particularly on slopes or uneven ground. Wet conditions can accelerate rust and corrosion on the mower’s metal components.
Operational Adjustments for Damp Lawns
When conditions make it impossible to wait for the lawn to dry completely, a few operational adjustments can mitigate the damage. Using a newly sharpened blade is important when dealing with damp grass. A dull blade will tear the moist grass, leaving a frayed, open wound susceptible to disease.
Raising the mowing height by one setting above the normal level is advisable when cutting damp turf. This reduces the volume of grass entering the deck at one time, minimizing the chance of clumping and engine bogging. Decreasing the walking speed also allows the blade more time to clear the heavier, wetter clippings.
If your mower has a mulching function, switch to bagging the clippings when the grass is damp. Wet clippings do not break down efficiently and will form smothering clumps if left on the lawn. For slightly damp conditions, overlapping each mowing pass by approximately 50 percent can help ensure a more uniform cut by re-cutting any straggling or bent blades.