St. Augustine grass is a popular choice for warm-season lawns due to its attractive blue-green color and thick, coarse-bladed texture. While new sod provides an instant lawn appearance, the turf remains highly vulnerable until its root system anchors firmly into the soil beneath. Successful establishment requires careful initial care, as the timing and execution of the first mowing are significant factors in preventing turf failure. Premature or improperly executed mowing can severely stress the nascent root structure, delaying the establishment phase and compromising the lawn’s long-term health.
Testing for Root Establishment
The moment for the initial cut is determined not by the calendar, but by the physical adhesion of the sod to the prepared soil below. New St. Augustine sod typically requires a waiting period of 10 to 14 days before root development is sufficient for mowing. During this phase, the turf’s rhizomes must extend root hairs down into the underlying soil bed, securing the sod and allowing it to absorb water and nutrients.
Homeowners can confirm this readiness using the “tug test.” Select a corner or seam of a sod piece and attempt to lift it gently. If the sod offers significant resistance, it indicates successful initial root establishment. If the sod lifts easily, the roots have not yet fully taken hold, and the lawn requires a few more days before it can withstand the stress of mowing.
Visual cues can also suggest readiness, such as the disappearance of the seams between the individual sod pieces as the grass begins to knit together. To ensure the soil is firm enough to support the weight of a mower without rutting, gradually reduce the frequency of watering in the two days leading up to the intended mowing day. A dry, firm surface is necessary to prevent the mower wheels from disturbing the newly formed root bonds.
Executing the Crucial First Mow
Once root establishment is confirmed, the first mow must be executed with precision to avoid damaging the vulnerable new turf. St. Augustine grass is a high-growing species, with a standard maintenance height between three and four inches. For the initial cut, set the mower blade to the highest possible setting to ensure minimal removal of leaf tissue. This high cut height promotes deep root growth by allowing the grass blades to maximize photosynthesis.
A fundamental rule for all mowing, especially the first cut on new sod, is the “one-third rule,” which states that no more than one-third of the grass blade’s total height should be removed in a single session. For instance, if the blades have reached four and a half inches, the mower should be set to remove a maximum of one and a half inches. Exceeding this limit can cause physiological shock, hindering the plant’s ability to recover and continue rooting.
The condition of the mower blade must be addressed before the first use. A dull blade tears the grass tissue, leaving a ragged cut that stresses the plant and creates an entry point for disease pathogens. A freshly sharpened blade ensures a clean, precise cut, allowing the grass to heal quickly and dedicate energy to continued root development. Using a lightweight walk-behind mower is also advisable, as heavy riding mowers can compact the soil and create deep ruts that damage the underlying roots.
Setting the Routine: Subsequent Mowing Frequency
Following the successful first cut, transition into a regular mowing schedule tailored to the establishment phase. The goal is to maintain a tall, healthy leaf canopy while continuing to adhere to the one-third rule. During periods of active growth, this often means moving to a weekly or bi-weekly mowing frequency, depending on the growth speed of the St. Augustine variety.
Maintaining the high cut height of three to four inches remains important throughout the first month of establishment. Cutting the grass shorter during this time can inhibit the necessary shade that the blades provide to the root zone, potentially stressing the developing turf. Consistent, high mowing encourages the dense, lateral growth habit characteristic of St. Augustine grass, helping the individual sod pieces fully integrate into a contiguous lawn.
As the lawn progresses through its establishment phase (typically the first four to six weeks), the maintenance routine will gradually shift. After the first few mows, the frequency of deep watering can be reduced to encourage the roots to seek moisture deeper in the soil profile. The first application of fertilizer should also be delayed until the sod is visually established and has been mowed multiple times, preventing chemical burn on the still-vulnerable new growth.