St. Augustine grass (Stenotaphrum secundatum) is a popular warm-season turf known for its attractive blue-green color and dense growth habit across the southern United States. While it thrives in heat and humidity, it is susceptible to various stressors that cause thinning and browning. Restoring a struggling St. Augustine lawn requires identifying the root problem and implementing a targeted revival strategy. This guide provides the necessary steps to return the turf to a lush condition.
Identifying the Cause of Decline
Accurately diagnosing the source of the turf’s distress is the initial step, as symptoms often overlap. Pests are a common cause of damage. Chinch bugs are particularly destructive in hot, sunny areas. They feed by sucking plant fluids, causing irregular patches of dry, straw-colored grass that look drought-stressed but fail to recover after watering. Mole crickets tunnel through the soil, disrupting the root system. Their presence is identified by spongy ground texture and visible tunnels near the soil surface.
Diseases often appear when the turf is stressed by improper watering or poor air circulation. Brown Patch (Rhizoctonia solani) presents as circular patches of yellowing grass with a darkened, smoke-ring border visible in the early morning. Grey Leaf Spot (Pyricularia grisea) occurs during high heat and humidity. It is characterized by small, elongated spots on the leaf blades with purple borders and grey centers.
Environmental and nutritional issues can mimic pest or disease activity, requiring careful observation. Drought stress causes blades to curl inward and take on a bluish-gray tint before turning brown. This indicates a lack of turgor pressure. Iron deficiency is a common nutritional issue, causing interveinal chlorosis. The tissue between the veins turns yellow while the veins themselves remain green.
Adjusting Foundational Maintenance
Once the cause of decline is identified, adjusting routine cultural practices strengthens the turf and promotes recovery. The height at which St. Augustine grass is cut significantly impacts its health, demanding a higher setting than many other turf varieties. Mowing the grass between three and four inches encourages deep rooting and allows the dense leaf canopy to shade the underlying stolons and soil.
Canopy shading helps conserve soil moisture and suppresses weed germination, creating a more resilient turf environment. Adhering to the “one-third rule” is also important; never remove more than one-third of the blade height in a single mowing session. Scalping the grass by cutting it too short places stress on the plant, weakening its ability to recover from damage.
Adjusting the watering schedule yields large benefits, particularly by focusing on deep, infrequent irrigation. Apply about one inch of water per week, delivered in one or two sessions. This encourages roots to grow downward, establishing drought tolerance. Light, daily watering keeps the surface layer wet, promoting shallow root growth and creating an ideal environment for fungal diseases.
St. Augustine grass is prone to developing a thick layer of thatch—a build-up of organic matter between the soil surface and the grass blades. When this layer becomes excessively thick, it impedes the movement of water, air, and nutrients into the root zone, leading to decline. Light mechanical aeration or vertical mowing helps break up this layer, improving the penetration of essential elements.
Specific Treatments for Revival
After correcting maintenance practices, targeted treatments are required to halt the progression of pests or diseases and stimulate renewed growth. If a pest infestation is confirmed, a specific insecticide application is necessary to stop the feeding damage immediately. Systemic products are often preferred because they are absorbed by the grass and provide sustained control. Apply the product according to label instructions, often targeting the thatch layer where pests reside, for effective control.
Confirmed fungal infections, such as Brown Patch or Grey Leaf Spot, require immediate treatment with an appropriate fungicide to prevent further spread. Selecting a broad-spectrum fungicide ensures the active ingredient targets the specific pathogen. These products suppress the fungal organism, allowing the grass plant to recover and push out new, healthy growth.
Nutrient correction plays a large role in revival, ensuring the lawn receives adequate nitrogen to fuel recovery and lateral growth. St. Augustine grass responds well to slow-release nitrogen formulations. These provide a steady supply of nutrients over several weeks without causing excessive growth flushes that can weaken the cell structure. Slow-release fertilizers minimize the risk of runoff and provide consistent feeding, which is beneficial for the turf’s stoloniferous growth habit. If iron deficiency (chlorosis) was identified, apply a chelated iron supplement to provide the necessary micronutrient for chlorophyll production and restore the deep green color without adding nitrogen.
For areas suffering severe decline that lack living stolons, aggressive physical intervention is needed, as St. Augustine grass does not establish reliably from seed. Homeowners should fill large barren patches by installing fresh sod plugs or transplanting healthy runners from an unaffected area. These small pieces contain the necessary growth points to spread laterally and quickly cover the damaged soil. This method ensures the area is quickly recolonized by the correct grass variety, restoring a uniform, dense turf stand.