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Invasive Species |
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Tree Killers
Common Buckthorn or European Buckthorn
(Rhamnus cathartica)
 Photo 6: Stephen L. Solheim, University of Wisconsin, Stevens Point Biology
- large shrub or small tree (up to 6 m or 20 ft tall) with thorny twigs and strongly-veined leaves that remain on the plant late in the fall
- male and female flowers on separate individuals
- female tree produces large numbers of dark berry-like fruits, singly or in small groups, along younger branches at the base of the oval-shaped leaves
- leaves have serrated edges unlike Glossy Buckthorn whose leaves have smooth edges
- leaves come out early in spring and remain on the plant until late fall which shades out most native plants
- fruits, leaves, and bark are cathartic (purging) to most animals but birds eat them readily
- birds are largely responsible for the spread of Common Buckthorn since the seeds within the fruit pass through the bird without damage
- seeds remain viable for up to three years and have a high germination rate
- tolerates a wide range of upland habitats including forests and woodland edges
History in Canada
- brought to North America in the late 1800's for landscape planting
- most abundant in southern Ontario but also occurs west to Saskatchewan and east to Prince Edward Island
- still available from nurseries
 Photo 23: Leslie J. Mehrhoff, University of Connecticut Impact on Trees
- grows in dense stands that suppress native tree seedlings due to heavy shade
- may produce a substance that inhibits the growth of other species
Control
- cutting or girdling stems followed by herbicide application to the cut stems or later removal of sprouts that develop after cutting or girdling
- grows later in the season than most native plants so fall application of herbicide can be effective with little impact on nearby native species
- annual or biennial burns
- mowing younger stands
- several years of control are needed since seeds are unaffected by the above methods and seedlings can quickly recolonize an area
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