St. Augustine grass (Stenotaphrum secundatum) is a popular warm-season turf choice for lawns across the Southern United States, valued for its dense, broad-leafed texture and vibrant color. This tropical species spreads aggressively through above-ground runners called stolons, quickly filling in bare areas to create a thick carpet. Successfully growing this grass requires attention to site preparation, a precise nutritional plan, and consistent physical care.
Preparing the Site and Planting
The successful establishment of St. Augustine grass begins with proper soil preparation, which ensures the roots can spread effectively and access nutrients. Before installation, perform a soil test to determine the existing pH level and nutrient composition. St. Augustine grass prefers a slightly acidic to neutral soil environment, with an ideal pH range between 6.0 and 7.5.
To improve soil structure and drainage, especially in compacted areas, consider aerating and leveling the site. Incorporating organic matter, such as compost, before planting will enhance fertility and water retention. Once the site is prepared, you can proceed with one of three primary installation methods.
The fastest way to establish a lawn is by laying sod, which provides immediate, uniform cover and significantly reduces weed competition. If cost is a greater concern than speed, planting small sections of grass called plugs is a more economical option. Plugs are spaced out and will spread via stolons to fill in the gaps, a process that can take a full growing season or more. The use of seed is not recommended because viable St. Augustine seed is often sterile or commercially difficult to source, making sod and plugs the most reliable choices for establishment.
Optimizing Nutritional Intake
St. Augustine grass is a heavy feeder, requiring a regular supply of nutrients, particularly nitrogen (N), to support its rapid growth. A fertilization program is best guided by a soil test. If a test is unavailable, a complete turf-grade fertilizer with a 3-1-2 or 4-1-2 nitrogen-phosphorus-potassium (N-P-K) ratio is often recommended. Using a slow-release nitrogen source is beneficial as it provides a steady supply of food, promoting consistent growth and reducing the risk of burning the turf.
The primary growing season requires the most attention. Apply 0.5 to 1 pound of actual nitrogen per 1,000 square feet typically in late spring or early summer after the grass has fully greened up. A second application should follow in mid-summer to maintain vigor during the hottest months. A final, light feeding in early fall is beneficial to encourage root growth and carbohydrate storage before winter dormancy.
Avoid heavy applications of nitrogen late in the season, approximately four to six weeks before the first historical frost. This timing can stimulate tender new growth that is highly susceptible to freeze damage. Over-fertilization should be avoided entirely, as excessive nitrogen can lead to thatch buildup and increase the grass’s susceptibility to diseases. The total annual nitrogen application should not exceed 4 pounds per 1,000 square feet.
Daily Care: Mowing and Hydration
The most frequent and impactful maintenance activities for St. Augustine grass are proper mowing and strategic hydration. A high mowing height directly influences the health and depth of the root system. St. Augustine grass should be maintained at a height between 3 and 4 inches, which encourages the roots to grow deeper into the soil.
This taller canopy also helps the grass shade its stolons and the soil surface, suppressing weed germination and aiding in moisture retention. When mowing, adhere to the “one-third rule,” meaning never remove more than one-third of the grass blade’s total height in a single cutting session. This practice prevents shocking the grass and ensures the plant has enough leaf surface area for photosynthesis.
For hydration, the goal is deep, infrequent watering rather than short, daily sprinkles. The lawn requires about 1 inch of water per week, delivered in one or two deep watering sessions. Deep watering encourages the roots to grow downward in search of moisture, making the grass more resilient to drought and heat stress. Water early in the morning to allow the foliage to dry completely before nightfall, minimizing the opportunity for fungal diseases to develop.
Diagnosing Common Growth Inhibitors
If a St. Augustine lawn fails to thrive despite proper care, the issue is often related to a specific pest, disease, or environmental stressor. One destructive insect pest is the southern chinch bug (Blissus insularis), which uses piercing-sucking mouthparts to extract sap from the grass stems. Damage first appears as irregular yellow patches that quickly turn brown, often concentrated in the hottest, driest areas of the lawn, such as along sidewalks or driveways.
Another common problem is Brown Patch fungus (Rhizoctonia solani), a fungal disease that affects the leaf sheaths at the base of the grass blade. The disease typically manifests as circular or semi-circular patches of yellowing or brown grass. Confirm its presence by tugging on the grass blades, which easily detach from the stolon due to rot at the base.
Environmental factors can also inhibit growth, with insufficient sunlight being a frequent cause. While St. Augustine grass has better shade tolerance than some other warm-season grasses, it still needs a minimum of six hours of direct sunlight per day to maintain density and health. Poor soil drainage is a major concern, as waterlogged conditions restrict oxygen flow to the roots, leading to a decline in growth and making the lawn vulnerable to root rot and fungal infections.