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. It may be unpalatable to livestock and often does well in farm ponds. The native A. americanus Raf. (= A. calamus var. americanus H.D. Wulff) is a more northern species that includes only fertile diploids; it has mostly narrower leaves (3-13 mm versus 5- 20 mm) that lack a prominent eccentric mid-vein (as in calamus) and that lack an undulate or crisped margin (as often in calamus). A. americanus occurs across northeastern states and adjacent Canada, but remains unknown in Mo., Ky. and most southern Appalachian regions. Vegetative plants of calamus are sometimes confused with plants of the Iris virginica group, which tend to have a less prominent mid-vein (but still eccentric). Leaves of calamus are also generally narrower (mostly 5-20 mm versus 25-30 mm), 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 or 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). .