Bermuda grass (Cynodon dactylon) is a warm-season grass often cultivated for its ability to withstand heat, drought, and heavy foot traffic. However, its aggressive growth habit means it is frequently encountered as a deeply invasive weed in cool-season lawns and garden beds. Its dense, mat-forming growth quickly overwhelms desirable turfgrasses and ornamental plants. Eliminating this grass is complicated, requiring persistence and a multi-faceted strategy for lasting control.
Why Bermuda Grass is Difficult to Remove
The tenacity of Bermuda grass stems from its specialized reproductive structure, which includes both above-ground stolons and below-ground rhizomes. Stolons are horizontal stems that spread rapidly across the soil surface, rooting down at their nodes to form new plants. Underneath the soil, thick, fleshy rhizomes serve as energy storage organs, making the plant highly resilient. Even if the visible grass blades are killed, the plant can regenerate completely from small, surviving segments of these rhizomes. The roots can also extend deep, sometimes reaching several feet, allowing the plant to access moisture and nutrients unavailable to many other turf species. This combination of runners, underground energy reserves, and deep roots is why physical removal or a single application of herbicide is rarely enough for complete eradication.
Non-Chemical Removal Techniques
For homeowners seeking an organic approach, non-chemical methods rely on blocking sunlight to starve the grass. Two effective techniques are soil solarization and sheet mulching, both requiring time and proper preparation.
Soil solarization uses clear plastic sheeting to trap solar heat, raising the soil temperature high enough to kill the grass and its rhizomes. To begin, mow the grass short and thoroughly saturate the soil with water to a depth of about 12 inches. Cover the wet soil with clear, UV-resistant plastic sheeting (typically 1.5 to 6 mil thick). The edges of the plastic must be completely buried in a trench to form an airtight seal, maximizing heat retention.
The plastic should remain in place for a minimum of six weeks during the hottest months of summer (June through August) to ensure lethal temperatures penetrate deep enough. While this method kills existing grass, it does not prevent new weeds from germinating once the plastic is removed.
Smothering, also known as sheet mulching, is a slower but effective technique that uses opaque layers to block all light. This process involves laying overlapping sheets of cardboard or several layers of newspaper directly over the mowed turf. The cardboard must be wetted thoroughly to aid decomposition and ensure it conforms to the ground. A thick layer of organic material, such as wood chips or compost, at least four inches deep, is then placed on top. This method requires six to ten months to fully kill the aggressive rhizomes, but it also enriches the soil as the organic materials break down.
Herbicide Application Strategies
Chemical control is often necessary for severe infestations or quick renovation, requiring careful timing and sequential treatments. The choice of herbicide depends on whether the goal is to kill the entire lawn or selectively remove the Bermuda grass from a desirable turf, such as a cool-season fescue lawn.
Non-selective herbicides, like glyphosate, kill nearly all vegetation they contact, including desirable turf. For total lawn renovation, apply the herbicide when the grass is actively growing and not stressed by drought. Applying it to active growth allows the chemical to be effectively translocated through the leaves down into the rhizomes.
A single application is insufficient because deep rhizomes often survive and sprout new growth. After the initial treatment, water the area to encourage surviving rhizomes to produce new shoots, which usually takes three to four weeks. A second, and possibly a third, application must then be made to target this new growth and exhaust the underground energy stores.
When Bermuda grass invades a cool-season lawn, selective herbicides must be used to target the warm-season grass without harming the existing turf. Herbicides containing active ingredients like fluazifop or clethodim are labeled for this purpose in certain cool-season grasses. These selective treatments are primarily suppressive and require a series of applications.
The timing of selective applications is critical, often starting in the early summer and repeating every three to four weeks according to the product label. Selective herbicides can cause temporary injury to the desirable turf, and multiple years of treatment may be needed for substantial reduction. Fall applications of non-selective herbicides are sometimes recommended as the grass is actively moving carbohydrates to the rhizomes, enhancing chemical movement to the storage organs.
Long-Term Prevention and Lawn Recovery
Achieving a Bermuda grass-free lawn requires establishing a strong, competing turf and persistent monitoring. After using a non-selective herbicide or smothering, the area must be prepared for new planting. If a non-selective chemical was used, follow any label-mandated waiting period before reseeding or laying sod to avoid damaging the new turf.
The most effective cultural practice for preventing re-establishment in cool-season turf is raising the mowing height. Bermuda grass is a sun-loving plant, but cool-season grasses like tall fescue can be maintained at 3.5 to 4 inches. This taller turf creates dense shade at the soil level, which suppresses Bermuda grass seedlings and weakens new shoots emerging from surviving rhizomes.
When reseeding, choose a competitive grass variety appropriate for the local climate to quickly fill in bare areas. A dense, healthy lawn naturally outcompetes new Bermuda grass seedlings. Prevention involves consistent monitoring of lawn edges, flower beds, and pavement cracks where stolons may creep in from adjacent areas.
Installing a deep, solid barrier, such as metal or plastic edging extending at least six inches into the soil, helps prevent new rhizomes from migrating into the treated area. Any new shoots that appear must be immediately spot-treated with a non-selective herbicide or carefully removed by hand, ensuring the entire rhizome is extracted to prevent re-sprouting.