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Rhamnus cathartica
Rhamnus cathartica, the European buckthorn, common buckthorn, purging buckthorn, or just buckthorn, is a species of small tree in the flowering plant family Rhamnaceae. It is native to Europe, northwest Africa and western Asia, from the central British Isles south to Morocco, and east to Kyrgyzstan. It was introduced to North America as an ornamental shrub in the early 19th century or perhaps before, and is now naturalized in the northern half of the continent, and is classified as an invasive plant in several US states and in Ontario and Québec, Canada.
Rhamnus cathartica is a deciduous, dioecious shrub or small tree growing up to 10 metres (33 ft) tall, with grey-brown bark and often thorny branches. The leaves are elliptic to oval, 25–90 mm (1–3+1⁄2 in) long and 12–35 mm (1⁄2–1+3⁄8 in) broad; they are green, turning yellow in autumn, have toothed margins, and are arranged somewhat variably in opposite to subopposite pairs or alternately. The flowers are yellowish-green with four petals; they are dioecious and insect pollinated and bloom in April–June. The fruit is a globose black drupe, 6–10 mm (1⁄4–3⁄8 in) across, and contains two to four seeds.
In addition to the kindred Frangula alnus, Rhamnus cathartica may be visually confused with a plant of another family, Cornus sanguinea.
The species was originally named by Carl Linnaeus as Rhamnus catharticus, but this spelling was corrected to cathartica as the genus name Rhamnus is treated as being of feminine gender.
The seeds and leaves are mildly poisonous for humans and most other animals, but are readily eaten by birds, who disperse the seeds in their droppings. The toxins cause stomach cramps and laxative effects that may function in seed dispersal. The chemical compounds responsible for this laxative effect are anthraquinone and emodin. The species name cathartica and the common name purging buckthorn refer to this effect.
In 1994, R. cathartica was implicated in the outbreak of an idiopathic neurological disease in horses,[clarification needed] although no causative agent was officially identified. In trials where rodents were fed the leaves and stems of R. cathartica, glycogen metabolism became abnormal and glycogen deposits formed in the cytoplasm of liver cells. Abnormalities in glycogen metabolism lead to diabetes in humans.
Rhamnus cathartica is shade-tolerant, moderately fast-growing and short-lived. It is a food plant of the brimstone butterfly, Gonepteryx rhamni. The sulphur-yellow males are indicative of the presence of this species or of its alternative host, Frangula alnus.[citation needed]
Rhamnus cathartica is the alternate host for the rust disease of cereals caused by Puccinia coronata. Crown rust fungus results in leaf damage and reductions in photosynthesis during its transit in this species. Rhamnus cathartica is also the primary overwintering host in North America for a significant agricultural pest of soybeans, the soybean aphid.
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Rhamnus cathartica
Rhamnus cathartica, the European buckthorn, common buckthorn, purging buckthorn, or just buckthorn, is a species of small tree in the flowering plant family Rhamnaceae. It is native to Europe, northwest Africa and western Asia, from the central British Isles south to Morocco, and east to Kyrgyzstan. It was introduced to North America as an ornamental shrub in the early 19th century or perhaps before, and is now naturalized in the northern half of the continent, and is classified as an invasive plant in several US states and in Ontario and Québec, Canada.
Rhamnus cathartica is a deciduous, dioecious shrub or small tree growing up to 10 metres (33 ft) tall, with grey-brown bark and often thorny branches. The leaves are elliptic to oval, 25–90 mm (1–3+1⁄2 in) long and 12–35 mm (1⁄2–1+3⁄8 in) broad; they are green, turning yellow in autumn, have toothed margins, and are arranged somewhat variably in opposite to subopposite pairs or alternately. The flowers are yellowish-green with four petals; they are dioecious and insect pollinated and bloom in April–June. The fruit is a globose black drupe, 6–10 mm (1⁄4–3⁄8 in) across, and contains two to four seeds.
In addition to the kindred Frangula alnus, Rhamnus cathartica may be visually confused with a plant of another family, Cornus sanguinea.
The species was originally named by Carl Linnaeus as Rhamnus catharticus, but this spelling was corrected to cathartica as the genus name Rhamnus is treated as being of feminine gender.
The seeds and leaves are mildly poisonous for humans and most other animals, but are readily eaten by birds, who disperse the seeds in their droppings. The toxins cause stomach cramps and laxative effects that may function in seed dispersal. The chemical compounds responsible for this laxative effect are anthraquinone and emodin. The species name cathartica and the common name purging buckthorn refer to this effect.
In 1994, R. cathartica was implicated in the outbreak of an idiopathic neurological disease in horses,[clarification needed] although no causative agent was officially identified. In trials where rodents were fed the leaves and stems of R. cathartica, glycogen metabolism became abnormal and glycogen deposits formed in the cytoplasm of liver cells. Abnormalities in glycogen metabolism lead to diabetes in humans.
Rhamnus cathartica is shade-tolerant, moderately fast-growing and short-lived. It is a food plant of the brimstone butterfly, Gonepteryx rhamni. The sulphur-yellow males are indicative of the presence of this species or of its alternative host, Frangula alnus.[citation needed]
Rhamnus cathartica is the alternate host for the rust disease of cereals caused by Puccinia coronata. Crown rust fungus results in leaf damage and reductions in photosynthesis during its transit in this species. Rhamnus cathartica is also the primary overwintering host in North America for a significant agricultural pest of soybeans, the soybean aphid.