Common buckthorn, a small tree, is native to Europe and Asia and invasive to North America. The species produces black berries that have a cathartic or laxative effect. The Anglo-Saxons, who settled in England in the fifth and sixth centuries, reported the use of common buckthorn in their medical writings. In the thirteenth century, Welsh physicians prescribed the juice of the berries to relieve constipation. In the 18th and 19th centuries, American Dispensatory also stated that the ripe berries have a powerful cathartic effect and suggested it should be consumed in the form of syrup. Indeed, until the late 19th century, a syrup was created for children using common buckthorn juice mixed with pimento, ginger, and sugar. However, the medicinal use of common buckthorn for humans was eventually discontinued since the cathartic effects of the berries is simply too powerful, causing excess dehydration. Common buckthorn is however occasionally used as a purgative on dogs in veterinary medicine.
Common buckthorn was introduced to North America in the 19th century as an ornamental plant and has become naturalized across many regions of the continent due to its highly invasive properties. Common buckthorn produces its leaves very early in the spring and retains them until the late fall as one of the last trees to lose its leaves. This allows the species to shade out native species, preventing them from photosynthesizing. The prolonged lack of photosynthesis in plants is analogous to humans being deprived of food, and similarly, shaded plants typically die eventually. This can lead to reduced biodiversity underneath and around the shade-casting buckyhorn. Besides outcompeting native species for light, common buckthorn also produces an allelopathic chemical called emodin. Allelopathic chemicals are plant-produced chemicals that reduce germination, growth, or survival of neighboring plants. Along with outcompeting native species for light, the production of the allelochemical thus gives buckthorn a double edge over native species in its introduced range. This has resulted in common buckthorn being declared the worst invasive woody species in southern Ontario.
Original text by Anfal Patel, rewritten by Ivana Stehlik
Buckthorns. A Modern Herbal. Retrieved June 29, 2022, from https://www.botanical.com/botanical/mgmh/b/buckth80.html#com
Common Buckthorn. https://www.ontario.ca/page/common-buckthorn. Retrieved June 29, 2022.
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Photo credit: Robert Flogaus-Faust, CC BY 4.0 (https://creativecommons.org/licenses/by/4.0), via Wikimedia Commons