Tall Fescue is a cool-season bunch grass that frequently invades warm-season Bermuda grass lawns. These invaders remain actively green during the winter and early spring, contrasting sharply with the dormant, brown Bermuda turf. When the Bermuda grass greens up in the summer, the fescue often appears as unsightly, coarse, dark-green clumps that ruin the lawn’s uniform appearance. Success depends on careful identification, accurate timing, and utilizing selective control methods.
Identifying Fescue and Optimal Treatment Timing
Tall Fescue typically exhibits a coarse texture with leaf blades noticeably wider than the fine-bladed Bermuda grass. It also grows in distinct, dense bunches, unlike Bermuda, which spreads horizontally via above-ground stolons and underground rhizomes. The fescue often maintains a darker, almost bluish-green color, which stands out, particularly in the spring when the Bermuda is still emerging from dormancy.
Fescue thrives in cooler temperatures, between 55°F and 75°F, while Bermuda grass prefers heat, between 75°F and 95°F. The most effective time for broad herbicide application is when the Fescue is actively growing, typically in late fall or early spring, but before the Bermuda grass has fully greened up. Targeting the fescue during its active period maximizes herbicide uptake while minimizing damage to the Bermuda turf.
Selective Herbicide Application for Broad Coverage
For widespread infestations, selective post-emergent herbicides are the most practical solution. Products containing the active ingredient Sulfosulfuron are effective, belonging to the sulfonylurea class of herbicides. This systemic chemical is absorbed by the fescue, traveling through the plant to disrupt its growth processes.
Herbicides that contain Imazaquin, which is labeled to selectively remove tall fescue from a Bermuda grass lawn, can also be used. Application should begin after the Bermuda grass has completely broken dormancy and is actively growing, usually in late spring or early summer. Following the initial application, a second treatment is often necessary four to six weeks later to eliminate any surviving fescue plants.
Always adhere strictly to the product label instructions, including application rates and temperature restrictions, as applying herbicides during excessively hot weather can injure the desirable Bermuda turf. Avoid mowing for a few days before and after treatment to allow absorption. Using a non-ionic surfactant with the herbicide mixture can improve chemical adhesion and absorption into the fescue’s coarse leaves.
Non-Chemical and Localized Removal Techniques
The most direct method is physical removal, which involves using a sharp shovel or spade to dig out the entire fescue clump. It is important to remove the entire root ball, as any remaining fescue root or crown tissue can allow the perennial grass to regrow.
For slightly larger, scattered patches, a non-selective herbicide like glyphosate can be used with extreme precision. A precise application using a foam paintbrush or a small sponge dipped in the herbicide solution allows the chemical to be wicked directly onto the fescue leaves.
This localized spot treatment is especially effective in late winter or very early spring when the fescue is actively green but the Bermuda grass is still completely dormant and brown. Alternatively, covering an isolated patch with a thick sheet of clear plastic secured at the edges, a technique known as solarization, can use solar heat to kill the fescue. This method is best performed during the hottest summer months and requires several weeks to be effective.
Maintaining Bermuda Grass Health to Prevent Recurrence
Once the fescue is removed, maintaining a dense, thriving Bermuda lawn is the best long-term prevention strategy. Bermuda grass should be mowed at a low height, typically between 1 and 2 inches, which encourages the grass to spread and thicken. This low cut stresses the upright, cool-season fescue seedlings that may try to germinate, preventing them from establishing.
Proper fertilization is also essential to encourage the Bermuda grass’s aggressive, warm-season growth habit. Applying nitrogen fertilizer during the Bermuda grass’s active growing season, from late spring through summer, promotes lateral spread that crowds out opportunistic weeds.
Ensure the lawn receives deep, infrequent irrigation to promote a strong, deep root system in the Bermuda grass. Finally, consider aeration and overseeding the Bermuda lawn with new seed during the summer months to ensure a completely uniform turf density. A solid, impenetrable turf canopy is the most robust defense against the recurrence of fescue clumps.