The first mow of a new lawn, whether established from seed or sod, requires careful timing and technique. This initial cutting is a step in encouraging the grass to develop a dense, healthy root system and a strong, lateral growth pattern. Rushing the process or using the wrong approach can shock the young turf, leading to patchy growth, root damage, and long-term weakness. Understanding the distinct readiness signals for different types of installations is necessary to ensure the lawn establishes itself successfully.
Determining the Right Time for Seeded Grass
The readiness of a lawn started from seed is determined by the height of the grass blades, not by a specific number of calendar days. You should wait until the new grass reaches a height of approximately three to four inches before considering the first cut. This height ensures the individual seedlings have developed enough leaf surface area for robust photosynthesis, which powers their root growth and overall establishment.
Cutting too early can shock the delicate, young plants, while allowing the grass to grow too tall can cause it to flop over, weakening the stems. When the grass reaches the target height, follow the “one-third rule,” which dictates that you should never remove more than the top one-third of the grass blade in any single mowing session.
If your grass is four inches tall, you should only cut off about one to one-and-a-half inches, leaving the blade height at a healthy three inches. This rule prevents the plant from losing too much of its food-producing capacity at once, minimizing stress on the developing root system.
Before you begin mowing, perform a gentle “tug test” on the seedlings. If the plants resist the light upward pull and remain anchored in the soil, they are sufficiently rooted to withstand the suction and mechanical action of the mower.
The First Cut for Sod and Sprig Installations
Unlike a seeded lawn, the timing for the first cut of newly laid sod or sprigs depends entirely on root establishment, not blade height. Sod, which is essentially pre-grown turf, needs time for the roots to penetrate the underlying soil and securely anchor the mat in place. This process typically takes about two to three weeks after installation, but the physical test is the only reliable indicator of readiness.
To check if sod is ready, gently lift an edge or corner of a piece of turf. If the sod resists the pull and feels firmly connected to the soil beneath it, the roots have established enough to handle the stress of mowing. If the turf easily lifts or peels back, you must wait longer, as mowing too soon will tear the sod, disrupt the root-to-soil connection, and cause sections to dehydrate and die.
Installations using sprigs, which are pieces of grass stems and roots, require a longer wait. Sprigs need time for their runners to spread and anchor themselves firmly into the soil before any mechanical stress is applied. The first cut for a sprig-based lawn usually occurs between three to six weeks, or when the runners are visibly established and the grass blades have reached the appropriate height for a light trim.
Essential Mowing Technique and Equipment Setup
The first mow demands careful technique and attention to equipment setup to avoid damaging the vulnerable new turf. To ensure a clean cut that minimizes stress on the grass, you must use a mower with a freshly sharpened blade. A dull blade will tear or shred the grass tips, creating ragged, open wounds that turn white or brown and invite disease.
Set your mower deck to its highest setting before starting, as this helps you adhere to the one-third rule while avoiding accidental scalping of any high spots in the new ground. A lightweight push mower is preferable over a heavy riding mower for the initial cuts, since the weight of heavier equipment can compact the soft, newly laid soil, which is detrimental to root growth.
When you mow, vary your direction from the pattern of the sod or the direction of the seeding application. This practice prevents the mower’s suction from pulling up loose seedlings or disturbing the seams of the sod pieces.
If the clippings are short and light, you can leave them on the lawn to recycle nutrients, but if the cut was heavy, bag the clippings to prevent them from smothering the young grass or creating a layer of suffocating thatch.