St. Augustine grass is a highly favored turfgrass across Texas due to its broad leaf blades, deep emerald-green color, and ability to thrive in the state’s hot, humid climate. This warm-season variety is particularly valued for its superior shade tolerance, making it ideal for residential areas. Successfully establishing a new St. Augustine lawn from sod requires a strategy where the timing and composition of fertilizer are tailored to the grass’s immediate needs. The initial weeks focus on intense root development, meaning delaying nutrient application is crucial.
Establishing the Root System Before Feeding
Before any nutrients are applied, the new sod must focus on anchoring itself into the underlying soil. Immediately after installation, the sod requires intensive watering to prevent the delicate root system from drying out, a significant risk in the Texas heat. For the first seven to ten days, keep the soil underneath the sod consistently moist, requiring multiple short, deep watering sessions daily to saturate the top few inches.
After the initial week, gradually reduce the watering frequency. This shifts the focus from keeping the surface wet to encouraging the roots to grow deeper in search of moisture. This reduction in surface moisture also firms up the soil before the first mowing. The first cut should occur around 14 days post-installation, once a gentle tug confirms the sod has begun to anchor itself with new white roots.
When mowing for the first time, set the mower blade to its highest setting, typically between 2.5 and 3.5 inches for St. Augustine grass. Never remove more than one-third of the leaf blade during any single session. Waiting until this two-week establishment period is complete and the first mowing has occurred ensures the root system is ready to absorb and utilize fertilizer without damage.
The Critical First Application: Timing and Formula
The optimal window for the first fertilizer application is typically two to four weeks after the new sod has been laid, once there is clear evidence of root establishment. Applying fertilizer too early, especially a high-nitrogen product, can stimulate excessive leaf growth at the expense of root development, or chemically burn the fragile new roots. The goal of this initial feeding is to support the horizontal spread of stolons and the vertical growth of roots, not to promote a sudden flush of green top growth.
For this initial stage, a starter fertilizer is required, characterized by a high phosphorus (P) content, the middle number in the NPK ratio. Phosphorus is crucial for energy transfer and root cell division, making it the most important nutrient for establishing new sod. Recommended starter NPK ratios are typically balanced, such as 8-8-8 or 15-15-15, ensuring the grass receives the necessary phosphorus and potassium for root vigor.
Apply the fertilizer evenly using a broadcast spreader, followed immediately by a thorough watering. This moves the nutrients down to the root zone and prevents burning the leaf tissue. Avoid using any “weed-and-feed” products during this establishment phase. The herbicides in these combined products are too harsh for immature sod and can severely damage the young grass.
Developing a Seasonal Fertilization Schedule
Once the new sod is fully rooted and has been mowed a few times, the feeding program transitions from establishment to a seasonal maintenance schedule specific to the Texas growing season. The next feeding should occur approximately six to eight weeks after the initial starter fertilizer application. Subsequent feedings will shift away from the phosphorus-heavy starter formula toward a nitrogen-dominant, slow-release product to sustain healthy top growth.
For mature St. Augustine growth in Texas, a fertilizer with a 3-1-2 or 4-1-2 NPK ratio is recommended, such as 15-5-10 or 21-7-14. St. Augustine grass requires between two and four pounds of nitrogen per 1,000 square feet annually. Individual applications should deliver 0.5 to 1 pound of nitrogen every eight to ten weeks during the active growing season. The spring application should be timed after the grass has fully emerged from winter dormancy and the risk of a late frost has passed, usually between March and May.
The intense Texas summer heat requires a careful approach to fertilization, as applying high-nitrogen fertilizer to grass stressed by extreme temperatures can cause chemical burns. Subsequent feedings should continue through late summer to fuel growth. However, all fertilization should cease four to six weeks before the first expected frost to prevent stimulating tender new growth vulnerable to winter cold. Since many Texas soils are naturally alkaline, an application of a liquid or granular iron supplement is often beneficial between fertilizer applications to maintain a deep green color.