Buckthorn is most easily identified by its glossy egg-shaped leaves, which are pointed at the tip and contain 3-5 well-defined veins. The bark is brown with elongate silvery corky projections, and when cut reveals orange heartwood and yellow sapwood. Buckthorn commonly grows 20-25 feet in height, but at several locations in Cowling Arboretum entire stands are well over this height.

Caution: the bark of buckthorn is similar to that of native cherry trees. Among other small differences, the branches of buckthorn tend to grow far more cockeyed and angled that that of cherry trees.

Negative effects of Buckthorn on ecosystems:

  • Out-competes native plants for nutrients, light, and moisture
  • Degrades wildlife habitat
  • Wide tolerance level and aggressive growth shades out the woodland understory and prairies.
  • By shading out ground cover buckthorn contributes to erosion and a decrease in soil moisture.
  • Serves as host to other pests, such as crown rust fungus and soybean aphids.
  • Forms an impenetrable layer of vegetation.

Other Info:

Of Eurasian origin, buckthorn was introduced to the Upper Midwest in the mid 1800’s as a hedge plant. Those who planted it in the region soon found it to be uncontrollable. Buckthorn is currently one of the most problematic invasive species in Minnesota and the surrounding states, and clearing buckthorn to make way for the restoration of our native habitats has been one of the major goals of the Carleton Arboretum. Current removal projects include the forests of the Upper Arboretum, the north and west shores of Kettlehole Marsh, and in the oak savanna restorations in the Lower Arboretum.

Cowling Arboretum Procedures for Removal:

Medium size buckthorn plants may be removed with hand tools but the larger specimens (the Arb record trunk is a foot in diameter) must be cut with a chain saw or other heavy equipment. Cut stems must be carefully treated with herbicide or they will re-sprout. Once all the standing buckthorn is removed from an area the increase in sunlight will lead to the sprouting of new seedlings and smaller buckthorn plants will grow large enough to find and remove. These smaller plants are pulled if they are not too dense, or a second application of herbicide might be required. In habitats that are managed with fire, like prairies, oak savanna or oak dominated forests, regular management fires can keep the buckthorn to low numbers. Wetter habitats like floodplain forests will require constant vigilance to keep buckthorn from retaking the site.