How to Kill Weeds in Bermuda Grass

Bermuda grass tolerates most common lawn herbicides better than the weeds you are trying to eliminate, which gives you a genuine advantage. The key is matching the right product and timing to the type of weed: broadleaf invaders like dandelions and clover fall to widely available selective herbicides, while grassy weeds like crabgrass and goosegrass require a more strategic combination of pre-emergent barriers and cultural practices. The details matter more than most homeowners realize, from soil temperature windows to something as overlooked as the quality of your tap water in the spray tank.

Why Bermuda Grass Gives You an Edge

Bermuda grass is one of the most aggressive warm-season turfgrasses. It spreads by both stolons (aboveground runners) and rhizomes (underground runners), which means it fills in bare spots faster than most weeds can colonize them. That growth habit is exactly why bermuda can be a nightmare when it escapes into flower beds but a real asset when you are trying to crowd out weeds in your lawn. A thick, healthy bermuda stand is itself a weed-suppression tool. Many of the herbicides that would damage cool-season grasses like fescue or bluegrass are safe on bermuda, so you have a wider chemical toolkit at your disposal.

That said, bermuda’s vigor works against you if the lawn thins out. Compacted soil, shade, drought stress, or mowing too low can open gaps in the canopy, and weeds rush in. The most effective weed-control program in bermuda grass is really a two-track strategy: chemical treatments for what is already there and cultural practices that keep the turf dense enough to prevent new weeds from establishing.

Broadleaf Weeds Are the Easier Fight

Dandelions, clover, henbit, chickweed, dollarweed, and other broadleaf weeds are the most straightforward to kill in bermuda grass. Selective broadleaf herbicides containing 2,4-D, dicamba, or MCPP (often sold as “three-way” mixtures) target broadleaf plants without harming grasses. You can buy these as ready-to-spray bottles or hose-end concentrates at any garden center. They work by mimicking plant growth hormones, causing broadleaf weeds to grow themselves to death while grasses shrug off the effect.

A practical detail worth knowing: if you have kids, pets, or anyone who uses the lawn after treatment, irrigating the turf after applying a product like 2,4-D significantly reduces the amount of chemical that can be picked up from the grass surface. Research on hybrid bermudagrass athletic fields found that a single irrigation event after 2,4-D application cut dislodgeable residues by more than half, and by two days after treatment, irrigated plots had almost negligible surface residue compared to non-irrigated plots where measurable residue persisted for a week or more.¹ So watering lightly after a broadleaf herbicide application is not just good for pushing the product to the roots; it also reduces surface exposure.

For best results, spray broadleaf herbicides when weeds are actively growing, air temperatures are between roughly 60°F and 85°F, and no rain is expected for at least a few hours. Applying in extreme heat can stress bermuda grass, and applying when weeds are dormant wastes product.

Grassy Weeds Require a Different Approach

Crabgrass, goosegrass, annual bluegrass (Poa annua), dallisgrass, and other grassy weeds are harder to kill in bermuda because they are physiologically similar to the turf itself. A broadleaf herbicide will not touch them. You have two main lines of attack: pre-emergent herbicides that stop weed seeds from germinating, and post-emergent herbicides that target specific grassy species after they appear.

For crabgrass and goosegrass, pre-emergent herbicides are the backbone of control. Products containing prodiamine, pendimethalin, or dithiopyr create a chemical barrier in the top layer of soil that kills germinating seedlings before they break the surface. Timing is everything: you need the barrier in place before soil temperatures hit the germination threshold for the target weed, which is roughly 55°F at a four-inch depth for crabgrass. A split application, half in early spring and the other half six to eight weeks later, often provides longer-lasting coverage than a single heavy dose.

Poa annua, or annual bluegrass, is a cool-season grassy weed that plagues bermuda lawns primarily in fall and winter when bermuda is going dormant. Research tracking Poa annua emergence found that the most rapid germination occurred between roughly the 40th and 43rd weeks of the year (early to mid-October in most of the U.S.), when seven-day average soil temperatures at two inches deep hovered around 66°F and weekly rainfall averaged about half an inch.² That means your fall pre-emergent application needs to be down before early October in most transition-zone and southern climates. Miss that window and you are chasing emerged seedlings with less effective post-emergent options.

Poa annua is also developing resistance to multiple herbicide classes, which makes integrated management, rotating chemistries and combining chemical and cultural approaches, increasingly important.³

Post-Emergent Options for Grassy Weeds You Missed

If crabgrass or goosegrass has already established, you still have options, but they narrow quickly. Quinclorac is one of the few post-emergent herbicides that can kill young crabgrass without harming bermuda grass. It works best on crabgrass with fewer than four tillers; once the plant matures, control drops sharply. For goosegrass specifically, products containing metribuzin or combinations with MSMA (where still legally available) have been used, but label restrictions on MSMA have tightened considerably in recent years.

