St. Augustine grass (Stenotaphrum secundatum) is a popular warm-season turfgrass frequently used in the Southern United States. Valued for its coarse, broad leaf blades, this species tolerates heat, humidity, and moderate shade, making it a common choice for lawns along the Gulf Coast and in Florida. Homeowners seeking to repair bare areas must use a different approach than they would for cool-season varieties like fescue or rye.
The Reality of Seeding St. Augustine
St. Augustine grass is rarely grown commercially from seed, which explains why you will not find it sold in garden centers. Most popular cultivars, such as Floratam, are sterile and do not produce viable seeds, a characteristic that prevents unwanted volunteers. While some older or less common varieties, like Raleigh or Seville, can produce viable seeds, these seeds are difficult and costly to harvest because they are embedded in a corky material.
This grass is predominantly propagated vegetatively, meaning it is grown from pieces of the living plant rather than from seed. Its growth habit relies on stolons, which are above-ground runners that creep along the soil surface. This rapid lateral spread allows the grass to quickly fill in an area, whether it is an entire lawn established from sod or a small patch repaired with plugs. The lack of reliable seed means that attempting to fill in bare spots must rely on these vegetative methods.
Step-by-Step Guide for Seeding
For those who can source rare, viable seed, the process requires careful preparation. First, conduct a soil test to ensure the pH is slightly acidic to neutral, ideally between 6.0 and 7.5, and amend the soil as needed. Lightly scarify the bare soil surface with a rake to create excellent seed-to-soil contact, which is necessary for germination.
The optimal time for planting St. Augustine seed is in late spring or early summer, when daytime temperatures consistently reach 80 to 100 degrees Fahrenheit. Broadcast the seeds evenly over the prepared area, ensuring they are placed at a very shallow depth or lightly covered with a thin layer of topdressing, as the seeds require light to germinate. Following seeding, the area needs frequent, shallow watering to keep the top inch of soil consistently moist until germination occurs.
Using Plugs and Sprigs to Repair Bare Areas
The most effective solution for repairing bare patches is vegetative propagation using plugs or sprigs. Plugs are small, rooted sections of sod, typically two to four inches in diameter. Sprigs are stem runners without soil that contain nodes capable of rooting. Both methods utilize the stolon growth habit, allowing the grass to spread and fill the bare area.
To prepare the bare spot, remove any dead material and loosen the soil surface slightly to encourage new root growth. Plant the plugs into the soil, ensuring the top of the plug is level with the surrounding lawn surface to prevent scalping during mowing. Spacing plugs 6 to 12 inches apart in a staggered pattern encourages the fastest coverage.
If using sprigs, scatter them over the area and lightly cover them with soil, ensuring at least one node on each runner contacts the ground. Immediately after planting, an intense watering schedule is necessary to prevent the material from drying out. Keep the soil consistently moist for the first one to two weeks until the plugs or sprigs show signs of new growth.
Post-Establishment Maintenance
Once the new St. Augustine grass has established and begun sending out stolons, transition the watering schedule to promote deep root growth. Shift from frequent, shallow watering to deep, infrequent irrigation, aiming for about one inch of water per week, factoring in rainfall. This encourages roots to grow deeper, making the mature grass more resilient to drought and heat stress.
The mowing height should be maintained at a taller setting, typically between three and four inches, which is optimal for St. Augustine grass health and density. Taller blades provide more leaf surface area for photosynthesis and help the grass crowd out weed competition. Fertilization is necessary to fuel the lateral spread of the stolons. Begin with a balanced fertilizer, focusing on nitrogen, about two to three weeks after the grass greens up in the spring. Apply about one-half pound of actual nitrogen per 1,000 square feet in the late spring to encourage vigorous growth.