Bermuda grass (Cynodon dactylon) is a warm-season grass valued for its drought tolerance and resilience in lawns. However, its aggressive growth transforms it into a problematic, invasive weed when it spreads into ornamental flower beds. Its rapid lateral expansion can quickly choke out delicate perennials and shrubs. Effectively removing this persistent grass requires understanding its unique biology and employing systematic, non-chemical strategies to reclaim your flower beds.
Understanding Why Removal is So Difficult
Bermuda grass is difficult to remove because it spreads rapidly using two types of vegetative reproduction. Above the surface, horizontal stems called stolons creep along the ground, rooting at nodes to form new plants. These runners quickly invade neighboring areas, including edging and pathways.
Below the surface, the plant uses rhizomes, which are modified underground stems that store energy. These rhizomes can extend several inches deep, sometimes reaching depths of 6 to 12 inches. Since both stolons and rhizomes contain nodes capable of sprouting new growth, chopping them into pieces with a rototiller or shovel only propagates the grass further. Complete eradication requires removing every fragment of these structures.
Non-Chemical Eradication Methods
Physical Removal
The most effective, targeted method for existing flower beds is systematic physical removal. Begin by loosening the soil surrounding the infestation using a garden fork rather than a shovel, as the fork minimizes the risk of slicing the rhizomes. Carefully lift the soil and grass mass, gently shaking it to expose the tangled network of rhizomes and stolons.
The goal is to follow each runner back to its source and pull it out whole, ensuring no small pieces remain. To achieve thoroughness, sifting the loosened soil through a screen or hardware cloth helps capture smaller fragments. Dispose of all removed grass material in the trash, as fragments left in a compost pile can survive and re-infest the area.
Smothering Techniques
If the flower bed is heavily infested or you are preparing a new area, smothering techniques can kill the grass in place. Solarization uses clear plastic sheeting (4 to 6 mil thick) to trap solar energy and raise the soil temperature to lethal levels. This method requires 6 to 8 weeks during the hottest part of the summer to be successful. The plastic must be securely sealed around the edges to prevent heat loss.
A less intensive option is occultation, which involves using thick layers of overlapping cardboard covered by several inches of mulch. This blocks all sunlight, starving the grass of energy needed for photosynthesis. While effective and beneficial for soil, this method requires a longer duration, often four to six months or more, before the area is safe for planting. Chemical options are generally avoided because Bermuda grass requires a non-selective herbicide that would also kill desirable ornamental plants.
Structural Barriers and Long-Term Prevention
Installing Edging
Once the flower bed is cleared, the focus shifts to preventing re-entry from surrounding lawn areas by installing deep, solid edging. Since Bermuda grass rhizomes can creep several inches below the surface, the physical barrier must extend at least 6 inches into the ground. A total barrier height of 10 inches is recommended, with 6 inches buried and approximately 4 inches remaining above the soil line to block stolons from crawling over the top.
Materials like heavy-gauge plastic, metal flashing, or solid concrete edging are suitable for this purpose, creating an impenetrable wall against the underground runners. Even with a barrier in place, consistent maintenance is necessary to stop the above-ground stolons. The area immediately adjacent to the flower bed barrier should be routinely mowed or edged to prevent the runners from scaling the barrier and dropping into the flower bed.
Maintaining the Buffer Zone
A buffer zone, such as a shallow trench filled with gravel or a strip of hardscaping, can be established outside the barrier. This creates a hostile environment for the creeping stems. Finally, a thick layer of organic mulch, maintained at a depth of three to four inches, will suppress stray seedlings and make new growth easier to spot and remove. Avoid using fresh Bermuda grass clippings as mulch, as they may contain viable runners or seeds that can re-establish the infestation.