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Controlling buckthorn: the who, what, where, when and how

By Matt Russell, Extension forest resources specialist, Gary Wyatt, Extension educator and Claire LaCanne, Extension educator

Leaves of buckthorn. Photo: Chris Evans, forestryimages.org
Buckthorn is one of Minnesota’s most damaging invasive plants. Landowners should be concerned if buckthorn is present in their woodlands because it is an aggressive invasive plant that outcompetes native vegetation and degrades wildlife habitat. Soybean growers should be concerned if buckhorn is present in nearby wooded areas because it serves as the overwintering host plant for soybean aphid eggs and the crown rust fungus.

Understanding the basics of buckthorn biology will help you to control its spread so that you have a healthy woodland and crop field. Despite the invasive nature of buckthorn, many landowners have had success in controlling it, but only after choosing the appropriate management techniques along with consistent follow-up treatments.

What is buckthorn?

Buckthorn may refer to one of two different species found in Minnesota: Common (or European) buckthorn (Rhamnus cathartica) or glossy buckthorn (Frangula alnus). The species arrived in Minnesota from Europe in the 1850’s and was planted as an ornamental plant typically used in hedges. Today, both species are listed as restricted noxious weeds in Minnesota. The sale, transport, or movement of buckthorn is prohibited statewide.

Buckthorn is a shrub or small tree that can reach 25 feet tall and takes an oval form. They are noticeable in woodlands because they can form dense thickets where few other plant species will exist in the understory.

The key identifiable feature of buckthorn is the “buck hoof print” that can be seen at the end of the twig. This hoof print is formed by two terminal buds and a thorn going down the middle. Buckthorn leaves are some of the first leaves to appear in the spring and the last to drop their leaves in the fall, a common trait among many woody invasive plants.

Watch this video from Extension Educator Angie Gupta for more tips on how to identify buckthorn:


Where is buckthorn in Minnesota?

Common buckthorn is found on dry and moist sites, while glossy buckthorn is typically found on wet sites. Both species can grow either in full sun or deep shade.

Common buckthorn is widely distributed across central and southeastern Minnesota, with northern populations extending along the North Shore of Lake Superior and into northwestern Minnesota (Figure 1, left).

Glossy buckthorn has a narrower distribution compared to common buckthorn. It is abundant in the central and eastern portions of Minnesota (Figure 2, right):
Figure 1: Current distribution of common buckthorn. Maps available at theData Repository of the University of Minnesota
Figure 2: Current distribution of glossy buckthorn. Maps available at the Data Repository of the University of Minnesota

Who is managing buckthorn?

Buckthorn is currently being managed by woodland owners, crop growers, and natural resource professionals. In a 2018 survey on invasive plants across Minnesota, common buckthorn was the most frequently reported invasive plant for both private landowners and public land professionals working across forest and agricultural settings.

In a recent online workshop on invasive plants offered by UMN Extension and the MN Department of Agriculture, agricultural and natural resource professionals were presented with a hypothetical budget of one million dollars to spend on invasive plant management. Professionals indicated they would spend over $400,000, or 40% of their entire budget, to control the two buckthorn species alone. This is a reflection of how professionals are eager to minimize the damage and control the spread of buckthorn.

Many organizations may be able to assist in buckthorn management. Your local Soil and Water Conservation District (SWCD) office may be aware of cost share opportunities through programs in the Natural Resources Conservation Service. Landowners with woodlands may be eligible for state-level cost-share assistance through the MN Department of Natural Resources.

How do you control buckthorn?

A number of chemical and non-chemical control methods are available for buckthorn. When controlling buckthorn, female plants should be targeted first. This is because female buckthorn plants produce the seeds from berries that are widely dispersed by birds and other wildlife.

Non-chemical treatments

In areas where buckthorn is not yet dense, small seedlings and trees can be pulled by hand or with tools such as a weed wrench.

In areas where buckthorn has formed a dense understory, mowing may be one option to reduce vegetation and evaluate re-growth. After mowing, resprouts and new growth will occur, so monitor the area and conduct follow up treatments as needed. Combining mowing with chemical treatments can also be effective.

Controlled burning may be an option on grassland or savanna sites. Landowners have reported moderate success with using burning to control buckthorn. Burning will need to occur every two to three years to be an effective management technique.

