Acorus calamus is a non-flowering aquatic perennial rush or sedge in the acorus family, native to Central Asia and widely naturalized across temperate regions of the world. The sword-shaped leaves emerge erect and bright green from a spreading rootstock, aromatic when crushed with a complex scent combining cinnamon, ginger, and something iris-like that is immediately distinctive. The inconspicuous green flowering spadix appears in spring among the leaves. Growing 2 to 2.5 feet in zones 4 to 10, it spreads by rhizome to form a dense colony in the right conditions.

It requires consistently moist to wet soil or shallow standing water and controls erosion effectively along stream banks and pond margins. For water gardens, boggy areas, and rain gardens across a wide climate range, Sweet Flag provides reliable structure, year-round presence, and a fragrance that sets it apart from any other aquatic plant. The root has a long history in traditional medicine and as a flavouring in the production of certain bitters and liqueurs.