Buckthorn is a highly invasive plant that aggressively displaces native species, creating dense thickets that severely diminish biodiversity in natural areas. Effective removal requires a sustained, multi-pronged approach because the plant is tenacious and produces abundant seeds. Eliminating buckthorn and preventing its return demands immediate action to kill established plants and persistent follow-up to manage the resulting seed bank.
Confirming Identification of Buckthorn
Properly identifying the target plant is the necessary first step, as buckthorn can be mistaken for several native shrubs. Common Buckthorn (Rhamnus cathartica) and Glossy Buckthorn (Frangula alnus) share the characteristic of retaining their leaves long after native trees have dropped theirs, often staying green late into the fall. Common Buckthorn has finely toothed leaves arranged in a sub-opposite pattern, and its twigs are often tipped with a spine or thorn. Glossy Buckthorn leaves are oval, lack teeth entirely, and are arranged alternately along the stem.
A definitive feature for both species is the inner bark, which is a vibrant orange or yellow color and is visible when the outer bark is scraped. Both produce pea-sized, dark purple to black berries that contain multiple seeds. These berries act as a strong laxative, promoting the wide dispersal of seeds by birds and mammals.
Non-Chemical Removal Techniques
Physical removal is best suited for younger buckthorn plants, especially where herbicide use is not desired. Small seedlings and plants with a stem diameter of less than three-eighths of an inch can be easily hand-pulled, particularly when the soil is moist. For slightly larger plants up to about two inches in diameter, a specialized tool like a weed wrench uses leverage to pull the entire root system out of the ground. Uprooting the plant entirely is the most effective way to prevent re-sprouting.
Cutting the buckthorn stem without follow-up treatment is generally ineffective for long-term control, as it typically causes the stump to vigorously re-sprout multiple stems, creating an even denser shrub. For large, tree-sized buckthorn, girdling can be employed by removing a strip of bark entirely around the trunk. Girdling must cut through the phloem layer just beneath the bark to stop the flow of nutrients to the roots, causing the tree to die slowly over a year or more.
Effective Herbicide Treatments
Chemical control is often necessary for established buckthorn to ensure the entire root system is killed and prevent aggressive re-sprouting. The most effective method is the cut-stump treatment, which involves cutting the trunk close to the ground and immediately applying a herbicide to the freshly cut surface. The application must be done quickly, ideally within minutes of cutting, to allow the plant to absorb the chemical before the wound seals. The herbicide must be painted or sprayed onto the outer ring of the stump (the cambium layer) responsible for transporting the chemical down to the roots.
Two chemicals are highly effective for this application: Glyphosate and Triclopyr. For Glyphosate, a product with at least a 25% active ingredient concentration is recommended for cut-stump application. Triclopyr can be used in a water-based formula at a 25% solution or as an oil-based ester formulation. The oil-based Triclopyr is often preferred because it can be applied for up to a month after the cut, and mixing it with a basal oil improves penetration.
The best time for cut-stump treatment is late fall or early winter, even after native plants have gone dormant. Buckthorn retains its green leaves longer than most other plants, meaning it is still actively drawing resources down to the roots, which helps pull the herbicide deep into the root system. For smaller buckthorn with stems less than three inches in diameter, the basal bark method is an alternative. This technique uses an oil-based Triclopyr formulation, such as a 20% solution, which is sprayed or painted onto the bark around the entire circumference of the lower 12 to 18 inches of the intact stem.
Long-Term Site Management
Killing the initial buckthorn plants is only the beginning of a successful management plan, as the soil is left with a significant seed bank. Continuous monitoring is required because new seedlings will germinate for at least two years after the parent plants are removed. Recent research suggests that nearly all new buckthorn sprouts from the seed bank appear within the first two years.
Proper disposal of the cut material is also necessary to prevent re-establishment or further seed spread. Any stems with berries should be bagged and disposed of as trash to prevent the seeds from germinating elsewhere. The cleared area should be restored by planting native species to prevent the buckthorn from reclaiming dominance. Establishing a dense cover of native grasses, sedges, or shrubs can significantly suppress buckthorn re-establishment by limiting the light available to new seedlings.