Buckthorn is a highly resilient invasive plant, known for its ability to rapidly return to an area after removal. Without follow-up control, buckthorn will come back. Here we will focus on the crucial phase that follows initial removal: preventing reinvasion and encouraging native plants to thrive.

Why Buckthorn Keeps Coming Back: The Challenge of Reinvasion

Buckthorn's success in re-establishing itself is due to several factors:

Vigorous Re-sprouting: Cut buckthorn stems, especially larger ones, can re-sprout vigorously and repeatedly if not treated.
The Soil Seedbank: Buckthorn produces large quantities of berries containing seeds. These seeds fall to the ground and can germinate in the years following removal.
New Seed Introduction: Even if you eliminate all buckthorn seeds on your property, birds and other wildlife can introduce new seeds to the site.

Historically, it was believed that buckthorn seeds could remain viable in the soil for up to six years or more. However, recent research from the University of Minnesota suggests that buckthorn seeds in the soil primarily germinate within one to two years after fruiting trees have been removed.

Most new buckthorn sprouts observed in studies appeared within the first year, with nearly all others appearing in the second year. This means that while vigilant follow-up is absolutely necessary, the period of intense management to address germinating seeds may be shorter than previously thought.

Revegetation: Using Native Plants to Suppress Buckthorn

An open prairie with native grasses and plants established to out compete buckthorn regrowth.

One of the most effective strategies for preventing buckthorn reinvasion is to quickly establish dense cover of native plants after initial removal. Native plants compete with new buckthorn seedlings and re-sprouts for essential resources like light, nutrients, and water. This competition, also known as biotic resistance, makes it harder for buckthorn to establish and grow.

Revegetation should be conducted as soon as possible after initial buckthorn management. Often, this means seeding in winter or planting in early spring. Establishing dense native vegetation while buckthorn seedlings are small and vulnerable provides the best chance at suppression.

Choosing the Right Native Plants for Your Site

The best native plants to use for revegetation depend on the conditions of your site, particularly the amount of light available:

Sites with More Light (>10% Canopy Openness): In areas like oak woodlands or savannas where more than 10% of the sky is visible through the tree canopy, dense seeding of grasses and wildflowers can be effective.

Grasses: Cool-season grasses (C3) are particularly good for initial suppression because they establish quickly and create thatch that reduces light later into the fall. Wildrye grasses (such as Canada, Virginia, and Silky wildrye) are recommended as they establish quickly, can grow densely, and are tall enough to shade buckthorn. Seeding grasses at rates of at least 60 seeds per square foot is recommended.
Wildflowers: While slower to establish, wildflowers are more shade-tolerant than grasses and can provide long-term cover, diversity, and habitat benefits. If included, they can be seeded at lower rates.

Darker Sites (Closed-Canopy Forests): In areas with less light, planting native trees and shrubs is often more effective.

Woody species compete strongly with buckthorn due to similar growth requirements.
Species that hold their leaves late into the autumn (like red elderberry), evergreen species (like balsam fir), and shade-adapted species (like sugar maple) are particularly effective because they reduce light when buckthorn relies on it for growth.
Research suggests that the abundance (density) of native tree and shrub stems is more important in suppressing buckthorn re-establishment than the specific identity of the woody species planted. Focus on establishing the greatest number of native stems possible, including encouraging naturally recruiting native volunteers.
Planting bare-root stems, plugs, or containerized plants is common. Planting should aim for sufficient density to create continuous cover within two years.
Be aware that deer browsing can significantly impact planted woody stems, so protection like fencing or caging may be necessary in areas with frequent deer activity.

Revegetation alone will likely not completely prevent buckthorn reinvasion. It works best when combined with other follow-up approaches.

There are many native plants that do well in holding off buckthorn infestations.

Ongoing Follow-Up: Managing What Remains and What Returns

Even after initial removal and revegetation, some buckthorn stems will likely persist, or new ones will sprout from seed or be brought in by wildlife. Regular monitoring and follow-up control are essential for long-term success. Plan on walking your property at least once a year to find and remove new plants. The best time to scout for buckthorn is fall and early spring when most other plants have lost their leaves.

Follow-up control options include:

Manual Removal: Pulling small seedlings by hand or using hand tools like weed wrenches for larger stems is effective for removing new plants. Minimize soil disturbance to avoid encouraging more seed germination.
Herbicide Treatment: Treating new buckthorn sprouts or small plants with herbicide can be effective. Foliar spraying can be used on seedlings or short buckthorn. Triclopyr is selective and won't harm grasses, while glyphosate is non-selective. Always follow label instructions and apply carefully to avoid desirable plants. Triclopyr foliar spray can be effective on remnant stems and resprouts without affecting revegetated grasses if applied carefully, ideally in late summer or fall when natives are dormant.
Prescribed Fire: In grassland or savanna areas with sufficient fuel (like revegetated grasses), controlled burns can be a long-term management option for controlling buckthorn seedlings. Burning may need to be done every two to three years. Note that fire is less effective on larger stems or resprouts.
Targeted Grazing: Goats can browse young buckthorn plants and open up the understory, potentially aiding native plant recovery. However, goats also eat desirable native plants, and buckthorn often re-sprouts after grazing. Grazing alone is not advisable, especially in wooded areas, and should be used in conjunction with other methods. Goats are less effective on larger buckthorn trees.

Persisting with follow-up removal for the first few years after initial management is crucial. As your revegetated native plants become established, they can help reduce the number and growth rate of new buckthorn, making follow-up easier over time.

Benefits Beyond Control

Managing buckthorn and restoring your site with native plants offers many benefits beyond simply removing the invasive species. It helps improve and diversify the native plant community, provides food and habitat for pollinators and wildlife, reduces the need for herbicides, and contributes to the overall health of Minnesota's woods, waters, and grasslands.

Staying Vigilant and Finding Support

Buckthorn management is truly a multi-year commitment. Staying vigilant and regularly scouting for new seedlings will significantly reduce your long-term workload. Don't hesitate to seek assistance if needed. Your local County Agricultural Inspector, Soil and Water Conservation District (SWCD), or DNR forester may be able to provide technical assistance, advice, or information on cost-share programs. The University of Minnesota Extension also offers valuable resources and guidance.

By combining effective initial removal with strategic revegetation and consistent follow-up, you can significantly reduce buckthorn abundance and help restore the health and biodiversity of your landscape for the long term.

Contact Us