The installation of new sod provides the immediate satisfaction of a lush, green lawn, but the first few weeks following placement are a delicate period for the turf. Beneath the visible grass blades, a biological process is occurring that determines the long-term success of the lawn. Rushing the first mowing before this process is complete can severely damage the young turf, leading to an uneven, unhealthy, or patchy surface. Allowing the new grass to fully anchor itself to the ground is essential during this initial phase.
The Goal of the Waiting Period
The objective of postponing the first cut is to allow the sod’s root system to establish a strong connection with the underlying soil. This process, often referred to as “knitting,” involves the growth of new, fine root hairs from the sod mat down into the prepared soil bed below. The sod is a harvested turf product and must regrow the roots that were severed during its transport.
Shallow roots typically begin to emerge and penetrate the native soil within 10 to 14 days following installation. This initial rooting secures the sod pieces to the ground and allows them to begin drawing water and nutrients from the earth. While 10 to 14 days is often cited, this timeline can vary based on factors like grass type, climate conditions, and the time of year. Rooting may be slower in cooler weather, for example.
During this waiting period, a controlled watering schedule encourages the roots to grow deeply for long-term health and drought resistance. The goal is to keep the sod and the top layer of soil moist but not saturated, prompting the roots to search downward for water. Cutting the grass too soon risks physically dislodging these newly forming roots, which can cause stress and potentially kill the grass.
Confirming Sod Readiness
The calendar provides only a rough estimate; the physical readiness of the turf, rather than a specific number of days, should dictate the timing of the first mow. The most practical and reliable test a homeowner can perform is the gentle “Tug Test.” This test directly assesses the progress of the root knitting process.
To perform the test, select a corner or edge of a sod piece and attempt to lift it gently. If the sod lifts easily or separates readily from the soil, the roots have not sufficiently anchored and more time is needed. If the piece resists the pull and feels firmly secured, it indicates that the new roots have successfully grown into the soil below.
It is important to perform this check in several different areas of the lawn to ensure consistent rooting across the entire installation. Waiting until the sod is firmly rooted protects the turf from being torn up or shifted by the force of the mower blades and the weight of the equipment. Once the sod passes this physical resistance test, the lawn is structurally ready to support the mowing process.
Specifics of the Initial Mowing
Before the first cut, let the soil dry out slightly by withholding water for about 24 hours. This allows the ground to firm up, ensuring the mower’s weight does not create ruts, tear the sod, or compact the soft soil. Using a walk-behind mower is preferable to a heavier riding mower for the initial cuts to minimize soil compaction.
The mower blades must be sharpened immediately before use to ensure a clean cut. Dull blades will tear the grass, stressing the new plants and leaving open wounds susceptible to disease. The height of the mower deck should be set to the highest possible setting for the first cut, typically resulting in a grass height of 2.5 to 3 inches after trimming.
It is necessary to follow the “one-third rule,” which dictates that no more than one-third of the grass blade’s height should be removed during any single mowing session. For example, if the grass has grown to 4.5 inches, the finished cut height should not be lower than 3 inches. This practice minimizes shock to the grass plant, preserving the leaf surface necessary for photosynthesis to support continued root growth.
The first few passes should be executed slowly and deliberately. Mowing diagonally to the direction the sod was laid can help prevent accidental shifting of the turf strips. If the resulting clippings are light and do not form heavy clumps, they should be left on the lawn to return moisture and nutrients to the new sod.