Berberis

1. Leaves compound, evergreen; stem without spines (but leaflets spiny-toothed); ripe fruits dark blue.

2. Leaves smooth beneath.

B. aquifolium

2. Leaves papillose beneath (most easily seen along larger veins where papillae can be viewed from the side).

B. repens

1. Leaves simple, deciduous; stem spiny at nodes; ripe fruits red.

3. Leaves entire (at most with an apiculus or small terminal spine); flowers solitary or in small clusters.

B. thunbergii

3. Leaves with spiny-toothed margins; flowers in a raceme.

B. vulgaris

All species found in Berberis

Berberis aquifoliumOREGON-GRAPE 
Berberis repensCREEPING OREGON-GRAPE 
Berberis thunbergiiJAPANESE BARBERRY 
Berberis vulgarisCOMMON BARBERRY 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. March 30, 2017. http://michiganflora.net/genus.aspx?id=Berberis.