October’s Weed of the Month is a widespread, woody, understory shrub or tree called common buckthorn (Rhamnus cathartica). Native to Europe and Asia, it was introduced to North America as an ornamental shrub and used for living fence rows and wildlife habitat. Having escaped cultivation, common buckthorn has spread aggressively across most of the upper Midwest.
Common buckthorn thrives in a variety of landscapes, crowds out and displaces native understories, and prevents natural regeneration of forest species. It is also a threat to agricultural producers because it can serve as an alternate host for alfalfa mosaic virus, oat crown rust, and soybean aphid.
Common buckthorn has many distinctive characteristics to distinguish it from native understory shrubs and trees. Plants are either male or female, and only female plants produce fruit. The plants produce small round berries in clusters, and the berries are shiny black. Birds consume the fruit and spread the seed.
Common buckthorn plants can reach a height of 20 feet and can be single or multi-stemmed. The leaves are oval, smooth, glossy, and have distinctive veins that radiate outward from a central mid-vein. The leaves stay green late into the fall after most other trees and shrubs have dropped their leaves, making fall a good time of year to identify the plant. It also has small sharp thorns at the ends of the branches.
Common buckthorn and all cultivars are restricted from being transported, sold, or intentionally propagated in Minnesota. It is recommended that this species be prevented from spreading to new areas and that smaller populations be eradicated.
Because common buckthorn produces abundant fruit that is attractive to birds and is an aggressive competitor, prevention and management can be challenging:
For additional management strategies, please visit the Minnesota Department Agriculture’s website on common buckthorn management.