Bermuda grass, or Cynodon dactylon, is a durable turfgrass, but its aggressive spreading habit makes it a persistent weed when it invades flower beds. Removing this grass without harming surrounding ornamental plants presents a unique challenge. This process requires a targeted approach that addresses the plant’s unique biology, combining careful manual removal with selective chemical or non-chemical treatments. Success depends on eliminating the entire root system while protecting the established garden environment.
Understanding Bermuda Grass Aggression
The tenacity of Bermuda grass stems from its dual root system, allowing it to spread both above and below the soil surface. Above ground, the plant uses horizontal stems called stolons, which creep along the soil and root down at the nodes to form new plants. This visible network is relatively easy to sever.
The true source of its resilience lies beneath the surface in its rhizomes, which are underground stems often mistaken for roots. These rhizomes serve as storage organs for carbohydrates, allowing the grass to survive drought, cold, and repeated mowing. Rhizomes can be found up to six inches deep, and even small fragments left behind can quickly sprout into a new plant. Successful eradication requires eliminating both the above-ground stolons and the entire network of underground rhizomes.
Non-Chemical Eradication Strategies
For flower beds with established, desirable plants, manual and non-chemical methods offer the safest way to remove Bermuda grass without risking damage to ornamentals. Hand digging is the most immediate but labor-intensive strategy, requiring careful attention to detail. Start by watering the area to loosen the soil, making it easier to pull the entire rhizome system without breaking it into propagation-ready fragments.
Using a garden fork or trowel, gently lift the invaded soil, tracing the rhizomes back to their source. After removing the visible grass and runners, sift the soil through your fingers to find and remove every tiny piece of rhizome, since even a small fragment can regenerate. This method is best for small, localized patches.
For larger, more concentrated areas, focused smothering, also known as sheet mulching, can be effective. This technique involves covering the Bermuda grass with a light-blocking material, such as layered cardboard or black plastic sheeting, to deprive the plant of sunlight. The material must be carefully tucked around existing flowers and secured to the ground, overlapping the edges by at least six inches to prevent the grass from finding a path to light.
While complete solarization using clear plastic can generate high heat to kill the grass, black plastic or thick cardboard is safer to use around established plants, though it requires a longer duration. Another option is the targeted application of horticultural vinegar, which contains a higher concentration of acetic acid (20% or more) than household vinegar. This substance rapidly desiccates the leaves on contact, but it is non-selective and will harm any plant it touches, requiring extreme caution and shield use to protect nearby flowers.
Targeted Chemical Solutions
When non-chemical methods are impractical or fail to control a severe infestation, selective chemical solutions provide a targeted approach. The most effective options are grass-specific, post-emergent herbicides, which are designed to kill monocots (grasses) while sparing dicots (broadleaf flowers and shrubs). Products containing the active ingredients Sethoxydim or Fluazifop-P-butyl are commonly available and work by inhibiting an enzyme found only in grasses.
Because these chemicals are selective, they can be sprayed directly over many broadleaf ornamentals, but always confirm plant tolerance by reading the product label carefully. For use within a dense flower bed, a more precise method is targeted application. Apply the herbicide directly to the Bermuda grass blades using a foam brush, sponge, or specialized wick instead of spraying.
This localized application minimizes the risk of spray drift onto sensitive plants and helps to ensure the chemical is absorbed by the target grass. For the herbicide to be effective, Bermuda grass must be actively growing, not drought-stressed, and have sufficient leaf surface area for absorption. Follow-up applications on new growth are almost always necessary for complete control, as the deep rhizomes make the grass highly resilient.
Long-Term Prevention Measures
After the initial eradication effort, preventing the re-entry of Bermuda grass is paramount to maintaining a clear flower bed. Physical barriers are the most effective long-term defense against invasion from adjacent lawns or turf areas. Installing a rigid edging made of metal, plastic, or concrete that extends at least six to eight inches below the soil surface will block the underground movement of the aggressive rhizomes.
The barrier should also extend a couple of inches above the ground to deter stolons from creeping over the edge. Regular monitoring and immediate spot treatment of any new growth are important for long-term success. If even a small patch of Bermuda grass establishes itself, it will quickly re-invade the entire area.
Maintenance practices also play a significant role in prevention. A thick layer of organic mulch, such as wood chips or shredded bark, should be maintained at a depth of three to four inches across the entire flower bed. This depth suppresses seed germination and blocks sunlight from reaching shallow rhizomes, making it difficult for the plant to gain a foothold. Be mindful of the source of any new soil or mulch brought into the garden, as it may inadvertently introduce dormant Bermuda grass seeds or rhizome fragments.