Rhamnus cathartica

Rhamnus cathartica, commonly known as the European buckthorn, common buckthorn, or purging buckthorn, is a species of small tree in the flowering plant family Rhamnaceae. This deciduous, dioecious shrub or small tree is indigenous to Europe and western Asia, and has been introduced to North America as an ornamental shrub.

Botanical Description

Rhamnus cathartica can grow up to 10 meters (33 feet) tall, featuring grey-brown bark and often thorny branches. The leaves are arranged oppositely and are simple, broadly elliptic, and dark green. The plant is known for its small, greenish-yellow flowers that bloom in spring. The fruit is a small black drupe, which is mildly toxic when unripe, containing compounds such as emodin which may deter herbivores and protect against pathogens.

Ecological Impact

Rhamnus cathartica is considered an invasive species in several regions, including parts of the United States and Canada. It was brought to North America in the early 19th century and has naturalized in the northern parts of the continent. As an invasive plant, it poses threats to native flora and fauna by altering the nutrient cycles in temperate deciduous forests and competing for resources.

The plant is also the primary overwintering host for the soybean aphid, a significant agricultural pest affecting soybean crops in North America.

Chemical Properties

Rhamnus cathartica is a constitutive isoprene emitter, influencing atmospheric chemistry. Its secondary compounds, particularly emodin, are found in the fruit, leaves, and bark. These compounds may reduce germination rates of other plant species due to allelopathic effects from leaf litter and exudates.

Uses

Despite its invasiveness, Rhamnus cathartica has been used in traditional medicine for its purgative properties. However, caution is advised due to its toxicity.

Relations to Other Species

Rhamnus cathartica is closely related to other species in the Rhamnus genus, such as Frangula alnus, also known as alder buckthorn. Both serve as food plants for the common brimstone butterfly (Gonepteryx rhamni).