200609 common St. Johnswort (Hypericum perforatum) - USDA Illustration
%20-%20USDA%20Illustration.jpg "200609 common St. Johnswort (Hypericum perforatum) - USDA Illustration.jpg")
Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 2
USDA, NRCS. 2023. The PLANTS Database (http://plants.usda.gov). National Plant Data Team, Greensboro, NC 27401-4901 USA.