This southern Appalachian species is close to gronovii. Both species have a thickened ridge at base of style, but gronovii also has a distinctly beaked ovary apex, and rostrata has larger flowers, fruits and seeds; for details see W, Spaulding (2013b) and their citations. C. rostrata has been reported from BELL, with a coll. by R. Cranfill (Univ. of California, Berkley) that needs to be checked (M). In Tenn. (Ch) and Ala. rostrata is known only from the Blue Ridge, mostly on Asteraceae.