Buckthorns (Rhamnus) are a genus (or two genera, if Frangula is treated as
distinct) of about 100 species of shrubs or small trees from 1-10 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, 3-15 cm long, and arranged either alternately or in opposite pairs. One semi-unique characteristic 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 comes from the fact that there is a woody spine on the end of each twig in many species