This diploid (2n = 20) is widespread on wet medium-acid soils across eastern states, except those adjacent to Canada. See also perfoliatum for note on hybrids. With a history of diverse medicinal uses, this species and probably others in the genus contain potent pyrrolizidine alkaloids (Roemer et al. 2015), sesquiterpene-lactones (Seaman 1982) and other compounds (Herz 2001).