Triclopyr is the most consistently effective herbicide for killing greenbrier (Smilax species), and it is the active ingredient most university extension programs recommend as a first choice. Glyphosate and metsulfuron methyl also see wide use, though greenbrier’s massive underground root system and waxy leaf surface make any single herbicide application unlikely to deliver a permanent kill. The real answer to this question involves not just which chemical to reach for, but how you apply it, when you apply it, and how many times you’re willing to come back.
Why Greenbrier Resists Herbicides So Stubbornly
Before picking a product off the shelf, it helps to understand what you’re up against. Greenbrier is not a typical weed. It’s a woody, perennial vine with a root system that can include thick rhizomes and starchy tubers buried a foot or more underground. Those tubers act like batteries, storing enough energy to send up new shoots even after the entire above-ground plant has been killed. Some Smilax species produce tubers weighing several pounds, and a single plant can develop a network of them spreading across a wide area.
The leaves also work against you. Greenbrier foliage is thick, glossy, and coated in a waxy cuticle that repels water-based sprays. Herbicide droplets bead up and roll off much the way rain rolls off a freshly waxed car. This means that without a surfactant or the right spray technique, you can drench a greenbrier vine and still not get enough chemical absorbed to do meaningful damage. Between the wax problem on top and the energy reserves below, greenbrier regularly survives treatments that would flatten most other plants.
Triclopyr Is the Top Recommendation
Triclopyr is a selective broadleaf herbicide, meaning it kills dicots and woody plants while leaving grasses largely unharmed. It’s sold under brand names like Garlon, Remedy Ultra, Crossbow (which combines triclopyr with 2,4-D), and various generic formulations. For greenbrier control, triclopyr is favored because it translocates well through the plant’s vascular system and reaches the roots more reliably than many alternatives.
Two forms of triclopyr are commonly available. Triclopyr amine (the water-soluble salt, as in Garlon 3A) is typically used for foliar sprays. Triclopyr ester (the oil-soluble form, as in Garlon 4 Ultra or Remedy Ultra) is used for both foliar sprays and basal bark treatments. The ester formulation penetrates waxy surfaces more effectively, which matters a great deal with greenbrier’s slick leaves. If you’re comparing products and can choose, the ester form generally gives better results on waxy-leaved vines.
For foliar application, triclopyr ester is usually mixed at a concentration around 2 to 4 percent in water with a non-ionic surfactant added to help the spray stick. You want thorough coverage of the foliage without runoff. Spraying to the point of dripping wastes product and increases the risk of killing non-target plants near the root zone. A fine to medium mist that coats the leaves evenly is the goal.
Glyphosate Works but Demands Patience
Glyphosate, the active ingredient in Roundup and dozens of generic products, is a non-selective herbicide that kills virtually any green plant it contacts. It can kill greenbrier, but the results are inconsistent with a single application. Glyphosate relies entirely on foliar uptake and translocation, and greenbrier’s waxy cuticle reduces how much actually gets absorbed. You’ll often see the top growth brown out within a couple of weeks, only to watch new shoots emerge from the rhizomes a month or two later.
That said, glyphosate has one major advantage: it’s cheap and widely available. If you’re managing greenbrier in a mixed landscape where you don’t mind killing surrounding grasses and broadleaves, a concentrated glyphosate solution (usually 3 to 5 percent for woody vines) applied repeatedly over two or three growing seasons can eventually exhaust the root reserves. Each application forces the plant to burn through stored energy to regrow, and eventually the tubers run out of fuel. Research on glyphosate spray application has shown that droplet size affects how well herbicide deposits on target foliage, with medium-sized droplets generally providing the best balance between coverage and drift control.1Engenharia AgrÃcola. Influence of droplet size on spray deposition and weed control using glyphosate For greenbrier specifically, adding a non-ionic surfactant or a crop oil concentrate to the tank mix helps break through that leaf wax and improves uptake considerably.
Metsulfuron Methyl and Other Chemical Options
Metsulfuron methyl (sold as Escort XP, MSM 60, and other labels) is a sulfonylurea herbicide that works well on several Smilax species and is widely used in forestry and pasture management. It’s applied at very low rates, often just a fraction of an ounce per acre, and it’s selective enough to spare most grasses. For landowners managing greenbrier in pastures or pine plantations, metsulfuron methyl is a strong option, sometimes used alone and sometimes tank-mixed with triclopyr for broader activity.
A few other herbicides show up in greenbrier management recommendations:
- 2,4-D: One of the oldest broadleaf herbicides available. It can cause top-kill on greenbrier but rarely reaches the roots effectively. Most useful as part of a combination product like Crossbow (2,4-D plus triclopyr), where the triclopyr does the heavy lifting on the woody tissue.