Dallisgrass is a perennial grassy weed that no single herbicide knocks out reliably in bermuda. Repeated applications of MSMA or foramsulfuron over multiple growing seasons can weaken it, but many homeowners end up spot-treating with a non-selective herbicide like glyphosate, accepting a temporary brown patch, and letting the bermuda fill back in. Bermuda’s aggressive spreading habit makes this approach more viable than it would be in slower-growing turf types.

Mowing Height as Weed Control

One of the most underrated weed-control tools in bermuda grass costs nothing extra: adjusting your mower. Bermuda thrives when mowed at one to two inches, and maintaining it at the higher end of that range during peak weed-pressure periods creates a denser canopy that physically shades out weed seedlings.

Research on goosegrass competition with bermuda grass demonstrated this clearly. When bermuda was mowed at about one inch versus two and a half inches, the higher mowing height reduced goosegrass seedling emergence by 58%.⁴ The mechanism is straightforward: a taller, denser bermuda canopy intercepts more light, and goosegrass seeds need light to germinate and establish. If you scalp your bermuda down to half an inch because you like the golf-course look, you are rolling out the welcome mat for weeds unless you are also running a professional-grade pre-emergent program.

Mowing frequency matters too. Bermuda grows fast in summer and benefits from being cut every four to five days during peak growth. Letting it get shaggy and then whacking it back hard stresses the turf and creates opportunities for weeds. The goal is to never remove more than a third of the blade height in a single mowing.

Soil Compaction and High-Traffic Zones

If you have areas of your bermuda lawn that always seem weedy no matter what you do, soil compaction may be the underlying problem. Paths where people walk, spots where the kids play, edges near driveways: these zones get compressed over time, and the soil structure changes in ways that favor certain weeds over bermuda.

The same goosegrass study found that goosegrass density and cover were higher in trafficked, compacted plots compared to non-trafficked plots. Interestingly, bermuda’s root weight was reduced by compaction when growing alongside goosegrass, while goosegrass roots were unaffected, meaning compaction tilts the competitive balance in the weed’s favor.⁴ The researchers concluded that canopy cover, rather than compaction alone, was the main factor explaining goosegrass infestation in trafficked areas. In other words, compaction weakens the bermuda canopy, and the thinner canopy is what lets weeds in.

The fix is core aeration. Pulling plugs of soil once or twice a year, ideally in late spring or early summer when bermuda is growing vigorously, loosens compacted soil and lets bermuda’s roots expand. It is not glamorous work, but in persistently weedy high-traffic areas, aeration often does more lasting good than another round of herbicide.

Temperature, Herbicide Safety, and Bermuda Stress

Bermuda grass is heat-loving, but herbicide applications at extreme temperatures can still cause damage. The general rule is to avoid spraying most post-emergent herbicides when air temperatures exceed 90°F. At high temperatures, bermuda’s metabolism changes in ways that can increase herbicide absorption and reduce the plant’s ability to detoxify the chemical before it causes injury.

Research on amicarbazone, a herbicide sometimes used for Poa annua control in warm-season turf, illustrates the principle. At moderate temperatures, bermuda grass absorbed less of the herbicide through its foliage and metabolized a greater share of what it did absorb compared to the target weed. But at elevated temperatures (around 104°F day/95°F night in the study), foliar absorption increased across all species, narrowing the safety margin between killing the weed and injuring the turf.⁵ The practical takeaway is simple: spray in the morning before the heat peaks, or wait for a cooler day. A few degrees of air temperature can be the difference between clean weed control and a burned lawn.

Your Spray Water Might Be Working Against You

Here is something most homeowners never consider: the water you mix your herbicide with can reduce its effectiveness before it ever hits a weed. Hard water, which is common in much of the southern and western U.S. where bermuda lawns are most popular, contains calcium and magnesium ions that can bind with certain herbicide molecules and reduce their availability to the plant.

A review of spray-water quality effects on herbicide performance found that hardness, pH, alkalinity, turbidity, and total dissolved solids can all influence how well post-emergent herbicides work, with hard water particularly reducing the efficacy of weak-acid herbicides.⁶ Many common lawn herbicides fall into the weak-acid category. If you have been frustrated by inconsistent results from post-emergent sprays, your well water or municipal water supply might be part of the problem.

