Getting rid of common buckthorn
The recent beautiful fall weekend found me outside, working in my garden and marveling at the view from my hilltop. The maple leaves are brilliant orange and red, and the birches and aspen are golden yellow. Most of the native trees and shrubs found in woodlots, fencerows, windbreaks and forest edges are in the process of losing their leaves. There is one notable exception - the leaves of common buckthorn are still green and clinging to the branches and twigs of the plants. The green leaves make it easy to see just how invasive this woody plant is as it is displacing the desirable native plants at an alarming rate.
Buckthorn, a small, shrubby tree, is a non-native species. In 1999, Buckthorn was identified as a restricted noxious weed. This means that its sale, transportation or movement is prohibited statewide by the Minnesota Department of Agriculture.
If Buckthorn is non-native, how did it get here in the first place? Until the 1930s, it was sold as a popular hedge by our nursery industry. Many older homes still have buckthorn hedges. These prolific, fruit bearing shrubs attract birds that spread the seeds through their droppings. This has allowed large quantities of buckthorn to spread over a wide and diverse area of the state. Buckthorn out-competes our native plants for nutrients, light and moisture; degrades and threatens the future of wildlife habitat; contributes to erosion of the forest floor; serves as a host to other pests such as soybean aphid; forms an impenetrable layer of vegetation in our natural areas; and lacks natural controls that would curb its growth.
Autumn is a good time to remove buckthorn because it is easy to spot. In the late fall, when native shrubs and trees have lost their leaves, buckthorn will often still have green leaves into December. Common buckthorn has dark green leaves with curved main veins that remain green in the fall after other species have lost their foliage. The twigs are tipped with a short, sharp thorn and the female plants produce blue-black berries that have numerous seeds. The berries are toxic to humans but are readily eaten by birds and, having a laxative effect, the seeds are readily spread from place to place. The seeds remain viable in the soil for about six years.
Do you have buckthorn on your property? If so, here are some suggestions for getting rid of this dreaded invader.
Cut down all buckthorn trees greater than three inches in diameter. Buckthorns of this size produce berries.
Dig out the stumps or treat them with a herbicide. Of the several chemicals that work well, the two most common ones are glyphosate (Roundup) and triclopyr (Brush-B-Gon). Be sure to use chemicals properly, following all label instructions.
Pull up small trees (less than one inch) by hand. They do not have strong roots.
Remove seedlings with a hoe.
Replace buckthorn with native species. Some good substitutes for buckthorn are high bush cranberry, nannyberry, chokecherry, grey dogwood, pagoda dogwood, American hazelnut and black chokeberry.
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Until next time, happy gardening!
"For man, autumn is a time of harvest, of gathering together. For nature, it is a time of sowing, of scattering abroad."
- Edwin Way Teale