Removing Bermuda grass from a St. Augustine lawn requires either selective herbicides that exploit the biological differences between the two grasses or cultural tactics that tilt the playing field in St. Augustine’s favor. The good news is that several chemical and non-chemical approaches can work, but none of them deliver overnight results. Bermuda grass spreads through both above-ground runners and underground stems, so any plan that only addresses what you can see on the surface is going to fail. Expect a campaign lasting at least one full growing season, and often two, before your St. Augustine lawn is truly clear.
Why Bermuda Grass Is Such a Stubborn Invader
Bermuda grass earned its reputation as one of the most aggressive warm-season turf species for good reason. It spreads in two ways simultaneously: stolons that creep along the soil surface and rhizomes that travel underground, sometimes several inches below the turf line. Cut a stolon, and the rhizome sends up new shoots. Kill the visible blades, and buried rhizome nodes can push new growth weeks later. This dual spreading habit is what makes Bermuda grass so difficult to eradicate compared to weeds that only spread by seed or by a single runner type.
St. Augustine grass, by contrast, spreads almost entirely by stolons. It forms a dense canopy that shades the soil surface, which is actually one of its built-in defenses against Bermuda grass invasion. But once Bermuda grass gets a foothold, whether from a neighbor’s lawn, contaminated sod, or seed blown in by mowers, it threads its way through the St. Augustine mat and becomes entangled at the root level. At that point, you cannot simply pull it out without tearing up large patches of your desired turf.
Selective Herbicides That Kill Bermuda but Spare St. Augustine
The cornerstone of most Bermuda grass removal programs in St. Augustine lawns is a selective herbicide, meaning a product that targets one grass species while leaving the other largely unharmed. This is possible because the two grasses absorb and process certain chemicals at very different rates.
Ethofumesate
Ethofumesate has been the go-to active ingredient for selective Bermuda grass suppression in St. Augustine turf for decades. Research has shown that the rate of ethofumesate needed to reduce Bermuda grass shoot mass by half is dramatically lower than the rate needed to harm St. Augustine. In greenhouse trials, Bermuda grass reached that 50-percent reduction point at a relatively low application rate, while St. Augustine required more than seven times as much product to reach the same level of damage.1Crop Science. Physiological Basis for Bermudagrass Control with Ethofumesate in Seashore Paspalum and St. Augustinegrass That wide margin is what makes selective control possible.
The reason for this gap comes down to absorption. Bermuda grass takes in substantially more ethofumesate through both its roots and its foliage than St. Augustine does. On top of that, St. Augustine translocates roughly 20 percent less of the absorbed chemical to its shoots compared to the other grasses, which further protects its above-ground growth.2Crop Science. Physiological Basis for Bermudagrass Control with Ethofumesate in Seashore Paspalum and St. Augustinegrass In field settings, ethofumesate applied during warm months has delivered good control, in the range of 80 to 89 percent Bermuda grass reduction, when used alone.3Crop Science. Selective Control of Common Bermudagrass in St. Augustinegrass
For homeowners, ethofumesate is found in products typically sold under names like “Bermudagrass Control for St. Augustinegrass” at garden centers. Applications usually need to be repeated two or three times during the growing season, spaced a few weeks apart, because rhizomes that escape the first application will send up new growth. A single pass rarely finishes the job.
Fluazifop-P-Butyl
Fluazifop is a grass-specific herbicide that targets narrow-leaved grasses more aggressively than broader-bladed species. Because Bermuda grass has finer blades and a different metabolic pathway for processing this chemical than St. Augustine, fluazifop can suppress Bermuda grass with acceptable safety to the host lawn. It is sometimes used in combination with other products for broader-spectrum Bermuda control.
One limitation is that fluazifop can cause temporary yellowing or thinning in certain St. Augustine cultivars, particularly if applied at high rates or during periods of heat stress. This is where newer formulations come in.
Newer Safened Formulations
A product called Recognition has entered the market specifically for this exact problem. It pairs trifloxysulfuron-sodium, which is a sulfonylurea herbicide effective against Bermuda grass, with a chemical safener called metcamifen. The safener’s job is to protect the St. Augustine from injury that the active ingredient might otherwise cause. This safened formulation is designed to be tank-mixed with fluazifop-P-butyl, allowing homeowners and lawn care professionals to hit Bermuda grass with two complementary modes of action while minimizing damage to the St. Augustine turf.4International Turfgrass Society Research Journal. Safety of Recognition‐based tank‐mixes with fluazifop‐P‐butyl on selected St. Augustinegrass cultivars in Florida
The concept of a safener is worth understanding because it changes the practical calculus. Older herbicide programs for Bermuda grass removal relied on a single active ingredient and needed to stay within a narrow dosage window to avoid hurting the St. Augustine. A safener effectively widens that window, which means better Bermuda grass kill rates with less risk to the turf you want to keep. This approach is relatively new in the residential turf market, and availability varies by region.
