Killing Smilax, the thorny vine most people call greenbrier or catbrier, demands a sustained attack on its underground root system. Cutting the vine at the surface barely slows it down, because the real plant lives below ground in a network of tough, starchy rhizomes that store enough energy to send up new shoots for years. The only reliable strategies combine physical removal or repeated cutting with well-timed herbicide applications, and even then the process usually takes more than one season.
Why Greenbrier Keeps Coming Back
Before you spend a weekend hacking at vines, it helps to understand what you’re actually fighting. Smilax species grow from a specialized underground stem called a rhizophore, which is brown, knotty, and can be either slender or swollen into a hard tuber depending on the species. These structures sit surprisingly close to the surface, typically in the top 10 to 15 centimeters of soil, but they are dense with stored starch and packed with dormant buds that can sprout into entirely new stems. The plant also spreads clonally, meaning what looks like a dozen separate vines across your property may be one interconnected organism sharing resources through a common root network.1The Journal of the Torrey Botanical Society. New approaches to underground systems in Brazilian Smilax species (Smilacaceae)
This underground design is the core of the problem. When you cut a stem, you remove the part of the plant that is photosynthesizing and sending energy downward, but the rhizome still holds a substantial carbohydrate reserve. It responds to the loss by activating one or more of those dormant buds, and a new shoot appears within weeks. If you only cut once and walk away, the vine replaces itself with no meaningful setback. To actually kill the plant, you need to either physically remove the rhizome, chemically poison it, or exhaust its energy reserves through repeated defoliation over time.
Digging Out the Roots
For a small infestation, or a single vine climbing a prized tree, physical removal is the most direct approach. Because Smilax rhizomes tend to grow in the upper few inches of soil, they are reachable with a sturdy shovel or a mattock. The challenge is completeness. Every fragment of rhizome you leave behind has the potential to regenerate. Tuberous species are the worst offenders here: a single hard tuber the size of a golf ball, left in the ground, can push out a new vine.
Start by cutting the above-ground vine at the base and pulling as much of it down as you can. Then dig outward from the base, following the rhizome laterally. Work carefully around other plants’ roots if you’re in a garden bed. Expect the rhizome to branch and to change direction. In loose or sandy soils, this can be straightforward. In clay or rocky ground, it becomes genuinely exhausting labor. For anything more than a few square feet of infestation, digging alone is impractical, and combining it with herbicide treatment on the cut stumps makes far more sense.
Herbicide Methods That Actually Reach the Roots
Chemical control is the most effective tool for established greenbrier, but the method of application matters as much as the product itself. A casual spray on the leaves of a mature vine will often fail because Smilax has thick, waxy, almost leathery leaves that repel liquid. You need either the right surfactant, the right timing, or a different delivery route.
Cut-Stump Treatment
This is the highest-confidence method for individual vines or small clusters. Cut the vine as close to the ground as possible, then immediately apply a concentrated herbicide solution directly to the freshly cut surface. “Immediately” matters here: the plant’s vascular tissue begins to seal within minutes of being cut, and the herbicide needs to travel down through the stem into the rhizome while the pathway is still open. Many experienced land managers carry a squeeze bottle or a foam paintbrush and treat each stump within 30 seconds of cutting.
Triclopyr is the herbicide most commonly recommended for woody vine cut-stump work. In its ester formulation, it penetrates bark and cut surfaces readily and translocates down to the roots. Glyphosate also works on cut stumps, though it tends to be less selective, meaning any root systems intertwined with the Smilax rhizome may also be damaged. For cut-stump applications, the herbicide is typically used at a much higher concentration than for foliar spraying. Products sold for “brush control” or “stump killer” at garden centers usually contain triclopyr at the right strength for this purpose.
One practical advantage of cut-stump treatment is that it works in nearly any season, because you’re bypassing the leaf surface entirely and delivering herbicide straight to the vascular system. Late summer through fall, when the plant is naturally pulling energy downward into storage, gives the best translocation to the roots. But winter applications also work reasonably well as long as temperatures are above freezing.
