Keep an Eye Out for Buckthorn!

In the fall and early winter, as temperatures get colder and our native trees lose their leaves in preparation for the cold winter ahead, you may notice some shrubs can retain their green leaves well into late fall and even early winter. Most likely, these shrubs are common or glossy buckthorn, an invasive shrub commonly found overtaking forest understories throughout the Midwest. Buckthorn outcompetes native forest plants by growing leaves early in the spring before most native plants have an opportunity to grow. Then, in the fall, buckthorn is able to grow later in the season than most other native trees and shrubs by retaining its leaves longer. These adaptations allow buckthorn populations to expand rapidly, which decreases the nutrients and habitat available for our native understory plants.

However, because buckthorn leaves stay green so much longer than other tree species, fall and early winter are ideal times to identify any buckthorn you may have on your property. Buckthorn shrubs can grow up to 20 inches tall, and there is often a small thorn at the node where two branches connect. Additionally, female trees will have large clusters of blue-black berries, which ripen in late summer and remain on the shrubs throughout the winter. 

Photo Credit: Maria Young

Fall is also an ideal time to chemically treat buckthorn. This is because, in the fall, a tree’s sap will flow towards its base to be stored in its roots for the winter. Therefore, any herbicides applied to a buckthorn plant in the fall will flow toward the roots of the plant, effectively killing it.  

For more information on herbicide application to treat buckthorn, see https://www.dnr.state.mn.us/invasives/terrestrialplants/woody/buckthorn/index.html or https://extension.umn.edu/yard-and-garden-news/fall-good-time-remove-buckthorn 

Additionally, if you own property located in St. Croix, Polk, Barron, Washburn, or Burnett county in Wisconsin, and you are interested in learning about how to treat buckthorn on your land, keep an eye out for information about the St. Croix-Red Cedar Cooperative Weed Management Area buckthorn removal landowner workshops happening fall 2025. If interested, please contact Maria Young, SC-RC CWMA coordinator, to be put on a notify list!

Email: myoung@wildriversconservancy.org   

Phone: 715-483-3300 ext. 21