Bermuda grass is a warm-season grass that presents a significant challenge when it invades cool-season turf areas like those comprised of Fescue or Kentucky Bluegrass. Its rapid, dense growth and ability to withstand high heat and drought conditions make it a successful turf grass in the South, but a highly aggressive and persistent weed elsewhere. Eliminating this invasive grass requires an understanding of its unique biology and the adoption of a strategic, multi-step approach.
Understanding the Biology of Bermuda Grass
The difficulty in eradicating Bermuda grass lies in its extensive, dual root system, which allows it to store immense reserves of energy and rapidly colonize new areas. The plant spreads both above and below the soil line using specialized horizontal stems known as stolons and rhizomes. Stolons are above-ground runners that creep along the soil surface, rooting at their nodes to form new plants.
Rhizomes are the more problematic component, consisting of sharp, underground stems that can penetrate the soil to depths of six inches or more. These rhizomes function as survival mechanisms, storing the carbohydrates that fuel regrowth even after the visible green shoots are destroyed. Consequently, simple methods like hand-pulling or routine mowing fail to kill the plant, as the underground network of rhizomes remains intact, ready to sprout new growth.
Non-Chemical Eradication Techniques
For those committed to avoiding herbicides, the most effective non-chemical methods involve aggressively depriving the grass of sunlight and heat over an extended period. Solarization utilizes the sun’s energy to “cook” the grass and its underground structures, making it a viable option during the hottest months of the year. To solarize successfully, the Bermuda grass should be mowed as low as possible, and the area should be thoroughly watered to increase the soil’s heat conductivity.
The prepared area is then covered with clear, 4- to 6-mil plastic sheeting, which must extend at least two feet beyond the visible edge of the infestation to capture the creeping stolons. This clear plastic creates a greenhouse effect, raising the soil temperature high enough—often exceeding 140°F—to kill the plant’s rhizomes and seeds. The plastic must remain in place and secured for a minimum of four to six weeks during peak sun exposure for the heat to penetrate deeply enough to be effective.
An alternative method is smothering, which blocks sunlight entirely, forcing the plant to exhaust its energy reserves. This technique involves covering the affected area with an opaque material, typically flattened cardboard or a thick layer of newspaper, followed by several inches of organic mulch or compost. The layered materials must overlap significantly to prevent the grass from finding gaps and should remain undisturbed for a minimum of four to six months. While manual removal through digging is possible, every piece of rhizome must be removed, as fragments as small as half an inch can regenerate a new plant.
Selective Chemical Control in Existing Lawns
When Bermuda grass has begun to invade a desirable cool-season lawn, selective herbicides offer a way to target the weed without destroying the entire turf stand. This approach relies on specific active ingredients that are tolerated by the cool-season grasses but toxic to the warm-season Bermuda grass. Selective control is a process of suppression and weakening, not a single-application kill, requiring patience and precise timing.
The most common active ingredients used for this purpose include Fenoxaprop-p-ethyl, Sethoxydim, and Fluazifop, which are grass-selective herbicides known as “grassy weed killers.” These chemicals inhibit key enzymes in the Bermuda grass, disrupting its growth and metabolism while leaving the established cool-season turf largely unharmed. The application must be timed for when the Bermuda grass is actively growing and translocating nutrients—typically in late summer or early fall—but before it enters dormancy.
A successful selective treatment requires multiple applications, usually spaced two to four weeks apart, to progressively deplete the rhizome’s energy stores. Following the label instructions exactly is paramount, as exceeding the recommended rate can damage the desirable turf, while under-applying will not effectively kill the tenacious Bermuda grass. Often, a non-ionic surfactant or methylated seed oil is necessary to help the herbicide penetrate the waxy leaf surface of the grass.
Complete Lawn Renovation Using Non-Selective Methods
For lawns that are heavily contaminated, or where Bermuda grass comprises more than 10 to 15 percent of the turf area, the most reliable strategy is a complete lawn renovation. This method involves using a non-selective herbicide to kill all vegetation in the area and starting fresh. The herbicide of choice is Glyphosate, a systemic product absorbed by the leaves and transported down to the rhizomes.
The process demands a minimum of two applications to ensure the deeply embedded rhizomes are fully eradicated. The first application should occur when the Bermuda grass is actively growing in the summer heat, followed by irrigation to encourage any surviving rhizomes to sprout. After waiting ten to fourteen days, a second application must be made to kill the newly emerged shoots and any remaining root structures.
Once the entire area is completely dead, the debris must be removed, typically through aggressive dethatching or verticutting, to prepare a clean seedbed. Tilling the soil is generally discouraged, as it can bring viable rhizome fragments and dormant weed seeds to the surface. For cool-season lawns, the renovation should be timed so that the final application and seedbed preparation are completed just before the optimal fall seeding window. This allows the new grass to establish strong roots before the onset of winter and the following summer’s heat.