Foliar Spray
For large infestations where cutting every vine is impractical, foliar spraying is the alternative. The goal is to coat enough leaf surface that the plant absorbs a lethal dose and moves it to the roots. This is harder than it sounds with Smilax because of the waxy leaf cuticle. Adding a non-ionic surfactant to the spray mix improves leaf uptake considerably. Without a surfactant, the herbicide beads up and rolls off.
Timing is critical for foliar applications. The best window is late summer through early fall, when the vine is actively photosynthesizing and transporting sugars down to the rhizome for winter storage. By spraying during this period, the herbicide essentially hitchhikes on the plant’s own downward flow of nutrients and reaches the roots more effectively. Spraying in spring, when the plant is pushing energy upward into new growth, tends to kill the foliage without delivering enough chemical to the rhizome. The vine looks dead for a few weeks, then resprouts.
Glyphosate and triclopyr are both used as foliar sprays for greenbrier. Triclopyr has the advantage of being selective against broadleaf and woody plants while leaving grasses unharmed, which is useful if your greenbrier grows among lawn or pasture grasses. Glyphosate kills grasses too, so it works better in situations where you’re clearing an area entirely or can apply it carefully with a targeted sprayer. For either product, use the rate specified on the label for “woody vines” or “brush,” not the lower rate meant for annual weeds.
Basal Bark Treatment
A third option that works well on greenbrier is basal bark application. You mix a triclopyr ester product with an oil-based carrier (often a horticultural oil or diesel, though many labels now recommend specific basal oil carriers) and paint or spray the mixture onto the lower 12 to 18 inches of the vine’s stem. The oil carries the herbicide through the bark and into the vascular tissue. This method works year-round, doesn’t require cutting, and is well-suited to vines growing up into trees where you can’t easily reach the foliage with a sprayer. The downside is that it uses more herbicide per vine than a cut-stump approach and is slower to show results.
Repeated Cutting Without Herbicide
If you’d rather avoid chemicals entirely, you can kill greenbrier through persistence alone, but you need to understand the timeline. The strategy is to cut every stem as soon as it produces new leaves, forcing the plant to draw on its root reserves to regrow. Eventually the reserves run out and the rhizome dies. This works, in theory, because the plant needs photosynthesis to replenish the starch it spends on each regrowth cycle. By never letting the new foliage mature, you prevent the recharge.
In practice, this takes a long time. Smilax rhizomes store a lot of energy, and the plant is adapted to resprouting after fire, browsing, and storm damage. Expect to cut regrowth every two to four weeks during the growing season, and to keep it up for at least two full growing seasons. Missing even a few weeks gives the vine enough time to photosynthesize and send energy back down. For a large area, this level of attention is exhausting. For a single vine in a flower bed, it’s doable. A string trimmer or hedge shears work fine for the repeated cuts; you don’t need to re-dig each time, just remove all green tissue at or near the soil surface.
Mowing serves the same function on a larger scale. Regular mowing through the growing season, set low enough to clip emerging greenbrier shoots, will gradually suppress the vine in pastures and open fields. The key word is “gradually.” Research on similar resprouting plants suggests that it can take multiple seasons of consistent mowing to fully deplete the underground reserves, and any interruption lets the vine recover ground.
Goats and Other Browsing Animals
Goats are often recommended as a natural greenbrier control, and they do eat it readily, thorns and all. But “eating it” and “killing it” are different things. A three-year study that used intensive mob browsing with goats on greenbrier-infested pastureland found that greenbrier as a proportion of total vegetation did not decline over the study period. The goats browsed it aggressively, but the root system kept pushing up new growth. In paddocks that were not browsed at all, greenbrier actually increased, so the goats clearly suppressed expansion. They just couldn’t eradicate what was already established.2Livestock Research for Rural Development. Greenbriar suppression with goat mob browsing
This makes goats a maintenance tool, not a removal tool. If you’re managing a large pasture and want to keep greenbrier from taking over, rotating goats through can hold the line. If you want a patch of greenbrier gone, goats alone won’t get you there. Combining browsing with targeted cut-stump herbicide treatment on the most established root crowns is a more realistic approach for elimination.
