Classification
The genus is divided into two subgenera, sometimes treated as separate genera:
- Subgenus Rhamnus: flowers with four petals, buds with bud scales, leaves opposite or alternate, branches with spines. Species include:
- Rhamnus alaternus – Italian Buckthorn
- Rhamnus alnifolia – Alderleaf Buckthorn
- Rhamnus arguta – Sharp-tooth Buckthorn
- Rhamnus cathartica – Common (or Purging) Buckthorn (syn. R. catharticus)
- Rhamnus crocea – Redberry Buckthorn (ssp. crocea), Hollyleaf Buckthorn (ssp. pilosa)
- Rhamnus davurica – Dahurian Buckthorn
- Rhamnus diffusus
- Rhamnus globosa – Lokao Buckthorn
- Rhamnus ilicifolia – Hollyleaf Redberry
- Rhamnus japonica – Japanese Buckthorn
- Rhamnus lanceolata – Lanceleaf Buckthorn
- Rhamnus libanotica
- Rhamnus lycioides
- Rhamnus palaestinus - endemic to Israel
- Rhamnus petiolaris - endemic to Sri Lanka
- Rhamnus pirifolia – Island Redberry Buckthorn
- Rhamnus prinoides – Shiny-leaf Buckthorn
- Rhamnus saxatilis – Rock Buckthorn, Avignon Buckthorn, Avignon Berry (syn. R. infectoria, R. infectorius)
- Rhamnus serrata – Sawleaf Buckthorn
- Rhamnus smithii – Smith's Buckthorn
- Rhamnus staddo – Staddo (syn. R. rhodesicus)
- Rhamnus utilis – Chinese Buckthorn
- Subgenus Frangula: flowers with five petals, buds without bud scales, leaves always alternate, branches without spines. Species include:
- Rhamnus betulaefolia (Frangula betulifolia) – Birchleaf Buckthorn
- Rhamnus californica (Frangula californica) – California Buckthorn, Coffeeberry
- Rhamnus caroliniana (Frangula caroliniana) – Carolina Buckthorn, Indian Cherry (syn. R. carolinianus)
- Rhamnus frangula (Frangula alnus) – Alder Buckthorn, Glossy or Breaking Buckthorn, Black Dogwood
- Rhamnus glandulosa - Sanguinho
- Rhamnus purshiana (Frangula purshiana) – Cascara Buckthorn (syn. R. purshianus)
- Rhamnus rubra (Frangula rubra) – Red Buckthorn
Read more about this topic: Buckthorn