If you love your fescue (Festuca arundinacea) lawn, which grows in U.S. Department of Agriculture plant hardiness zones 3 through 8, it might be hard to keep it free of Bermuda grass (Cynodon dactylon) in the warmer ranges of fescue's hardiness areas. Bermuda, which thrives in USDA zones 7 through 10, can be so invasive it's often considered a weed. However, if you're looking for a low-maintenance, warm-weather grass, you don't have to remove your fescue to replace it with Bermuda -- the Bermuda grass can take over all on its own.
The Bermuda Takeover
Many people enjoy Bermuda grass lawns because of their ease of care. It handles low, infrequent mowings -- even down to 1/2 inch high -- and it's drought tolerant. It springs back after you walk on it, making it durable for heavy traffic. Even small plugs can spread rapidly, sending out underground stolons in every direction to choke out other plants and allow new Bermuda blades to grow. As a warm-season grass, this hostile takeover can continue all summer.
Why Fescue Can't Fight
Fescue, while relatively hardy, isn't as aggressive as Bermuda grass. As a cool-season grass, fescue is attacked by Bermuda when it's at its weakest -- during the long, hot summer. In the shade, fescue might still hold its own, but Bermuda thrives on sunlight and quickly invades fescue-filled, sunlit areas. Bermuda's underground rhizome system creates a tight net, which steals nutrients from the fescue, making it even weaker.
Because Bermuda is so invasive, it's definitely a battle to keep it from overtaking your fescue. It's difficult, but not impossible. Mow your grass at a height where fescue flourishes, such as 2 to 3 inches tall. This won't hurt the Bermuda grass, but it gives the fescue an opportunity to stay strong. Spray clumps of Bermuda grass with a non-selective herbicide such as glyphosate. This might leave small bare areas on your lawn, but the fescue will quickly fill in these spots when cooler weather arrives. Overseed the lawn with fescue in the fall to create a stronger lawn for the spring.
Farewell to Fescue
Sometimes, it's easier to throw in the towel and let the Bermuda grass make its home in your yard, says Walter Reeves on his website. Mow the lawn to about 1 inch high. Fescue doesn't survive well with short blades. Apply a high-nitrogen fertilizer, such as a 16-4-8, in the late spring and early fall to encourage the Bermuda stolons to grow. Water lightly and infrequently; Bermuda rhizomes won't be harmed by light watering, but fescue roots become weaker as they gravitate toward the soil's surface in search of moisture.