"Alder Buckthorn. Buckthorn, the name of an extensive genus of trees and shrubs, order Rhamnaceae."…
Of the buckthorn family (Rhamnaceae), the common buckhorn or Rhamnus cathartica.
Of the buckthorn family (Rhamnaceae), New Jersey tea or Ceanothus americanus.
The flower of a Buckthorn.
The flower of a Buckhorn, cut in half.