The use of goats and other livestock has become more popular in recent years for controlling buckthorn. Goats will graze buckthorn and other vegetation, which can help control the invasive plant. Research on using goats to control buckthorn is still emerging that investigates the long-term effects of grazing on buckthorn populations and what vegetation is replacing it.

Large diameter buckthorn stems can be cut at the stump with a chainsaw, brush cutter or other hand tool. After cutting, cover the stump with a tin can or black plastic to prevent future sprouting.

Chemical treatments

Following a cut stump treatment with brush herbicide can be effective for larger-diameter buckthorn stems. Herbicides containing glyphosate or triclopyr are recommended for buckthorn control. Apply the herbicide on the stump with a paintbrush, dauber, or low volume sprayer by covering an inch in from the edge of the outer bark. The center of the stump does not need to be treated.

Glyphosate is a non-selective herbicide, while triclopyr has a water- or oil-based formulation. The oil-based formulation works well for cut stump treatments.

Herbicide can also be applied directly to the bark using a basal bark treatment. This treatment works well for trees up to 5 inches in diameter. From the ground level up to 18 inches above the ground, wet the area with a low-volume sprayer.

Foliar applications are effective for smaller buckthorn plants. Spray buckthorn leaves until wet. The water-based formulation of triclopyr works well for foliar applications.

Follow label directions when using herbicides, wear recommended protective clothing, and avoid contact with non-target plants. Consider re-establishing native plants in areas previously dominated by buckthorn.

Cost and effectiveness of buckthorn treatments

In a 2018 survey on invasive plant management in Minnesota, public land professionals reported average costs per acre for both mechanical removal (e.g., by mowing) and herbicide treatments of buckthorn to be around $200 per acre. Manual removal (e.g., by hand pulling) of buckthorn was reported to cost over $600 per acre.

In that same survey, both public land professionals and private landowners reported on the effectiveness of different treatments for controlling common buckthorn:
  • 72% of respondents said that herbicide treatments were extremely or very effective for controlling buckthorn.
  • 50% of respondents said that manual removal treatments were extremely or very effective for controlling buckthorn. 
  • 23% of respondents said that mechanical removal treatments were extremely or very effective for controlling buckthorn. 

When is the best time of year to control buckthorn?

Buckthorn control treatments can occur at any point in the year, but a few specific times tend to be optimal for the best results. Late summer and throughout the fall is the best time to cut and chemically treat buckthorn stumps. Foliar applications of herbicide on buckthorn are well suited in October after native foliage has gone dormant.

If using chemical treatments in the fall or winter, follow herbicide label instructions for the appropriate temperatures in which to apply chemicals. Oil-based herbicides are usually best for fall and winter applications.

Conclusion

Buckthorn is one of Minnesota’s most ecologically and economically damaging invasive plants. As a noxious weed that outcompetes native vegetation in woodlands and serves as an overwinter host for soybean aphid, controlling buckthorn can provide a healthier woodland and improved soybean yields. A variety of chemical and non-chemical treatments are available to control buckthorn, each with varying effectiveness and costs.

The right treatments will depend on the severity of the buckthorn infestation and time and resources available. Buckthorn seeds can persist in the soil for 2-3 years, so monitor the affected area annually after initial treatment. Conduct follow-up treatments if needed.

To learn more, watch the video below to find out how two soybean growers are controlling buckthorn to manage soybean aphid:


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Comments

  1. Several years ago (6-7) I hired a neighbor with an excavator to dig out the buckthorn which was quite a problem in some areas of my woods. We piled the plants with intention of burning them after a year of drying out. However, I never did burn the piles and to date the "weed" remains under complete control. I completed the removal under ate EQIP program which did not entirely pay the expense, but well reduced my out of pocket cost, with a lot less nasty scratches
    and no chemicals. Evans Tree Farm, Potsdam, New York

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    1. It's great to hear you were able to control the buckthorn! Thanks for sharing your experiences. Burning is an option for getting rid of buckthorn, so long as it aligns with local burning laws.

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    2. Can someone tell me more about the EQIP program? I'm not aware and we have 4 acres with buckthorn we'd like to better manage.

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  2. Hi Matt, What signs indicate it is too late to spray the leaves in fall? I suspect there was no window after native dormancy this year but want to make sure.

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    1. Billy: If foliage application is used for buckthorn, it may be too late in the season to use it. The plant needs to be actively growing and we often recommend foliage application in the spring. Gary Wyatt mentioned that next week if temperatures are in the 50's degree, a foliar application might work. Make sure the product is labeled for a foliar application and follow directions for a foliar application exactly.

