Based on recent treatements (reviewed in FNA 22 and W), almost all plants of this genus in southeastern states are sterile triploid hybrids to be included in A. calamus, which is said to have been introduced from Europe for medicine and confection. The native A. americanus Raf. (= A. calamus var. americanus H.D. Wulff) includes only fertile diploids, and has mostly narrower leaves that lack a prominent mid-vein. Var. americanus occurs across northeastern states and adjacent Canada, but remains unknown in Mo., Ky. and most southern Appalachian regions. Vegetative plants are sometimes confused with those of the Iris virginica group; leaves of Acorus are generally narrower (mostly 0.5-2 cm versus 2.5-3 cm), more glossy (bright green versus gray- to bright green), and usually with a longer sheathing base (ca. 10-30% of length versus 0-10%). Rhizomes of Acorus have had much psychoactive, medicinal, culinary use, involving diverse sesquiternes; however, the phenylpropanoid, beta-asarone is a potential emetic or toxin in some plants (Raja et al. 2009, Dong et al. 2010). .