The fix is inexpensive. Adding a water-conditioning agent or ammonium sulfate (AMS) to your spray tank before mixing the herbicide can neutralize hard-water cations and restore herbicide performance. Most lawn-and-garden retailers carry AMS packets designed for exactly this purpose. You can also test your water’s hardness with a simple strip kit; anything above about 150 parts per million of calcium carbonate equivalent is worth conditioning.

Getting Rid of Overseeded Ryegrass in Spring

In warmer climates, many bermuda lawns are overseeded with perennial ryegrass in fall to maintain green color through winter. Come spring, that ryegrass becomes an unwanted competitor as bermuda tries to break dormancy. If the ryegrass does not transition out on its own, it can smother bermuda’s spring green-up and effectively become a weed.

Research on ryegrass removal timing in overseeded bermuda found that treatments applied in March generally left too much ryegrass cover eight weeks later, while treatments applied in April, May, or early June reduced ryegrass to less than half of its original coverage.⁷ Chemical removal using herbicides like rimsulfuron was effective without causing long-term damage to bermuda recovery when timed in late spring. Aggressive mechanical methods like very low scalping can also force the transition, but they temporarily reduce overall green cover. The balance is between removing the ryegrass quickly and not setting bermuda’s recovery back in the process.

If you overseed your bermuda, the lesson is patience: wait until bermuda is showing clear signs of green-up (usually when soil temperatures hit 65°F consistently) before chemically removing the ryegrass. Push it too early and you end up with a brown lawn and no bermuda ready to fill in. Wait too long and the ryegrass competes with bermuda during its critical spring growth window.

Building a Season-Long Plan

Weed control in bermuda grass works best as a calendar-driven program rather than a react-when-you-see-them approach. A practical annual sequence for most southern and transition-zone lawns looks something like this:

• Late winter (February-March): Apply a spring pre-emergent when soil temperatures approach 55°F at a four-inch depth. This targets crabgrass, goosegrass, and other summer annual weeds before they germinate.
• Mid-spring (April-May): Follow up with a second pre-emergent application or a combination product that includes early post-emergent control. Spot-treat any broadleaf weeds with a three-way herbicide while temperatures are still moderate.
• Summer (June-August): Focus on cultural practices. Mow at the proper height, irrigate to keep bermuda dense, and spot-treat any breakthrough weeds during cooler morning hours. Avoid blanket herbicide applications in extreme heat.
• Early fall (September-October): Apply a fall pre-emergent before Poa annua and winter annual broadleaf weeds germinate. Soil temperature benchmarks for Poa annua emergence are around 66-70°F.
• Late fall and winter: Bermuda goes dormant in most regions. Spot-treat winter broadleaf weeds if needed, but avoid heavy herbicide use on dormant turf.

Fertility ties into this plan directly. Bermuda grass is a heavy nitrogen feeder, and adequately fertilized bermuda grows thicker and recovers faster from both weed competition and herbicide stress. Applying nitrogen during bermuda’s active growth months (roughly May through September in most areas) at a rate of about half a pound to one pound of actual nitrogen per thousand square feet per month keeps the turf competitive. Under-fertilized bermuda is thin bermuda, and thin bermuda is weedy bermuda.

When Non-Selective Herbicides Make Sense

Sometimes the fastest path to a weed-free bermuda lawn involves temporarily killing everything in a problem area and letting bermuda reclaim it. Glyphosate, the active ingredient in many non-selective herbicides, kills virtually all actively growing plants. In bermuda lawns, this approach works for a few specific situations: patches of dallisgrass or nutsedge that resist selective herbicides, areas overtaken by bermuda’s own weedy cousin (common bermuda invading a hybrid bermuda lawn), or spots where weed pressure is so severe that selective treatments would require a dozen applications.

The technique is straightforward. Spot-spray the affected area with glyphosate using a shield or careful hand-sprayer to limit overspray. The treated area will brown out within a week or two. Once the weeds are dead, bermuda’s stolons and rhizomes from surrounding healthy turf will begin creeping into the bare patch. In warm weather with adequate water and fertilizer, bermuda can fill a small bare area in a matter of weeks. Larger areas may need plugging or sprigging to speed recovery.

One caution: glyphosate will injure dormant bermuda less than actively growing bermuda. Some professionals apply glyphosate to dormant bermuda lawns in winter to kill cool-season weeds like Poa annua and ryegrass without significantly damaging the bermuda. This is a higher-risk technique and timing has to be precise. The bermuda must be fully dormant, and the weeds must be actively growing for the approach to work. If bermuda has started any green-up at all, you will see damage.