Bermuda grass can provide a durable, green lawn, especially if you live in a southern state. Tenacious, with some drought tolerance, Bermuda grass spreads rapidly and sinks thirsty roots. The only problem with Bermuda grass is that same tenacity and aggressive spreading tendencies. Edging is often needed to keep Bermuda within bounds, out of flower beds and off driveways.
Bermuda Grass Virtues
Bermuda grass (Cynodon dactylon) is valued in situations requiring heat- and drought-tolerance. Of African origin, Bermuda grass forms a thick turf that tolerates high traffic, even in areas where soil may be shallow. These qualities make it ideal not only for lawns but also for playing fields and golf courses in southern states in USDA hardiness zones 9, 10 and 11. Some new varieties are more cold-tolerant, expanding the use of Bermuda grass to transitional hardiness zones, ranging from 6 to 8.
Bermuda Turf Formation
While grasses generally spread by both seed and root, Bermuda grass roots run notably deep and form vigorous rhizomes at depths of 6 inches or more. This permits survival in dry, hot conditions but also means that expansion of Bermuda grass cannot be handled as a surface turf problem.
Potential Containment Strategies
Management of Bermuda grass spreading on playing fields and golf courses may involve deep trenching and chemical containment strategies. In a residential yard, mechanical and physical barriers can replace herbicide controls. Regular mowing and trenching techniques limit out-of-bounds growth. Metal, plastic, stone and concrete barriers can also be used, with some planning.
Planning Physical Barriers
Physical barriers need to be deep and continuous to keep Bermuda grass under control. Edging a driveway or flower bed with brick, Belgian block or concrete pavers produces handsome results, but Bermuda rhizomes will seek out gaps, no matter how small, between these edging blocks and grow through them aggressively. Metal and plastic edgings can set better limits, so long as they are set to a minimum depth of 6 inches, and preferably 12 inches. Rhizomes will travel under shallower edgings and continue grass growth on the other side.
Concrete Barrier Issues
Use of concrete curbing satisfies the continuous requirement of Bermuda grass barriers. The few joints needed for curbing can be monitored and cleaned on a regular basis. The main problem with concrete edging, however, is depth. Prefabricated concrete curbing may be physically difficult to set at depths of more than 4 to 6 inches. Professional continuous curbing can be set at greater depths but may involve considerable time and prohibitive expense.
One landscape architect, Bruce Holliday of Atlanta, suggests combining brick and concrete in a continuous curb. Adequate depth to control rhizome spread is achieved by setting a soldier row of brick under the brick/concrete curbing. He also suggests maintaining a 4-by-4 inch trench to deter unwanted grass growth but notes that this will require weekly maintenance. Another strategy gained from golf-course management is to use another type of grass as a barrier between Bermuda and the areas you want to keep free of grass. Bordering your Bermuda grass "rug" with a 2- to 3-foot border of a less aggressive grass may be an aesthetically tolerable way to cover large areas with a vigorous grower while keeping the edges under control.