Recognition of Frangula follows Bolmgren & Oxelman (2004).
1. Pedicels of flowers (and fruiting peduncles) glabrous or nearly so; leaf blades 2.5–8 cm long.
1. Pedicels of flowers and fruiting peduncles pubescent; leaf blades ca. 8–12 cm long.
All species found in Frangula
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 15, 2017. http://www.michiganflora.net/genus.aspx?id=Frangula.