200511 common Buckthorn (Rhamnus
cathartica) - USDA Illustration
%20-%20USDA%20Illustration.jpg "200511 common Buckthorn (Rhamnus cathartica) - USDA Illustration.jpg")
USDA-NRCS PLANTS Database / Britton,
N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada.
Vol. 2
USDA, NRCS. 2012. The PLANTS Database (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.