Fire as a Control Method
Prescribed burning is used in forestry and land management across the southeastern United States, where Smilax species are most abundant. Fire kills the above-ground portion of the vine effectively and can be useful for clearing dense thickets. However, greenbrier is well adapted to fire. The rhizome system, insulated by even a few centimeters of soil, typically survives and resprouts vigorously within weeks. In fire-adapted ecosystems, Smilax is one of the first plants to return after a burn.
Repeated burning on a schedule that doesn’t allow the vine to recover fully between fires can weaken it over time, much like repeated mowing. But a single burn is essentially just a very thorough above-ground cut. If fire is part of your land management plan, the most effective greenbrier strategy is to burn first to clear the above-ground growth, then follow up with herbicide treatment on the resprouts when they’re young, actively growing, and easier to spray. The fresh, tender post-fire leaves also lack the thick waxy cuticle of mature foliage, which means they absorb foliar herbicide more readily.
Timing Your Approach for Best Results
Across all methods, the seasonal timing of your main attack matters. Greenbrier follows a predictable annual cycle. In spring, the rhizome spends stored energy to push up new shoots. Through summer, the vine photosynthesizes and begins replenishing those reserves. In late summer and fall, the plant actively translocates sugars and starch downward into the rhizome for winter storage. This is why late-season herbicide application works best for foliar sprays: the plant’s own plumbing carries the chemical to the roots.
For physical methods like digging, late fall or winter is often easiest. The soil may be softer after autumn rains, the vine is dormant or semi-dormant, and you can see the root crowns more clearly without dense foliage in the way. For cut-stump treatment, you have the widest window because the herbicide enters through the cut surface rather than the leaves, though fall applications still give a slight edge in translocation.
The worst time to start a greenbrier control campaign is early spring, when the plant has a full tank of root reserves and is primed to grow. Cutting or spraying at that time often just stimulates more vigorous regrowth. If you’re inheriting a greenbrier problem on a new property and your first impulse is to hack it back in April, hold off on any chemical work until at least mid-summer. Clear what you need to for access and safety, but save the herbicide applications for when they’ll do the most root-level damage.
Preventing Reestablishment
Once you’ve killed a stand of greenbrier, the site remains vulnerable to reinvasion. Smilax produces small berries that birds eat and distribute widely, and seeds can remain viable in the soil for years. A cleared area with bare or disturbed soil is an invitation for new seedlings.
The best defense is establishing dense competing vegetation as quickly as possible. In a garden setting, heavy mulch and dense plantings help shade out any greenbrier seedlings before they can develop a significant root system. In a pasture or forest understory, encouraging a thick grass or ground cover layer makes it harder for Smilax to gain a foothold. Young greenbrier seedlings, before they’ve built a substantial rhizome, are relatively easy to pull by hand or kill with a single herbicide application. The key is catching them in the first year, before the underground storage system develops. A small greenbrier seedling has a root the size of a pencil eraser. A three-year-old plant has a woody tuber that laughs at your shovel. Vigilance in the first two years after clearing pays dividends for a decade.
When a Professional Makes Sense
Most homeowners with a few greenbrier vines can handle the job with a pruning saw, a bottle of triclopyr concentrate, and some patience. But there are situations where calling a professional vegetation management company or a licensed pesticide applicator is worth the cost. Dense, multi-acre infestations in wooded areas are extremely labor-intensive to treat vine by vine, and a professional crew with backpack sprayers can cover ground far more efficiently. Properties near wetlands, streams, or other sensitive areas may have herbicide restrictions that require a licensed applicator to navigate. And some Smilax species, particularly the evergreen laurel-leaf greenbrier common in the Deep South, form such impenetrable thickets that mechanical clearing with a forestry mulcher is the only realistic first step before any chemical follow-up.
Expect to pay for at least two visits: an initial treatment and a follow-up the next growing season to catch resprouts. Any company that promises single-visit eradication of established greenbrier either doesn’t understand the plant or is telling you what you want to hear. The rhizome system is too resilient for one-and-done approaches, no matter what product is used.