This tall herb is widely distributed in low meadows, old fields, roadside ditches and thickets on damp soils in eastern states, except for the upper mid-west and on lowlands along the Mississippi Rv. and Ohio Rv (K). In Ky. it is rare to absent on more fertile base-rich soils, where intense browsing by groundhogs, deer and other animals appears to be a locally important factor, in addition to any presumed direct edaphic effect. A few colls. have been difficult to distinguish from purpureum, but hybrids are not documented in Ky. E. fistulosum differs (W) in its internodes, which are largely hollow (versus almost solid), usually purplish throughout and strongly glaucous when fresh (versus usually with little purple except at nodes and with litle or no glaucous surface). Leaves are mostly in whorls of 4-6 (versus 3-4) and tend to be more elongated with L/W ca. 3.5-5.5 (versus 2.5-4). Plants are up to 3.5 m tall or more (versus 2 m in congeners). Flowers tend to be brighter pink.