The Buckthorns (Rhamnus) are a genus (or two genera, if Frangula is treated as distinct) of about 100 species of shrubs or small trees from 110 m tall (rarely to 15 m), in the buckthorn family Rhamnaceae. They are native throughout the temperate and subtropical Northern Hemisphere, and also more locally in the subtropical Southern Hemisphere in parts of Africa and South America. Both deciduous and evergreen species occur. The leaves are simple, 315 cm long, and arranged either alternately or in opposite pairs. One distinctive character of many buckthorns is the way the veination curves upward towards the tip of the leaf. The plant bears fruits which are dark blue berries. The name is due to the woody spine on the end of each twig in many species. The genus is divided into two subgenera, sometimes treated as separate genera: Some species are invasive outside their natural ranges.
Contributions by Hardyplants, Bumper12, and MPF.