- Dicamba: Sometimes combined with 2,4-D for brush control. Similar limitations to 2,4-D when used alone on greenbrier, but can improve results in tank mixes. Be aware that dicamba is volatile and prone to off-target drift damage, especially in warm weather.
- Imazapyr: A powerful, long-lasting herbicide used mainly in forestry and right-of-way management (sold as Arsenal, Chopper, and generics). Very effective on greenbrier but non-selective and persistent in the soil, so it can sterilize ground for months. Not appropriate for residential landscapes or anywhere near desirable plants.
- Fosamine: Marketed as Krenite, this herbicide prevents new growth the following spring rather than killing existing foliage outright. It’s used mainly in utility right-of-way management and is less common in retail channels. Results on greenbrier are mixed, and it requires a specific fall application window.
For most homeowners and small property managers, the practical choice comes down to triclopyr ester (best single-product option), glyphosate (cheapest and most available, but slower), or metsulfuron methyl (excellent in open pasture or timber settings). The others are more specialized.
Application Methods That Make the Difference
Choosing the right herbicide matters less than most people think if the application method is wrong. Greenbrier’s growth habit and root system demand specific techniques.
Foliar Spray
This is the most common approach: mix your herbicide in a pump sprayer or backpack sprayer and coat the leaves. For greenbrier, foliar spray works best when the vine is actively growing and has plenty of leaf area to absorb the chemical. Late spring through midsummer is the ideal window for foliar applications. A surfactant is not optional here. Without one, too much spray rolls off the waxy leaves. Crop oil concentrate at about 1 percent of spray volume tends to outperform cheaper non-ionic surfactants on greenbrier because the oil helps dissolve the leaf wax.
Coverage quality outweighs volume. Drenching the plant is less effective than a uniform coating, and research on spray deposition confirms that medium-sized droplets tend to stick better to foliage than very fine or very coarse ones.1Engenharia AgrÃcola. Influence of droplet size on spray deposition and weed control using glyphosate Most pump sprayers with an adjustable nozzle can produce an appropriate cone pattern if you keep the nozzle about 18 to 24 inches from the foliage.
Cut-Stump Treatment
For greenbrier vines with thick, woody stems, cutting the vine at ground level and immediately painting the cut surface with concentrated herbicide can deliver chemical directly into the vascular system. Triclopyr ester (usually at 25 to 50 percent concentration in a basal oil carrier) or a concentrated glyphosate solution (50 percent or higher) applied within minutes of cutting gives the best uptake. The cut surface dries and seals quickly, so waiting even 15 to 20 minutes can reduce effectiveness sharply.
Cut-stump treatment has an advantage over foliar spray in that it bypasses the waxy leaf barrier entirely. The downside is that greenbrier often grows in dense tangles with many thin stems rather than a few thick ones, making individual stem treatment tedious. In practice, most people use cut-stump treatment on the thickest, oldest canes and rely on foliar spray for the smaller regrowth.
The Cut-and-Spray Combination
Many experienced land managers use a two-step method: cut or mow the greenbrier back hard, wait for regrowth, and then spray the fresh new leaves with herbicide. Young, tender regrowth leaves have a thinner wax layer and absorb herbicide much more readily than mature foliage. This approach is especially useful in situations where the greenbrier has climbed high into tree canopies and the foliage is out of reach of a sprayer. Cutting it back forces new growth at ground level where you can spray it effectively.
The timing gap matters. You want the new shoots to have developed several fully expanded leaves before spraying, so the plant has invested energy in growth but hasn’t yet rebuilt its wax defenses. That usually means waiting four to six weeks after cutting.
When to Spray for Maximum Effect
Timing can make or break a greenbrier treatment. The plant’s physiology shifts through the growing season in ways that affect how much herbicide reaches the roots.
In spring and early summer, the plant is pushing stored energy upward to produce new shoots and leaves. The flow of sugars is outward from the roots, which means herbicide applied to the leaves faces an uphill battle against the plant’s own transport direction. You can still get a good foliar kill during this period, but translocation to the tubers is limited.
Late summer through early fall is generally the sweet spot. By this point, the plant is photosynthesizing at full capacity and beginning to move sugars back down into the roots and tubers to store energy for winter. Herbicide applied to the foliage hitchhikes on this downward flow and reaches the underground parts more effectively. Most extension recommendations for greenbrier call for foliar applications in August or September, depending on your climate zone.
