This is a variable alien (2n = 56 or 84) that has been widely grown for ornament, and it is locally persistent or escaped across northern states and adjacent Canada. On the southern side of its current range, the species is concentrated along or near the Ohio Rv. and the New Rv. (K). Ky. records are restricted to counties along the Ohio Rv., where it generally occurs in seasonally wet fields or ditches within a mile of the river. It has spread rapidly in Ky. since the first record was made during 1981 (by MM in JEFF). The species is probably much more frequent than mapped records indicate. It is possibe that dispersal has been largely vegetative, through movement of rhizome segments by floods.