Sp. Pl. 1: 324. 1753
Illustrator: John Myers
Phenology: Flowering early spring–early summer.
Habitat: Wet open areas, marshes, swales, and along edges of quiet water
Elevation: 0–900 m
N.B., N.S., Ont., Que., Ala., Ark., Calif., Colo., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis., Europe, Asia, Africa, Indian Ocean Islands, Pacific Islands.
Acorus calamus, a sterile triploid, was introduced to North America by early European settlers, who grew it for medicinal uses. Rhizomes propagate easily, and the species has spread throughout northeast and central United States. Scattered populations occur elsewhere. Although leaf and spadix size of A. calamus and A. americanus overlap, those measurements differ significantly, with A. calamus in general having longer and wider leaves and longer spadices.