Using Shade as a Weapon
If chemicals are not your first choice, or if you want to complement a herbicide program, shade is one of the most effective cultural tools you have. Bermuda grass is essentially a sun-addicted species. Its performance drops sharply when light levels decrease, and research consistently shows it cannot maintain acceptable turf quality under even moderate shade. In trials evaluating multiple turf species under graded shade levels, Bermuda grass performance was rated unsatisfactory under reduced light conditions.5The Indian Journal of Agricultural Sciences. Growth and physiological potential of various turf grass species under graded shade levels
St. Augustine, on the other hand, handles shade remarkably well. In separate studies evaluating turfgrass shade tolerance, St. Augustine maintained consistent turf quality and relatively uniform shoot density across full sun, 35 percent shade, and 50 percent shade conditions, while Bermuda grass varieties showed limited adaptability once shade was introduced.6Plant Archives. EVALUATING TURFGRASS SHADE TOLERANCE FOR SUSTAINABLE URBAN LANDSCAPES This difference gives you a genuine strategic advantage if your landscape includes trees, structures, or other shade sources.
In practical terms, this means encouraging tree canopy growth, planting shrubs along borders where Bermuda grass invades from a neighbor’s yard, or even installing shade structures over problem areas. Bermuda grass struggling in shade produces thinner, weaker runners that are easier for a healthy St. Augustine mat to outcompete. Over several seasons, consistent shade can tip the competitive balance without any chemical input. The obvious limitation is that you cannot shade an entire open lawn, so this tactic works best as a complement to other methods or for specific trouble zones near fence lines and landscape borders.
The Nuclear Option With Glyphosate
When Bermuda grass has completely overtaken large sections of the lawn, selective herbicides may be too slow or too incremental to make a practical difference. In these cases, some homeowners resort to glyphosate, the non-selective herbicide that kills virtually all actively growing plants it contacts. The approach involves killing everything in the infested area and then re-establishing St. Augustine from sod or plugs once the Bermuda grass is fully dead.
This scorched-earth approach has a serious catch. Bermuda grass is tenacious enough that a single glyphosate application rarely eliminates it. Research on glyphosate injury to forage bermudagrass found that even at higher application rates, the relationship between the rate applied and the degree of injury was not straightforward, with regrowth occurring after treatment.7MDPI Agronomy. Assessing Glyphosate Injury and Forage Bermudagrass Regrowth Using Canopeo Rhizomes buried deeper in the soil can survive the initial application and push new shoots within weeks. Most lawn renovation guides recommend at least two glyphosate applications spaced two to three weeks apart, with a third follow-up if any green regrowth appears.
The timing matters here too. Glyphosate works best on Bermuda grass when the grass is actively growing and photosynthesizing, because the plant needs to be pulling the chemical down through its system into the root and rhizome network. Applications made during cool months when Bermuda grass is dormant or semi-dormant will have little effect. The ideal window in most southern climates is late spring through early fall, when daytime temperatures are consistently above 80°F and the Bermuda grass is at peak metabolic activity.
After you are confident the Bermuda grass is fully dead (wait until you see no regrowth for at least three to four weeks after the last treatment), you can lay St. Augustine sod over the treated area. Be thorough about inspecting the edges, because Bermuda grass that survived in the periphery will recolonize fresh sod quickly.
Manual and Mechanical Removal
Pulling Bermuda grass by hand or digging it out with a flat shovel is a method that works only in very small infestations. If you have a few isolated runners threading into a flower bed adjacent to your St. Augustine lawn, you can trace the stolon back to its source and remove the entire runner, including as much of the underground rhizome as you can extract. For anything larger than a few square feet, manual removal becomes impractical because you will inevitably leave behind rhizome fragments, and each fragment has the ability to regenerate a new plant.
Solarization is sometimes suggested as a manual alternative to herbicides. The idea is to cover the infested area with clear plastic sheeting during the hottest months, trapping heat underneath to cook the grass and its root system. Solarization can reach temperatures high enough to kill surface runners, but Bermuda grass rhizomes buried several inches deep may survive. If you try this method, leave the plastic in place for at least six to eight weeks during peak summer heat, and expect to follow up with spot treatments for any regrowth. It works best as a supplement to other strategies rather than a standalone solution.
Timing Your Campaign
When you start your removal effort matters almost as much as which method you choose. Bermuda grass is a warm-season species that goes dormant in winter across much of its range, turning straw-brown and ceasing active growth. You might be tempted to attack during dormancy, but most herbicides are less effective on dormant turf because the plant is not actively transporting chemicals through its system.
The best time to begin a selective herbicide program is in late spring, once the Bermuda grass has broken dormancy and is putting out vigorous new growth. Applications made from May through August generally yield the strongest results. Plan for two to three applications spaced about four to six weeks apart. A fall follow-up can catch survivors before winter dormancy, setting you up for a cleaner start the following spring.
