Establishing a new lawn, whether from seed or sod, requires careful timing for the first mowing. Cutting the grass at the correct time and with the right technique encourages robust root growth and helps the turf transition into a resilient, established lawn. Misjudging this initial cut can severely stress the young grass, potentially leading to disease, thinning, and delayed establishment. The timing for this first trim depends entirely on the method used to start the lawn.
Timing for Newly Seeded Lawns
The primary factor for determining when to mow a newly seeded lawn is the height of the grass blades, not the date of planting. Most grass species need to reach a height of at least three to four inches before the first cut can safely occur. Waiting for this height ensures the young seedlings have developed enough leaf surface to conduct sufficient photosynthesis, which fuels the rapid growth of the root system.
Before mowing, confirm the seedlings have anchored securely to the soil. A simple test involves gently tugging on a few blades of grass. If the blades resist the pull and do not easily lift out, the roots are established enough to handle the mechanical stress of mowing. Mowing too early risks uprooting the immature plants, which creates bare patches and stunts development.
The goal of the first mow is to remove only the tips of the tallest blades, which encourages the plant to begin lateral growth and promotes a denser turf. For the initial cut, it is recommended to wait until the majority of the grass reaches about one-third higher than the desired maintenance height. This allows a clean cut that follows the “one-third rule” while still providing the seedlings an extended period for root establishment.
Timing for Newly Sodded Lawns
Unlike seeded lawns, the readiness of newly laid sod for its first cut is determined by root integration and soil stability, as the grass blades are already mature. The general timeline for the first mow is typically around 10 to 14 days after installation, but this can vary depending on the growing conditions. The most reliable method for checking readiness is a physical inspection of the root system.
Perform a “tug test” by gently attempting to lift a corner or edge of a sod roll. If the sod lifts easily, the roots have not yet attached to the underlying soil, and mowing should be delayed. When the sod resists the lift and feels firmly anchored, it indicates that new, fine white roots have integrated into the prepared soil.
A secondary check is the firmness of the soil itself. New sod requires frequent watering, which often leaves the soil soft. Mowing on soft ground can cause the mower wheels to leave deep ruts or compact the soil, hindering root growth. Cutting back on watering the day before the planned mow allows the soil to firm up, providing a stable base.
Essential Mowing Technique
Once the new grass is ready, the technique used for the first cut is important to prevent unnecessary stress. The rule for mowing any new lawn is the “one-third rule,” which dictates that no more than one-third of the grass blade’s total height should be removed in a single session. This practice minimizes shock, ensuring enough leaf surface remains for energy production through photosynthesis.
Before starting, the mower blades must be sharpened to a keen edge; dull blades tear the grass blades rather than slicing them cleanly. A torn blade tip results in a ragged, open wound that turns brown and makes the plant more susceptible to disease and moisture loss. The mower deck should also be set to the highest possible setting for the first few cuts, aiming for a final height typically between three and four inches.
Mowing should only occur when the grass and soil are completely dry. Mowing wet grass results in an uneven cut and can cause clippings to clump, which smothers the young turf. Using a lightweight mower for the initial cuts helps reduce soil compaction. Changing the mowing pattern with each subsequent cut promotes upright, dense growth.