Sweet Flag, also known as calamus and various other names, (Acorus calamus) is a plant from the Acoraceae family, in the genus Acorus. It is a tall perennial wetland monocot with scented leaves and more strongly scented rhizomes, which have been used medicinally, for its odor, and as a psychotropic drug. Its Sanskrit name is vacha. Probably indigenous to India, Acorus calamus is now found across Europe, in southern Russia, northern Turkey, southern Siberia, China, Japan, Burma, Sri Lanka, Australia, as well as southern Canada and the northern USA, where it may be mistaken for the native Acorus americanus.