Fall applications with triclopyr ester are particularly effective because the cooler temperatures reduce the volatility of the ester formulation (less drift risk) while the plant is still actively translocating. Once the leaves start to yellow and drop, the window closes. Spraying greenbrier after it begins going dormant is largely wasted effort.
Expect to Treat More Than Once
One of the biggest mistakes people make with greenbrier is treating once, seeing the top growth die, and assuming the problem is solved. With that underground network of rhizomes and tubers, a single application rarely kills the entire plant. Even a well-timed triclopyr application at the right concentration with the right surfactant will sometimes leave viable tubers that send up new growth the following spring.
A realistic plan involves at least two growing seasons of treatment. Apply your herbicide of choice in late summer of the first year, monitor the area the following spring and summer for regrowth, and treat any new shoots promptly. By the second or third treatment, the stored energy in the roots has usually been depleted enough that regrowth slows and eventually stops. Landowners who combine an initial mechanical clearing with follow-up herbicide treatments tend to achieve the fastest results.
For large infestations, some property managers adopt a rotational approach: divide the area into sections, treat one section per year, and circle back to the first section in subsequent years to catch any regrowth. This spreads the cost and labor while still making steady progress.
Protecting Desirable Plants Nearby
Greenbrier rarely grows in isolation. It climbs trees, tangles through shrubs, and weaves through gardens, which means that spraying it inevitably risks hitting something you want to keep. The choice of herbicide directly affects collateral damage.
Triclopyr and metsulfuron methyl are selective for broadleaf plants, so grasses growing underneath a greenbrier thicket will generally survive a directed spray. However, any desirable broadleaf plants, including garden perennials, ornamental shrubs, and hardwood trees, are vulnerable. Take care to spray only the greenbrier foliage and avoid contacting the leaves or green bark of anything you want to preserve. A shield made from a piece of cardboard or plastic held between the greenbrier and a nearby desirable plant works well for targeted applications.
Glyphosate will kill any green plant it contacts, so it requires even more caution. On the other hand, glyphosate binds tightly to soil particles and has no meaningful soil activity, so it won’t damage plants through root uptake after it hits the ground. Triclopyr ester also has relatively low soil persistence under most conditions, breaking down over weeks to a few months. Imazapyr, by contrast, can persist for many months and move through soil, making it a poor choice anywhere near desirable vegetation.
Greenbrier Species Vary in Toughness
There are roughly 20 species of Smilax native to North America, and they don’t all respond identically to herbicides. Common greenbrier (Smilax rotundifolia), which is the most widespread species in the eastern United States, is moderately responsive to triclopyr. Catbrier (Smilax bona-nox), with its notably aggressive thorns and tough leaves, tends to be harder to kill and often requires the higher end of recommended concentration ranges. Laurel greenbrier (Smilax laurifolia), an evergreen species found in the Southeast, can be particularly tenacious because it retains foliage year-round and builds up especially large tuber reserves in wet soils.
If you’re unsure which species you’re dealing with, the practical advice doesn’t change much: use triclopyr ester with a surfactant, spray in late summer, plan for retreatment. But knowing your species helps calibrate expectations. Catbrier and laurel greenbrier may take an extra season of follow-up compared to common greenbrier or the smaller, less aggressive species like Smilax glauca.
Non-Chemical Methods as Complements
Herbicide alone is one approach, but combining it with physical and cultural methods speeds things up. Repeated mowing or brush-cutting depletes root reserves over time, even without chemicals, though it’s slow. Mowing every four to six weeks throughout the growing season for two or three years can exhaust the tubers, but most people run out of patience before the greenbrier runs out of energy.
Goats are surprisingly effective greenbrier browsers. They eat the young shoots, leaves, and even the tough stems, and repeated browsing over a couple of seasons can significantly weaken an infestation. Targeted goat grazing has become a legitimate vegetation management tool on larger properties and is sometimes combined with follow-up herbicide application on any regrowth the goats miss. If you have access to livestock or can hire a goat-grazing service, it’s worth considering for dense infestations where spraying is impractical.
Digging out tubers by hand works for small, isolated patches, but it’s brutal labor. The tubers can be deep, and any fragment of rhizome left behind will resprout. For a single vine growing up a garden fence, excavation can be a permanent fix. For a patch covering a quarter acre of woods, it’s not realistic.
Prescribed fire is used in some forestry contexts to manage greenbrier. A single burn typically causes vigorous resprouting, but repeated burns on a two- to three-year cycle, especially when combined with an herbicide application to the regrowth after a burn, can provide long-term suppression. Fire alone won’t eliminate greenbrier, but it exposes regrowth to easy foliar spray access and resets the clock on the plant’s energy reserves.