This widespread eastern biennial (or short-lived perennial) is curiously local in Ky. It occurs mostly on moderately fertile, base-rich soils, in thin subxeric woods with a history of disturbance from browsing or burning. Hybridization with discolor appears to occur locally in midwestern regions (FNA 19, Y); it has not been clearly documented in Ky. but some plants are suggestive. C. altissimum usually has lower chromosome number (2n = 18 versus 20), leading to sterility in hybrids.