Rhamnus utilis Decne.
Common Name: BUCKTHORN
Coefficient of Conservatism: *
Coefficient of Wetness: 5
Wetness Index: UPL
Physiognomy: Ad Tree

Rhamnus utilis A. A. Reznicek

An Asian species, locally established in old fields, thickets, and disturbed forests; first collected in 1980 in Washtenaw Co.

This species and Rhamnus davurica have leaves narrower than R. cathartica and more strongly cuneate-tapering to the base. The largest leaf blades of our specimens of R. utilis range up to 15 cm long; blades of our limited material of R. davurica are shorter, up to about 8 cm long, but still longer than R. cathartica. When growing together with R. cathartica, the fruit of R. utilis is still green when that of neighboring R. cathartica is fully ripe.

Rhamnus utilis is well established in some urbanized areas in Michigan, and hybrids with leaf shape intermediate between R. utilis and R. cathartica occur when the two grow together (Gil-ad & Reznicek, 1997). Some of these hybrid combinations might seem to resemble R. davurica, which seems to be distinctly less common in Michigan. Those hybrids with leaves as narrow as R. davurica, however, generally have their largest leaves up to 1012 cm long, and often with 5 pairs of veins. Caution is needed when identifying Rhamnus in mixed colonies. 

Locations

Kent County
Washtenaw County
Wayne County

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 11, 2017. http://www.michiganflora.net/species.aspx?id=2415.