Thorn vines, such as greenbrier, wild blackberry, and multiflora rose, are aggressive woody plants notorious for their robust root systems that make eradication difficult. These vines rapidly grow and can quickly choke out desirable vegetation, requiring a strategic, multi-step approach for permanent removal. Addressing only the visible growth is ineffective because the underground structure holds significant energy reserves, allowing the plant to quickly regrow. A successful strategy must combine physical removal of the above-ground mass with a targeted method to eliminate the deep-seated root structure.
Identifying the Vine and Initial Clearance
Accurately identifying the thorny vine is the first step, as this helps determine the most effective control method. Common culprits include the native Smilax species (greenbrier) and invasive species like multiflora rose, which forms dense, thorny thickets. Before beginning any work, wearing thick gloves, long sleeves, and eye protection is essential to prevent injury from thorns and sap.
The primary physical task is removing the bulk of the above-ground material to gain access to the root crown. Use pruning shears or a saw to sever the main stems close to the ground, leaving a stump of three to five inches. If the vines are climbing a structure, cut them at the base and leave the upper portions to die naturally, since pulling them down can cause damage. Cutting the stems stops photosynthesis but does not kill the plant, which will quickly attempt to resprout from the roots.
Applying Systemic Chemical Treatments
The most efficient method for killing the entire root system of a persistent woody vine involves the targeted use of systemic herbicides. Systemic chemicals are absorbed by the plant and translocated through its vascular system down to the roots, where they disrupt growth processes. The “cut-stump” method is the most environmentally precise application, minimizing chemical contact with surrounding desirable plants.
This technique requires applying a concentrated herbicide directly to the freshly cut surface of the vine stump. The application should occur immediately after cutting, ideally within five minutes, because woody plants quickly seal the wound, which prevents herbicide absorption. The living tissue, or sapwood, is the outer ring of the stump, and this area must be thoroughly coated to ensure the chemical travels effectively to the roots.
Herbicides containing active ingredients such as glyphosate or triclopyr are effective for this method. Triclopyr is often preferred for woody plants and can be mixed with oil for better penetration. The optimal time for cut-stump treatment is late summer through fall, when the plant is naturally moving carbohydrates down to the root system for winter storage, which enhances the translocation of the herbicide. Applying concentrated herbicide ensures a lethal dose is delivered directly to the root system, preventing vigorous resprouting.
Non-Chemical Root Suppression Strategies
For those who prefer to avoid chemical treatments, intensive physical removal of the root structure is a viable, though labor-intensive, alternative. This process involves digging out the entire root crown and any extensive rhizome or tuber systems that the vine may have established. With well-established thorny vines, the root mass can be substantial, making this a physically demanding task.
Another non-chemical strategy focuses on root suppression by smothering the area to starve the roots of light and air. This method, often called sheet mulching, involves cutting the vines to the ground and then covering the entire area with a thick layer of cardboard or landscape fabric, followed by a heavy layer of organic mulch. The light-blocking barrier prevents the vine from photosynthesizing, eventually depleting the stored energy in the root system.
This smothering technique requires patience, as the barrier must remain in place for at least one to two full growing seasons to fully exhaust the root system. Solarization, which involves covering the area with clear plastic sheeting to generate lethal temperatures, is a similar but faster process. Both smothering and solarization are effective alternatives, but they require a long-term commitment and may render the area unusable for other planting during the suppression period.
Maintaining Eradication and Preventing Regrowth
Successful, long-term thorn vine control depends on consistent monitoring and the immediate management of any subsequent regrowth. It is unrealistic to expect a single treatment to permanently eradicate a deeply rooted woody vine. Vigilance must be maintained over the area for at least several growing seasons following the initial removal.
Any new sprouts that emerge must be dealt with immediately before they can rebuild the root system’s energy reserves. Small sprouts can be pulled by hand, ensuring as much of the root as possible is removed. If multiple or larger sprouts appear, a follow-up application of the cut-stump method or a spot treatment of a foliar herbicide may be necessary.
Preventing new infestations involves removing the conditions that favor vine growth and limiting seed germination. Establishing a dense, competitive ground cover of desirable plants acts as a natural deterrent by monopolizing soil resources and sunlight. Regular mulching of the area suppresses the germination of new vine seeds.