Carpet Grass is a persistent perennial weed that frustrates warm-season turf owners. This aggressive species forms dense, low-growing mats that compete vigorously with desirable lawn grasses for resources. Effective control requires a precise strategy combining correct identification, optimal timing, and the careful selection of a selective herbicide. The goal is to eliminate the invading grass without damaging the surrounding turfgrass.
Confirming the Weed and Optimal Treatment Timing
Carpet Grass is easily recognized by its creeping growth habit, extending via above-ground stems called stolons that root at the nodes to form new plants. The leaf blades are often shiny and light green. Its inflorescence typically features two slender, finger-like flower stalks that diverge from the top of the stem, resembling a “T.”
Post-emergent treatments are most effective when the weed is actively growing, generally from late spring through mid-summer. Actively growing plants efficiently absorb and transport the herbicide throughout their system, including the extensive stolons.
Applying herbicides during periods of dormancy, drought, or extreme heat is not recommended. When temperatures consistently exceed 90°F, plant metabolism slows down, reducing chemical uptake and increasing the risk of injury to the desirable turf. Application should occur on a calm day when the grass is well-watered but not saturated to maximize absorption and minimize drift.
Targeted Selective Herbicide Options
Monosodium Methyl Arsonate (MSMA) was historically reliable for controlling Carpet Grass, especially in Bermuda and Zoysia lawns. However, the Environmental Protection Agency (EPA) has largely phased out MSMA for residential use, restricting it primarily to commercial sites like golf courses and sod farms.
Homeowners must rely on newer chemistries safe for common warm-season grasses like St. Augustine, Centipede, Bermuda, and Zoysia. Combination products containing Sulfentrazone, often mixed with active ingredients like thiencarbazone-methyl and dicamba, effectively control Carpet Grass and other difficult grassy weeds. Sulfentrazone works by inhibiting a plant enzyme, causing rapid cell membrane disruption in susceptible weeds.
Another viable option is metsulfuron-methyl, a sulfonylurea herbicide generally safe for many warm-season turf varieties that suppresses Carpet Grass. Selective herbicides like Quinclorac, while excellent for crabgrass, can significantly damage St. Augustine and Centipede grass, making them unsuitable choices. Always confirm the product label specifically lists the target weed and is rated as safe for the type of turfgrass in the lawn.
Safe and Effective Application Methods
Proper mixing and calibration are essential. Always follow the manufacturer’s directions for mixing ratios exactly, as over-application can severely injure the desirable lawn turf. Many herbicides require a non-ionic surfactant, an additive that helps the chemical stick to the leaf surface, improving absorption.
Sprayer calibration ensures the correct amount of product is applied evenly, preventing missed spots or chemical burn. Use a pump sprayer dedicated to herbicides to avoid cross-contamination. Personal protective equipment (PPE), including chemical-resistant gloves, protective eyewear, and long sleeves, should be worn during mixing and application to prevent contact.
After application, allow the herbicide to dry completely, typically for at least 24 hours, before irrigation or rainfall. Avoid mowing the lawn for three to four days both before and after spraying to allow maximum leaf surface area for absorption and chemical translocation. Since Carpet Grass is a perennial, complete eradication often requires sequential treatments, with a second application typically needed two to four weeks after the first to target surviving weeds.