St. Augustine grass (Stenotaphrum secundatum) is a popular warm-season turf widely utilized across the Southeastern United States. Characterized by its distinct coarse texture and dense, carpet-like growth habit, it provides excellent ground coverage and a lush appearance. However, St. Augustine grass has relatively high maintenance requirements to thrive. Understanding the specific cultural practices this turf demands is essential for achieving a healthy, vigorous lawn.
Establishing Proper Mowing and Watering Habits
Proper physical maintenance begins with the height and frequency of cutting. St. Augustine grass performs best when mowed at a finished height between three and four inches. This taller height encourages deeper, more robust root systems, significantly improving drought tolerance. The increased leaf surface area also helps shade the soil, reducing water evaporation and suppressing weed seed germination.
Adhere to the “one-third rule,” which dictates that no more than one-third of the grass blade height should be removed during any single mowing session. This prevents excessive stress and reduces susceptibility to disease. During the active growing season, mowing may be required every five to seven days to maintain the desired height.
Effective irrigation focuses on deep and infrequent watering. Apply approximately one inch of water per week, distributed over one or two separate sessions. This method trains the roots to grow downward seeking moisture, making the turf more resilient to heat stress.
Watering should ideally take place in the early morning hours, typically between 4:00 AM and 10:00 AM. Applying water during this window allows the foliage to dry completely before nightfall, minimizing the prolonged leaf wetness necessary for fungal diseases to proliferate.
Implementing a Seasonal Fertilization Strategy
Nutrient management must be carefully timed to match the plant’s active growth cycles. The initial fertilizer application should occur in late spring, after the grass has fully emerged from dormancy and is exhibiting vigorous growth. Applying fertilizer too early can prematurely stimulate top growth before the root system is adequately developed, potentially leading to weakened turf.
A second application is beneficial in mid-to-late summer to sustain growth and color. Cease all nitrogen-heavy fertilization by early fall, about six to eight weeks before the first expected frost. Late-season nitrogen encourages tender new growth that is easily damaged by cold temperatures, reducing the lawn’s hardiness heading into winter.
St. Augustine grass requires significant nitrogen (N) for its dense, vibrant green appearance. However, over-fertilization can lead to excessive thatch buildup and increased disease susceptibility. Soil testing is recommended to accurately determine the specific NPK (Nitrogen-Phosphorus-Potassium) ratio required.
A common issue is chlorosis, or yellowing, often caused by an iron deficiency, particularly in alkaline soil. Addressing this requires the application of chelated iron supplements. These supplements restore the deep green color without adding unnecessary nitrogen.
Identifying and Treating Common Lawn Afflictions
Maintaining a healthy St. Augustine lawn requires proactive monitoring for common biological threats, including insects, diseases, and weeds. The southern chinch bug is the most destructive insect pest and requires immediate attention. Damage appears as irregular, spreading patches of yellowing, dead grass, particularly in hot, dry areas like along sidewalks or driveways.
These tiny insects feed on the sap at the base of the grass blades, injecting a toxin that causes the tissue to die. The damage mimics severe drought stress but will not recover with additional watering. Confirmation requires parting the grass near the damaged area to observe the small black insects with white diamond-shaped markings. Treatment involves the targeted application of specific insecticides, often requiring a follow-up application to break the pest’s reproductive cycle.
A significant fungal problem is Brown Patch, caused by Rhizoctonia solani. This disease manifests as circular or semi-circular patches of dark, water-soaked, or yellowing grass, ranging from a few inches to several feet in diameter. Brown Patch is prevalent in cooler, overly wet conditions, often during spring or fall when humidity is high.
Cultural practices like ensuring good air circulation and adhering to early morning watering are the first line of defense. If the disease is severe, a lawn-specific fungicide may be necessary to halt the spread. While regular dethatching is not recommended, excessive thatch or severe soil compaction may necessitate professional aeration to improve drainage and reduce disease risk.
Effective weed management requires a two-pronged approach: pre-emergent and post-emergent strategies. Pre-emergent herbicides are applied in late winter or early spring, before soil temperatures allow weed seeds to germinate. This creates a chemical barrier preventing the emergence of annual grassy weeds, like crabgrass, and some broadleaf weeds.
For existing weeds, a post-emergent herbicide is required, but selecting the correct product is paramount. St. Augustine grass is highly sensitive to many common turf chemicals. Certain herbicides, especially those containing 2,4-D, can severely injure or kill the grass. Always confirm the product label explicitly states suitability for use on Stenotaphrum secundatum to avoid damaging the turf.