Scientific name

Acorus L.

Common names




Similar genera

Carex, Cyperus and other sedges, Iris, Juncus, Lachnanthes, Ophiopogon, Sparganium, Typha, Xyris, Zephyranthes

Native distribution

widespread in tropical and subtropical regions of the world

Species cultivated

Acorus calamus L. (and varieties)

A. gramineus Sol.

Adventive distribution

introduced into many parts of the world

Weed status

not weedy


reed-like, emergent

Brief description

Perennial. Erect plant with creeping rhizome. Leaves in two sheathed rows, opposite distichous, equitant, linear, aromatic, with prominent midrib. Inflorescence a spadix, yellow-green, borne on stem that is fused with a leaf, arising approximately midway along leaf length. Spadix elongate, with numerous tiny bisexual flowers, spathe absent.

Natural habitat

marshes, swamps, and open ponds

Additional comments

Acorus is often regarded as a close relative of the Arum family (Araceae) and is sometimes included in that family. This plant has been found to have various medicinal, insecticidal, and pharmacological qualities. Acorus spp. are used primarily as pond plants.

The taxonomy of the genus is complicated and currently accepted as two species, of which A. calamus has three varieties:
1. Acorus calamus L. – "Common sweet flag"; sterile triploid (native to Europe and Southern Asia).
-Acorus calamus var. americanus Raf.
-Acorus calamus var. angustatus Besser
-Acorus calamus var. calamus

2. Acorus gramineus Sol. ex Aiton – “Japanese sweet flag”; fertile diploid (China and Southeast Asia).