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  3. I was hoping you would suggest what comes next after removal, what is effective in planting and growing in the cleared soil so that the Buckthorn has something to compete with until erradicated.

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    1. This is a good question. I would also be interested in knowing what to plant on our forest edge area once cleared of buckthorn. Does native plant effectively compete?

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  4. When treating buckthorn trees, be aware that there are male and female trees. The female trees bear purplish/black fruit that the birds eat and spread. Therefore, landowners may want to target and identify the female trees first. Cut stump and treat is the best method for large tree control. Cut the stump and treat the bark layer around the stump soon (within 30 minutes) with a brush herbicide with the active ingredient, triclopyr. The female trees with berries should be removed and piled and covered with a tarp or plastic or burned. If left uncovered or in the woods, birds can still pick the seeds and spread in the area.

    What to plant? There is an interesting study that may be concluding in 2022 called "Cover it up". Looking at native plants and trees/shrubs that could be planted to possibly shade out or compete with buckthorn. The website seed mixes is: https://coveritup.umn.edu/seed-mix
    Search around the website for more information or email coveritup@umn.edu for more information and the final reports. Generally, if you remove buckthorn there should be a native seed bank of plants that will emerge in that area. Remember, there may also be buckthorn seeds in the area so it is very important to monitor buckthorn controlled sites for buckthorn regrowth and further treatments (months and years). You could consider planting native shrubs along the forest edge for wildlife and human consumption, like hazelnuts, Juneberry, black chokeberry, elderberry, etc.
    https://extension.umn.edu/agroforestry/growing-edible-fruits-and-nuts
    Good Luck!

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  5. What would you recommend for hunters who prefer to leave their property undisturbed during the hunting season. Would controlling a large infestation over many acres with herbicide be effective in August or January for northern climates?

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    1. Kevin, you are right, hunters will not want to be in the woods and treat buckthorn plants before or during the deer hunting season in the fall. Pulling small plants and stump cut treating larger buckthorn trees can be done any time of year. Use a brush herbicide with an active ingredient of "triclopyr". The MN DNR has 90% success in treating buckthorn in the winter months. Remember to treat bark rim of the cut completely all around the stump. You may want to avoid the spring freeze/thaw period due to sap movement from the roots not down to the roots. (February/March?) August and January would be fine months to control buckthorn. I am glad you are interested in improving your native woodland habitat!

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  6. I live on a suburban lot in the Twin Cities, and have lived here for 44 years. I have never had buckthorn bushes on my property, but I have several dozen small (1 - 2 in.) buckthorn shoots in my front and back lawns. After pulling out many shoots I realize that they have an extensive root system. I read that a shoot will not grow back if pulled out. But given that root system, I have to believe that new shoots are destined to sprout over time. What can I do to eradicate the root system and keep shoots from sprouting in the future? I am currently pulling out sprouts with as much root as possible, when the soil is damp.

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    1. Buckthorn does not have underground stems. If you pull the plant - which comes out with most of the root system - it will NOT regrow! Pulling buckthorn does control buckthorn.

      Larger buckthorns can be cut but the stumps need to be treated with a brush herbicide. For more information, visit https://extension.umn.edu/planting-and-growing-guides/woody-vegetation-control
      Good luck!

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  7. I make tinctures out of invasive buckthorn and walking sticks.
    Spay the stump left, pretty easy to identify but they need a year to cure.

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    1. Keep up the good work of controlling Buckthorn and re-purposing the wood into walking sticks - Great!

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  8. I have 40 acres with several patches of buckthorn throughout. Many 5 ft plus. I am considering cutting as much as possible with a brush hog mower, then follow up in summer with triclopyr or glyphosate to treat shoots. Hoping to cover more/larger areas faster that way. I cut and stump treat smaller areas. Just don't have enough hours in the day.

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    1. Jay, if you foliar spray a brush herbicide after the buckthorn stems have grown new (multiple) stems from each stump, you will also kill any other broadleaf plant and tree recovering from this bush hog mowing treatment. Spot spraying the buckthorn stumps would help in just killing buckthorn stems. If this area is mostly buckthorn and no or minimal desirable plants your method may be the best way to manage buckthorn the first time. This site needs to be monitored closely after treatment for regrowth.

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