Common Buckthorn

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Common Buckthorn

(Rhamus cathartica)

Identification: It is a small tree or large shrub, which grows up to about 7 m (20 feet). It usually has multiple trunks, which become covered in shaggy bark as it matures. Twigs often end in short sharp spikes.

Buckthorn bark  Buckthorn twig

(All photos by John Oyston. Oak Hills Farm and Toronto)

 Inner bark is yellow and the heartwood is orange. It has dark green oval leaves.

Buckthorn leaves

The berries tend to be left on the bushes until late winter, and are only eaten when food has become scarce. It has a laxative effect on birds, which helps distribute the seed widely.

 

Buckthorn berries

 

Introduction:

Buckthorn was introduced into North America from Europe in the early 19th century as an ornamental plant, and it was widely planted as a hedge.

Problem:

Common buckthorn invades forests, prairies and savannas in the Midwestern United States and can form dense thickets crowding out native shrubs and understory plants. It is also a problem in farmlands in Ontario.

It is shade tolerant and drought resistant. It rapidly produces stands which prevent other species growing, and it is a overwintering host for the soybean aphid. Buckthorn has become so widespread that it has taken over many hedgerows.

Control:

Elimination will only be achievable on small properties. In larger areas, it is a matter of controlling Buckthorn by eliminating the larger seed-bearing shrubs. Seeds remain viable in the soil for up to five years, so even after apparent elimination of mature Buckthorns, repeated efforts need to be made to remove new seedlings.

Physical methods of elimination include burning, flooding, grazing, and mowing.  Pulling up seedlings may result in vigorous re-sprouting. Girdling is only effective if followed immediately by applying herbicide. Foliar herbicides, applied from leaf out until mid-July. may be effective, but the agent proven to be most effective is triclopyr, which is banned in many jurisdictions.

Cutting down mature specimens with a chain saw must be followed by the application of herbicide such as glyphosate within 24 hours to prevent resprouting.

Buckthorn stumpsPile of cut Buckthorn

Availability and Alternatives:

Common Buckthorn does not seem to be sold in North America. Alternatives recommended by the Invasive Plant Atlas are:

Cornus racemosa (gray dogwood)
Euonymus atropurpureus (burningbush)
Frangula caroliniana (Carolina buckthorn)
Hamamelis virginiana (American witchhazel)
Photinia melanocarpa (black chokeberry)
Ptelea trifoliata (common hoptree)
Staphylea trifolia (American bladdernut)
Viburnum prunifolium (blackhaw)