Carpet grass (Axonopus affinis) is a persistent, low-growing perennial grass often mistaken for desirable turf, especially in warm, humid climates. This warm-season grass forms dense, mat-like patches within lawns, making it a frustrating weed to control for homeowners seeking a uniform turf appearance. Its resilience and ability to thrive in poor conditions mean that eradication requires a multi-step, targeted approach. The following strategies provide actionable steps for identifying and completely removing this aggressive grass from your landscape.
Identifying Carpet Grass and Its Aggressive Nature
Carpet grass is identifiable by its pale green or yellowish-green color, which contrasts sharply with darker turf grasses like Bermuda or Zoysia. The leaves are wide, flat, and have distinct blunt or rounded tips, often growing only up to six inches long. A significant identifying feature is its tendency to produce tall, slender seed stalks with two to three spikelets that rapidly emerge.
The difficulty in eradicating this grass stems from its aggressive growth habit, primarily through above-ground runners called stolons. These stolons creep along the soil surface, rooting at the nodes to form new plants and quickly creating the dense “carpet” of growth. Carpet grass thrives in conditions that suppress other grasses, specifically acidic soils (pH below 6.0) and areas with poor drainage and high moisture. This preference allows it to outcompete and invade existing lawns.
Non-Chemical Removal Strategies
For small infestations or areas where chemical use is a concern, manual removal offers a precise, though labor-intensive, solution. Simple pulling of the grass blades is ineffective because the stolons and roots remain in the soil and quickly regrow. Complete manual removal requires digging out the entire plant, including all visible stolons and the entire root system, to prevent any remaining nodes from regenerating.
Smothering or solarization is a non-selective approach suitable for larger, isolated patches of carpet grass. This method involves covering the infested area with a thick layer of opaque material, such as black plastic sheeting, cardboard, or heavy organic mulch. Blocking all light starves the grass and superheats the soil, effectively killing the entire plant and its root structure. For this process to be successful, the covering must remain in place for a minimum of four to six weeks during the grass’s active growing season.
Selective Herbicide Treatments
Chemical control is often the most practical option for homeowners facing widespread carpet grass invasion within an otherwise healthy lawn. The treatment must be a selective post-emergent herbicide, meaning it targets the grassy weed without harming the surrounding desirable turf. Products containing the active ingredient metsulfuron-methyl or sulfentrazone are recommended for their effectiveness against this specific perennial grass. Celsius WG herbicide is another highly effective option, labeled to selectively control carpet grass in warm-season turf types like St. Augustine, Centipede, and Bermuda grass.
Application timing is crucial for maximizing the herbicide’s effect, as it must be applied when the carpet grass is actively growing, typically from late spring through summer. The herbicide should be applied to fully coat the leaves without runoff, allowing the plant to absorb the chemical for systemic killing. Due to the grass’s resilience, follow-up applications are necessary, usually repeated two to four weeks after the initial treatment, following the product’s specific label instructions. Always wear personal protective equipment and strictly adhere to the manufacturer’s dilution and application rates to ensure safety and prevent damage to the surrounding lawn.
Long-Term Prevention and Lawn Restoration
Eradicating the existing carpet grass is only half the battle; long-term prevention requires amending the soil conditions that allowed it to flourish. Carpet grass thrives in low-fertility, acidic soil, so a soil test is the first step to determine the exact pH level and nutrient deficiencies. Applying limestone (liming) will raise the soil pH toward the slightly acidic to neutral range of 6.2 to 7.0. This creates an environment unfavorable for carpet grass and more hospitable for healthy turf.
Improving soil drainage and aeration also directly counters the grass’s preference for moist conditions. Aerating the lawn pulls plugs of soil, improving air and water flow, which helps dry out the root zone and strengthens the roots of desirable grasses. Cultural practices, such as raising the mowing height to the upper recommended limit for your turf type, help shade the soil and suppress weed seed germination. Once the carpet grass is gone and the soil is amended, reseeding or sodding the bare patches with a competitive, desirable grass ensures the lawn is dense enough to crowd out future weed encroachment.