St. Augustine grass is a popular warm-season turf in southern climates, known for its dense, carpet-like growth. This grass variety spreads primarily through above-ground runners, called stolons, creating a thick turf. Bare spots are a common maintenance challenge that disrupt the lawn’s uniformity. These damaged patches invite weeds and can lead to soil erosion and compaction. Repairing these areas requires a targeted approach, beginning with diagnosing the underlying issue.
Identifying the Root Cause of Bare Spots
The first step in any successful repair is to determine precisely why the St. Augustine grass failed in that specific area, as simply replanting will not resolve an ongoing problem. One common culprit is the southern chinch bug, a tiny insect that feeds by sucking the sap from grass blades, injecting a toxic saliva in the process. Chinch bug damage typically appears as expanding, irregular patches of yellowish-brown grass, often most severe during hot, dry weather.
Fungal diseases, such as Brown Patch, present a different pattern, characterized by circular or semi-circular areas of yellowing grass. You can test for Brown Patch by gently tugging on a leaf blade within the affected zone; if it easily slips away from the runner, the fungus has likely rotted the stem base. Bare areas can also be caused by environmental factors, including excessive shade. St. Augustine grass requires a decent amount of sunlight, despite being more shade-tolerant than some other warm-season grasses. Another frequent cause is soil compaction, which prevents proper root growth, or heavy foot traffic that physically wears down the surface runners.
Site Preparation Before Planting
After the root cause is identified and treated, the bare area must be prepared to accept new grass material. First, remove all dead grass and debris using a hard-tined rake or dethatching tool. This exposes the soil surface and ensures new growth does not compete with decaying matter.
Next, address the soil structure, especially if compaction was an issue, by lightly loosening the top few inches. Use a garden trowel for small spots, or a core aerator for larger areas, to improve drainage and aeration. Amend the existing soil by adding a thin layer of compost or a mixture of topsoil and sand to enrich the area and maintain moisture. Ensure the repaired area is level with the surrounding lawn to prevent water pooling or uneven mowing.
Step-by-Step St. Augustine Repair Techniques
Since St. Augustine grass rarely produces viable seed, bare spots must be repaired using vegetative methods: plugs, sod pieces, or runners.
Using Plugs
For small to medium-sized bare spots, planting grass plugs is a simple and effective technique. Use a specialized plug tool or a small auger bit to create holes roughly the size of the plug, spaced approximately 12 to 18 inches apart. Insert the plugs into the holes, ensuring the crown is flush with the soil surface. Gently tamp the soil around them to eliminate air pockets.
Using Runners
Another cost-effective method involves using runners, or stolons, harvested from a healthy, dense section of the existing lawn. These runners can be cut into short segments and pinned down onto the bare soil to encourage rooting. This method takes longer to achieve full coverage.
Using Sod
For larger areas requiring immediate, seamless coverage, installing fresh sod is the fastest solution. Cut the sod piece to fit the exact dimensions of the bare spot. Ensure the edges make firm contact with the surrounding healthy turf. Press the sod piece firmly into the prepared soil to ensure good root-to-soil contact, which is crucial for successful establishment.
Establishing and Blending the New Grass
The period immediately following planting is crucial for the new grass to establish a robust root system and blend into the existing turf. During the first two to three weeks, the newly planted plugs, runners, or sod pieces require frequent, shallow watering to prevent the roots from drying out. Water two to three times daily, applying just enough water to keep the top few inches of soil consistently moist.
After this initial establishment phase, gradually reduce the watering frequency to encourage the grass to develop deeper roots, transitioning to a schedule of deep, less frequent irrigation. An application of a starter fertilizer, which typically contains a higher proportion of phosphorus, can be beneficial shortly after planting to stimulate root growth. Avoid using general-purpose, high-nitrogen fertilizers at this stage, as they promote top growth at the expense of root development.
Do not mow the repaired area until the new grass has firmly rooted, which usually takes about four to six weeks, or until the stolons have begun to spread noticeably. When you do mow, set the mower to the highest recommended height for St. Augustine grass, which is typically between three and four inches. Maintaining a higher cut protects the new, vulnerable growth and encourages the runners to spread horizontally, ultimately creating a dense, uniform, and completely blended lawn surface.