Creeping bentgrass (Agrostis stolonifera) is a common and challenging weed for homeowners maintaining a traditional cool-season lawn. While valued for its fine texture on golf course greens, its aggressive, mat-forming growth habit allows it to quickly invade and disrupt the uniform appearance of turf composed of Kentucky bluegrass or fescue. Since bentgrass is a perennial grass, conventional broadleaf weed killers are ineffective. Successful removal requires a targeted, multi-step approach combining cultural practices, manual effort, and sometimes specific chemical treatments.
Identifying Bentgrass in Your Lawn
Creeping bentgrass can be recognized by characteristics that set it apart from most desirable turfgrass species. It possesses a very fine, dense blade texture, which often gives the affected area a soft, almost velvety appearance. This grass typically grows low to the ground and has a lighter green or sometimes a bluish-green color, making patches stand out against a darker green lawn.
The most telling sign is its growth habit, as bentgrass spreads rapidly across the soil surface using above-ground runners called stolons. These stolons enable the plant to form dense, irregular, circular patches or mats that can feel spongy or puffy underfoot. When mowed at typical lawn heights, the fine blades often flop over, creating a matted look that is different from the surrounding turf.
Cultural and Manual Removal Techniques
For small, isolated patches of bentgrass, manual removal provides an immediate, non-chemical solution. The entire plant, including the extensive network of stolons and shallow roots, must be carefully dug out. It is essential to remove the soil six to twelve inches beyond the visible patch to ensure all the creeping runners are eliminated, otherwise the plant will quickly regrow.
Cultural practices focus on creating an environment that favors the desired turfgrasses while discouraging bentgrass, which thrives in high-thatch conditions. Aggressive dethatching or verticutting can physically disrupt the dense mats and stolons. Repeatedly disturbing the bentgrass patches in this manner makes them more susceptible to environmental stress and easier to remove manually.
Solarization involves covering the affected area with clear plastic sheeting during the hottest months. The plastic traps solar heat, raising the soil temperature high enough to kill the bentgrass and its seeds. While effective, this process also kills the desirable turf beneath the plastic and leaves a bare patch that will require reseeding after the treatment is complete.
Targeted Chemical Control Strategies
For severe or widespread infestations, chemical control is often the most practical method. Selective post-emergent herbicides are available that can target bentgrass while minimizing damage to the surrounding cool-season turf, such as Kentucky bluegrass or fescue. Products containing the active ingredient mesotrione are recommended for this purpose.
Mesotrione works by disrupting photosynthesis in susceptible plants, causing the bentgrass to turn a noticeable white color before it dies. This treatment typically requires a program of two to three applications, spaced two to three weeks apart, to achieve effective control. The applications are most effective when the bentgrass is actively growing, typically in mid to late summer or early fall.
For homeowners dealing with large, solid patches or considering a complete renovation, a non-selective herbicide containing glyphosate can be used. This chemical kills all vegetation it contacts, offering a guaranteed kill of the bentgrass and its stolons. When using this method, the herbicide must be sprayed slightly beyond the visible patch to ensure the entire network of runners is eliminated. The area will then need to be reseeded or sodded after the bentgrass has died and been cleared away.
Maintaining a Bentgrass-Free Lawn
After removing bentgrass, long-term control requires adopting cultural practices that create an inhospitable environment for its return. Since bentgrass thrives when mowed short, raising the mowing height to three inches or more is an effective preventative measure. Taller grass blades shade the soil, reducing the light bentgrass needs to germinate and spread.
Lawns should be watered deeply and infrequently, rather than lightly and frequently. This practice discourages the shallow-rooted bentgrass and encourages the deeper root systems of desirable turfgrasses, making them more competitive.
Overseeding bare or thinned areas with high-quality seed prevents bentgrass from establishing a foothold. Maintaining an appropriate fertilization schedule further helps the lawn resist new infestations.