Bahia grass (Paspalum notatum) is a warm-season perennial known for its aggressive growth habit, often becoming a persistent weed in managed turf areas. It thrives in the sandy, nutrient-poor soils of the southern United States, spreading vigorously through seeds and underground stems. The grass’s coarse texture and tough, rapidly growing seed heads compromise the turf’s appearance shortly after mowing. Removing Bahia grass without damaging the surrounding turf requires a selective and well-timed control strategy, including specific identification, cultural practices, and chemical treatments.
Identification and Seasonal Growth Cycle
Bahia grass is distinguishable from most cultivated turfgrasses by several features. The plant forms a sparse, light-green canopy with coarse leaves that are folded or V-shaped at the base. Its most noticeable feature is the distinct, slender seed head, which usually consists of two spike-like branches forming a recognizable “Y” or “V” shape at the top of a tall stalk.
As a warm-season grass, its active growth period begins in late spring and continues through the summer months. Its perennial nature means the plant has underground rhizomes, allowing it to survive winter dormancy and re-emerge annually. Control measures are most effective when applied while the grass is actively growing and translocating nutrients to its roots.
Non-Chemical Suppression Techniques
A healthy, dense lawn canopy suppresses the establishment of Bahia grass seedlings. Maintaining the desirable turf at the upper end of its recommended mowing height helps achieve this density. Taller turf shades the soil surface, blocking the sunlight that Bahia grass seeds require for germination.
Proper irrigation techniques also help suppress this drought-tolerant weed by favoring the cultivated turfgrass. Instead of frequent, light watering, the lawn should be watered deeply but infrequently to encourage the turfgrass to develop a deep root system. This practice stresses the shallower-rooted Bahia grass while strengthening the desirable lawn species.
A fertilization program should meet the needs of the desirable turfgrass species. Applying fertilizer based on soil test results promotes a vigorous, thick lawn that can outcompete the weed for light, water, and nutrients. Since Bahia grass is adapted to low-fertility conditions, over-fertilizing can inadvertently benefit the weed, requiring a balanced approach.
Selective Herbicide Options Based on Desirable Grass Type
Controlling Bahia grass without harming the existing lawn requires selecting post-emergent herbicides, as different turf species have varying tolerances to active ingredients. Application must be timed to the weed’s active growth phase (late spring through summer) to ensure the herbicide moves effectively throughout the plant, including the rhizomes. Repeat applications, often spaced four to six weeks apart, are necessary for complete control of this persistent perennial.
Bermuda and Zoysia Grass
For Bermuda and Zoysia lawns, the active ingredient metsulfuron-methyl is a selective option for controlling Bahia grass. This herbicide is tolerated well by both turf species when applied according to label instructions. Temporary yellowing or stunting of the desirable grass may occur, particularly if a non-ionic surfactant is added to enhance penetration.
Imazaquin is another selective herbicide option that aids in control and reduces competition in established Bermuda and Zoysia lawns. Avoid applying imazaquin during the spring transition, which is when the desirable grass is actively greening up from winter dormancy. Ensure the lawn is fully established and actively growing before application to minimize potential turf injury.
St. Augustine and Centipede Grass
St. Augustine and Centipede grasses are sensitive to chemical treatments, limiting the selection of herbicides. For these turf types, the active ingredient atrazine is a selective option, offering post-emergence control of existing Bahia grass. Atrazine also provides residual, pre-emergence activity to help control newly germinating seeds.
Metsulfuron-methyl is also safe for use on St. Augustine and Centipede grasses, though Centipede often requires a reduced application rate due to its sensitivity. Centipede lawns can also be treated with sethoxydim, which suppresses Bahia grass growth and seed head development. Due to the sensitivity of these species, follow the product label’s instructions regarding application rates and temperature restrictions to avoid damaging the turf.
Grasses to Avoid
Selective herbicides used for controlling broadleaf weeds, such as three-way herbicides containing 2,4-D, dicamba, and mecoprop, are not effective against grassy weeds like Bahia grass. Atrazine should be avoided in Bermuda grass lawns, as it can cause severe injury to that species. Tall Fescue is also intolerant to many selective herbicides used against Bahia grass, making control difficult without causing turf damage.
Post-Treatment Lawn Recovery and Prevention
Following herbicide application, the treated Bahia grass will turn yellow and die, often leaving bare or thin spots in the lawn. To prevent new weeds from establishing, fill these open areas with plugs or sprigs of the desirable turfgrass species. Herbicides like metsulfuron-methyl can have a soil residual effect, requiring a waiting period of up to eight weeks before attempting to re-seed or re-sod the area.
Long-term prevention relies on maintaining a thick and healthy lawn through cultural practices. Regular aeration and topdressing can improve soil health and drainage, benefiting the cultivated turfgrass over the weed. The goal is to maximize the density of the lawn canopy, creating a living barrier that physically prevents Bahia grass seeds from reaching the soil and germinating.