Bermuda grass (Cynodon dactylon) is a common, aggressive perennial grass often prized for turf but notorious as a tenacious weed in garden beds and cool-season lawns. The challenge lies in eliminating this specific grass species without causing damage to nearby desirable broadleaf plants, flowers, or other turf varieties. This process requires a selective approach, leveraging both chemical and non-chemical strategies that target the grass’s unique biology.
Understanding the Aggressive Nature of Bermuda Grass
Bermuda grass is a warm-season species with a robust growth habit, which explains why surface-level treatments often fail. It spreads rapidly using two types of runners: above-ground stolons and extensive underground rhizomes. The stolons creep along the soil surface, rooting at the nodes to form dense, interconnected mats.
The underground rhizomes are the plant’s primary survival mechanism, able to penetrate deep into the soil, sometimes over two feet. These rhizomes act as energy storage organs, holding reserves that allow the grass to quickly rebound even if the above-ground foliage is destroyed. Successful control requires methods that translocate the killing agent deep into the root structure or physical methods that exhaust these reserves over time.
Selective Chemical Control Methods
Targeting Bermuda grass while sparing other plants relies on the distinct biological difference between grasses (monocots) and broadleaf plants (dicots). Selective herbicides known as “grass-selective” post-emergent graminicides are designed to kill only plants in the grass family, leaving most broadleaf plants unharmed. This makes them ideal for use in garden beds and around established ornamentals.
Control in Broadleaf Areas and Ornamentals
For Bermuda grass invading flower beds, shrub borders, or vegetable gardens, products containing the active ingredients Sethoxydim or Fluazifop are the primary choice. These are systemic herbicides absorbed through the foliage. They move throughout the plant, including down to the rhizomes, disrupting the grass’s growth process. While these herbicides are generally safe for most broadleaf plants, always check the product label for specific varieties that may be sensitive to the chemical.
Control in Non-Bermuda Turf Areas
If Bermuda grass is invading a cool-season lawn (such as fescue, Kentucky bluegrass, or perennial ryegrass), a different selective chemical strategy is needed. Herbicides safe for broadleaf plants will also kill desirable cool-season turf, so the goal shifts to chemicals that selectively injure or suppress warm-season grasses. Products containing Quinclorac are often used to suppress Bermuda grass in these lawns, though multiple applications are necessary for meaningful control. Quinclorac is effective against crabgrass and safe for most cool-season turf types, but its effect on Bermuda grass is usually gradual suppression rather than a complete kill.
Non-Chemical and Cultural Control Methods
For those avoiding herbicides, cultural methods exploit the plant’s reliance on sunlight and its inability to tolerate high temperatures. Soil solarization is a non-chemical technique that uses the sun’s energy to kill the grass and its underground structures. This involves covering the infested area with clear plastic sheeting during the hottest months of the year to raise the soil temperature to levels lethal to the rhizomes and seeds. The plastic should be left in place for a minimum of four to six weeks during peak summer heat.
A similar method is smothering, which uses opaque materials like black plastic sheeting or layers of cardboard topped with mulch to completely block light. Bermuda grass is highly sun-dependent, and the sustained lack of light eventually starves the underground rhizomes of energy. For tough perennial grasses, this smothering technique may need to remain in place for at least one full growing season to fully deplete the extensive energy reserves.
Physical removal is possible, but it is extremely labor-intensive and requires meticulous attention to detail. Every fragment of the rhizomes and stolons left in the soil can potentially grow into a new plant. Strategic planting of dense, taller plants or the installation of shade cloth can also suppress Bermuda grass, as deep shade will weaken the plant over time and reduce its aggressive growth.
Safe Application and Timing Strategies
The success of any Bermuda grass control method, especially chemical, is heavily dependent on precise timing. Post-emergent herbicides must be applied when the Bermuda grass is actively growing, which typically occurs from late spring through summer when temperatures are consistently warm. Applying chemicals to dormant or stressed grass is ineffective because the plant is not actively moving nutrients and water, which prevents the systemic herbicide from translocating to the rhizomes.
For chemical applications, always spot-treat the target grass and avoid windy conditions to prevent herbicide drift onto desirable plants. Using a drift guard or a shield around the spray nozzle can further protect nearby ornamentals. Due to the nature of the rhizomes, repeat applications, often spaced a few weeks apart, are necessary to kill new growth and fully deplete the underground energy stores. Follow-up monitoring and prompt retreatment of surviving patches are necessary for complete eradication.