For the glyphosate renovation approach, start in late spring as well, but budget for a longer timeline. Two to three applications over six to eight weeks, followed by a recovery period, followed by sod installation means you are looking at a window of about three months from first spray to new lawn. If you start in May, you should have fresh sod down by August, which gives the St. Augustine time to establish roots before cooler weather arrives.
One often-overlooked timing tip: mow your St. Augustine at the tallest recommended height (around 3.5 to 4 inches) throughout the removal process. This maximizes the canopy shade at the soil surface, which stresses Bermuda grass runners trying to compete for light, as described earlier. It also helps the St. Augustine recover faster from any mild herbicide stress it may experience.
Preventing Bermuda Grass From Coming Back
Killing the Bermuda grass you have now is only half the battle. Reinfestation is extremely common because Bermuda grass spreads aggressively from neighboring properties, along roadsides, and even from small seed deposits carried by wind, animals, or mowing equipment. If your neighbor’s lawn is full Bermuda turf, you will be fighting an ongoing border war.
Physical barriers can help. Installing root barriers (rigid plastic edging buried at least six inches deep) along property lines and garden borders can slow or block underground rhizome encroachment. These barriers need to be continuous and free of gaps, because a single opening is all Bermuda grass needs to send a runner through.
Maintaining a thick, healthy St. Augustine canopy is your best long-term defense. A dense St. Augustine lawn that is properly fertilized, irrigated, and mowed at the right height will shade the soil surface heavily enough to suppress Bermuda grass seedlings before they establish. When St. Augustine thins out due to disease, drought stress, insect damage, or scalping from a mower set too low, those bare spots become open invitations for Bermuda grass to move back in.
Spot-treating any Bermuda grass you see as soon as it appears is far easier and more effective than waiting until it has spread across an entire section. Keep a small bottle of selective herbicide on hand during the growing season and treat individual runners when they are still isolated. This “seek and destroy” maintenance approach is the single most practical habit for keeping a St. Augustine lawn Bermuda-free after the initial eradication effort.
What About Bermuda Grass in Floratam and Other St. Augustine Cultivars
St. Augustine grass comes in several cultivars, and they do not all respond identically to the herbicides used to control Bermuda grass. Floratam, Palmetto, Seville, CitraBlue, and Bitter Blue are among the most widely planted varieties in the southern United States, and each has its own degree of tolerance to products like ethofumesate, fluazifop, and the newer safened formulations. Research on Recognition-based tank mixes, for instance, was specifically conducted on selected St. Augustine cultivars in Florida to evaluate whether the safener adequately protected different varieties.4International Turfgrass Society Research Journal. Safety of Recognition‐based tank‐mixes with fluazifop‐P‐butyl on selected St. Augustinegrass cultivars in Florida
Before committing to a herbicide program, you should know which cultivar of St. Augustine you have. This is not always easy to determine by eye, especially if the lawn is several years old and multiple cultivars have been patched in over time. If you are uncertain, contact your county extension office. They can usually identify your cultivar from a sample and recommend the safest herbicide option for it. Applying a product that has been tested primarily on Floratam to a Seville lawn, for example, could result in more injury than you expected.
Dwarf St. Augustine varieties like Seville tend to have finer blades and denser growth habits that are somewhat closer to Bermuda grass in appearance, which can make it harder to distinguish the invader from the host when scouting. Learning to recognize Bermuda grass by its seed heads, which are distinctive finger-like spikes that radiate from a central point, is one of the more reliable field identification tricks. St. Augustine seed heads are much less common and look quite different when they do appear.
When Bermuda Grass Might Actually Be the Better Choice
This is the part nobody writes on the label, but it is worth considering honestly. If your yard is full sun with no shade structures or trees, and your Bermuda grass infestation is extensive, you might be fighting against the natural competitive advantage of the site. Bermuda grass thrives in open, high-light conditions where it consistently outperforms most other warm-season turf species, including St. Augustine.6Plant Archives. EVALUATING TURFGRASS SHADE TOLERANCE FOR SUSTAINABLE URBAN LANDSCAPES St. Augustine will grow fine in full sun, but it does not have the same aggressive competitive edge there that it enjoys in partial shade.
In a yard with very limited shade and persistent Bermuda grass pressure from surrounding properties, the cost and labor of repeated herbicide applications, renovation, and ongoing maintenance can add up to hundreds or even thousands of dollars over several years. For some homeowners, the pragmatic decision is to accept the Bermuda grass, convert the lawn entirely to an improved Bermuda variety, and stop fighting a losing ecological battle. Improved Bermuda cultivars bred for residential lawns have finer texture, better color, and lower growth habits than the common Bermuda grass that typically invades. The conversion avoids the endless cycle of eradication and reinfestation, though it comes with its own trade-off: Bermuda grass requires more frequent mowing and goes dormant to a straw-brown color in winter across most of its range, which bothers some homeowners more than others.