Buckthorn is becoming one of Minnesota’s most damaging invasive plants. If it is present in your woodland, it really becomes aggressive and invasive. I’ve even found it in my flower beds — no doubt spread by the birds.
The University says that it serves as the overwintering host plant for soybean aphid eggs and the crown rust fungus. It can outcompete native vegetation.
How did it get here? It arrived in Minnesota from Europe in the 1850s and was planted as an ornamental plant and used for hedges. It is now on the noxious weed list 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.
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How do we get rid of buckthorn? You need to concentrate on the female plants first as they produce seed which is disbursed by birds and other wildlife. If you don’t have a lot yet, small seedlings and trees can be pulled by hand or with tools. If possible, mowing might be an option. After mowing, re-sprouts and new growth will occur and will need follow-up treatment. Combining mowing with chemical treatment is an option.
Goats will graze buckthorn which can help control the plant. Research on that is still ongoing to see what the long-term effects of grazing will produce.
Large diameter buckthorn stems can be cut at the stump with a chainsaw or other tools and after cutting, cover the stump with a tin can or black plastic to prevent future sprouting. (Sounds like a lot of work to me.) 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.
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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.
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.
