The first mow of the season dictates the health and appearance of your lawn for the entire year. Cutting the grass too early or too late, or using the wrong technique, can stress the turf as it emerges from winter dormancy. Proper timing and preparation signal the beginning of the active growing period and encourage a dense, resilient stand of grass.
Timing Based on Grass Type and Temperature
The calendar date is not a reliable indicator for when to start mowing; the true signal for grass growth comes from the soil itself. Grass plants emerge from dormancy once the ground reaches a specific temperature threshold. Using a soil thermometer to check the top few inches offers the most accurate reading for this trigger.
Cool-season grasses, which include varieties like Kentucky bluegrass, fescue, and perennial ryegrass, begin to wake up when the soil temperature consistently reaches about 55°F. This temperature activates the plant’s internal processes, allowing it to begin nutrient uptake and leaf production. Mowing should commence only after this consistent temperature is reached and visible growth has begun.
Warm-season grasses, such as Bermuda and Zoysia, require more heat to begin their active growth phase. These varieties wait until soil temperatures stabilize between 60°F and 70°F. Mowing these grasses before they reach this warmer range can damage the turf and inhibit their ability to green up fully.
Physical Signs Your Lawn is Ready
Beyond measuring the soil temperature, the most direct way to know your lawn is ready is by observing the height of the grass blades. The general rule for the first cut is to wait until the grass has reached approximately three to four inches. This ensures the plant has sufficient leaf surface area for photosynthesis, which fuels strong root development in the spring.
Adhering to the “one-third rule” is important during the first mowing session. This rule states that you should never remove more than one-third of the total blade height in a single cut. For instance, if your grass is four and a half inches tall, cut it down to three inches. Cutting more than this can shock the plant, causing it to expend stored energy on leaf repair instead of root growth.
The lawn needs to show evidence of vigorous, new growth, not just the residual brown tips left over from winter. If the turf is matted down or exhibits only sparse, scattered green shoots, wait a little longer. The grass should be standing upright and actively growing before you introduce the stress of the mower.
Preparing the Lawn for the First Mow
Before starting the mower, inspect the lawn surface to eliminate any hazards accumulated over the colder months. Winter weather often leaves behind sticks, loose stones, pet toys, and other debris that can be ejected by a spinning blade. Clearing this material prevents damage to your equipment and ensures a safer mowing experience.
Checking the soil moisture level is necessary before the initial cut. You should be able to walk across the lawn without leaving deep footprints. Mowing wet grass can lead to problems, including tearing the blades instead of cleanly slicing them, which leaves the grass susceptible to disease. Wet clippings also tend to clump and can smother the grass, causing yellowing and dead patches.
The firmness of the soil indicates its moisture content and ability to support the mower without creating ruts. If the ground is still soggy, the wheels can compress the soil, leading to compaction that hinders root growth and water penetration. A dry, firm surface allows for a cleaner cut and healthier recovery.
Technique for the Initial Cut
The quality of the initial cut is determined by the sharpness of the mower blade. A freshly sharpened blade delivers a clean cut, promoting faster healing. A dull blade rips and shreds the ends of the grass, leaving a jagged surface that turns white or brown and creates an entry point for fungal diseases.
When setting the cutting height for the first pass, use the highest setting possible on your mower deck. Starting high encourages the grass to grow deeper roots by shading the soil, which helps to conserve moisture and suppress weed germination. This practice minimizes stress on the plant during its spring emergence.
For managing the clippings, you can choose between mulching or bagging, depending on the volume. If the grass height is only slightly above the target and you followed the one-third rule, mulching the clippings returns nutrients to the soil. However, if the growth is excessive and the clippings form large clumps, bagging is recommended to prevent smothering the new growth.
After the first cut, you may need to increase mowing frequency to every four or five days until the lawn is consistently maintained at the desired height. This frequent cutting allows you to slowly bring the lawn down to its seasonal height without violating the one-third rule. Once the initial rapid growth of spring slows, you can return to a standard weekly schedule.