This perennial is widespread in open wetlands of eastern North America, usually on medium acid soils. It is often confused with obstusum; see notes under that name. Old reports of G. trifidum L. from Ky. are referable to tinctorium (M); these species were combined in earlier treatments. Variation needs further study: var. floridanum Wieg. is a more robust southern segregate with larger fruits and leaves that has been reported from southern Ky. (Puff 1976; W). Puff elevated the two taxa to subspecies, but noted: "The separation... sometimes becomes problematic where their distribution overlaps because intergrading seems to take place." He mapped three colls. of floridanum in Ky., to the west and south, and three to the north and east.