Rhamnus

Rhamnus is a genus of flowering plants in the buckthorn family, Rhamnaceae. It comprises about 90–100 species of deciduous shrubs and small trees native to Europe, Asia, and Africa; several species have been introduced elsewhere for ornamental use and hedges and have become naturalized or invasive, notably the common buckthorn (Rhamnus cathartica) in North America.

Morphology and ecology: Members typically have simple, alternate leaves with finely toothed margins. Small, greenish flowers appear in clusters; many species are dioecious, with separate male and female plants. The fruits are small drupes that ripen to black and are dispersed by birds, often forming dense thickets that shade competing vegetation. Birds that feed on the fruit help spread the seeds widely.

Taxonomy: The classification of buckthorns is subject to revision. Some species formerly placed in Rhamnus have been moved to Frangula; for example, Rhamnus frangula is now Frangula alnus. The genus remains a core group within Rhamnaceae, including ornamentals such as R. cathartica and related species.

Uses and impact: Historically, parts of some species have been used for their laxative properties due to anthraquinone glycosides; the name cathartica reflects this use. In horticulture, buckthorns are valued for hardiness and dense growth, but in non-native regions, they can form invasive thickets that displace native flora.