This is a widespread eastern species, with variation that needs further study. Most material in Ky. is probably referable to the typical variety. Also, var. grimesii Fern. & Weatherby is recorded from LETC (B); var. camporum (Rydb.) Fern. & Weatherby is recorded from CALL (MUR); and forma glandulosum Fern. is recorded from FULT (KY). Lower leaves of canadense have distinctive mottled appearance, mostly deep bluish green but with whitish upper vein surfaces. Also, they vary much in shape from simple to pinnate, and usually some have relatively large basal pinnae, making an overall deltoid outline to the leaf. These features appear to be less pronounced or absent in other species of the genus, but more systematic description is needed.