St. Augustinegrass is a warm-season turfgrass known for its aggressive, thick growth, creating a dense, carpet-like lawn. This grass spreads horizontally using above-ground stems called stolons (runners). Accelerating its spread requires specific cultural practices that support stolon growth. Optimizing the soil environment, applying the correct nutrients, and utilizing strategic maintenance techniques encourage St. Augustinegrass to cover ground quickly.
Optimizing the Soil Environment
The foundation for rapid stolon growth begins beneath the surface, where soil structure dictates root health and nutrient access. St. Augustinegrass thrives best in a slightly acidic to neutral soil pH, ideally ranging from 6.0 to 7.5. A soil test provides the precise pH and nutrient analysis needed to make informed amendments, such as applying lime or sulfur.
Soil compaction is a barrier to spreading because it restricts the movement of oxygen, water, and nutrients to the root system. Core aeration, which removes small plugs of soil, relieves this compression, especially in areas with heavy foot traffic. This process loosens the soil, allowing stolons to root more easily and laterally for quick coverage.
Good drainage is necessary, as St. Augustinegrass does not tolerate waterlogged conditions. Compacted soil contributes to poor drainage, but aeration creates channels for water to penetrate deeply. A healthy, loose soil structure ensures the grass can fully absorb water and nutrients, making fertilization more effective.
Strategic Fertilization for Runner Growth
Nitrogen (N) is the most influential nutrient for stimulating the vegetative growth and aggressive runner production needed for quick spreading. Nitrogen directly fuels above-ground growth, causing stolons to extend rapidly across bare areas. An annual application of 3 to 5 pounds of nitrogen per 1,000 square feet is recommended to support aggressive spreading.
To sustain this high-growth rate, use a fertilizer with high nitrogen and lower concentrations of phosphorus (P) and potassium (K). A common NPK ratio is 3-1-2 or 4-1-2, meaning the fertilizer has three to four times as much Nitrogen as Phosphorus. Using a slow-release nitrogen source is important because it provides a steady supply of the nutrient over several weeks, preventing the sudden surge of growth and potential burn associated with fast-release products.
Fertilizer application should coincide with the active growing season, starting a few weeks after the grass greens up in the spring. Applying 1 to 1.5 pounds of slow-release nitrogen per 1,000 square feet every 8 to 10 weeks throughout the summer maintains the consistent energy required for continuous stolon expansion. Secondary nutrients, such as Iron, can enhance the deep green color, indicating robust health.
Mowing and Watering Techniques
The way the lawn is cut directly impacts the grass’s ability to spread by maximizing photosynthetic capacity. St. Augustinegrass should be maintained at a tall height, ideally between 3 to 4 inches, to encourage quick coverage. Taller grass blades create more surface area for photosynthesis, allowing the plant to produce the energy reserves needed to push out new stolons.
Mowing too low (scalping) stresses the plant and exposes stolons to direct sunlight, halting their spread. Never remove more than one-third of the blade height at any single time, which may require frequent mowing during the peak growing season. Leaving the clippings on the lawn (grasscycling) recycles nutrients back into the soil, supporting the growth cycle.
The watering strategy must focus on encouraging deep root growth, which supports aggressive stolon production. Apply water deeply and infrequently, soaking the soil to a depth of about 6 inches, to promote a strong, drought-tolerant root system. Shallow watering encourages surface roots, leading to a weaker plant that cannot sustain rapid runner growth. Water only when the lawn shows signs of drought stress, such as a dull color or folded leaves.