Acorus calamus L.
  • Sp. Pl.

This taxon is accepted by Acoraceae
Notes: More details could be found in The Plant List v.1.1. Originally in The Plant List v.1.0

General Description

Rhizome stout, 4-10(-20) × (0.8-)1-1.5(-3) cm, aromatic; roots at lower side of rhizome. Leaves several, mid-green, often reddish at base, ensiform, (60-)70-100(-150) × (0.7-)1-2(-2.5) cm (mostly 1-1.5 cm wide), apex acuminate; midrib conspicuous on both sides. Peduncle compressed triangular, (15-)40-50 cm. Spathe mid-green, leaflike, 30-50 cm, acute. Spadix straight or slightly curved, erect, oblique, narrowly conic to subcylindric (tapering toward apex), 4.5-6.5(-8) × 0.6-1.2(-1.5) cm, densely flowered. Flowers yellowish green, 1.8-2 mm in diam. seen from above; tepals oblong, 2.5-3 × 1-1.2(-1.4) mm, keeled, membranous, apex triangular hooded; filaments oblong, flat, 2-2.5 × 0.3-0.5 mm, anthers cream-colored, 0.4-0.5 mm in diam.; pollen grains ca. 20 µm, exine shallowly and remotely foveolate; gynoecium obconic-cylindric, 2.5-3.5(-4) × (0.8-)1-2.3 mm, with conic, spongy apex and stigma very small. Infructescence 1.5-2 cm in diam., straw-brown at maturity, berries densely arranged. Berry oblong-obovoid, 1- to few seeded, (3.5-)4-4.5 × 2-3(-3.5) mm. Seed oblong-ellipsoid to ovoid, 2.5-3(-4) × 1-1.2(-1.8) mm, without bristles; testa light brown, subsmooth and slightly foveolate. Fl. (Feb-)Apr-Sep. 2n = 24, 36, 48.

For a full synonymy, see Govaerts et al. (World Checkl. & Bibliogr. Araceae, 545-553. 2002).

Acorus calamus is diploid, triploid, and tetraploid. Diploids are known to grow naturally in E Asia (Mongolia and C Siberia, at least) and North America; tetraploids are known only from Asia (India, E Siberia, and Japan); and triploids are typical for the plants in Europe, SW Asia, India (Himalayan region), and E North America. The triploid cytotype probably originated in the Himalayan region, as a hybrid between the diploid and tetraploid cytotypes. It then probably dispersed naturally or with humans to Sakhalin and with humans to Turkey, then to Europe, and finally to E North America as a medicinal plant (Evstatieva et al., Fitologiya 48: 19-22. 1996; Löve & Löve, Proc. Genet. Soc. Canada 2: 14-17. 1957).

The different cytotypes show a great morphological variability and also a large variation in the chemical composition of the essential oils from the rhizome and leaves. As a result, they have been considered as representing species or varieties: Acorus calamus var. calamus (or A. calamus var. vulgaris) for the triploids, A. calamus var. americanus for the diploids, and A. calamus var. angustus for the tetraploids. Acorus calamus is considered in this treatment as a variable species, and infraspecific taxa are not recognized because there is an overlap in the width of the leaves, from 0.8 cm to 1.5 or 2 cm, also from Asiatic collections from different geographical regions, and furthermore the length of the spadices is variable. It can be observed that several collections from Asia have somewhat narrower leaves, ca. 1 cm wide; but there are also broader ones, and there is a continuous series.

"Sweetly aromatic; lvs crowded at the base, erect, to 2 m, 8–25 mm wide; scape resembling the lvs, prolonged into an erect green spathe 2–6 dm; spadix 5–10 cm, 1 cm thick at anthesis, 2 cm at maturity, covered with yellowish-brown fls; fr 4–5 × 2 mm; 2n=18, 24, 36, 48. Swamps and shallow water; irregularly circumboreal, in Amer. from N.S. and Que. to Minn., Alta., and e. Wash., s. to Fla., Tex., and Colo. Spring and early summer. (A. americanus)"


  • 1 "Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp."
  • 2 Sp. Pl.

 Information From

World Flora Online Data. 2017.
  • A CC0 1.0 Universal (CC0 1.0).
Flora Of China @
'Flora of China @ eFloras (2008). Published on the Internet [accessed August 2016]' Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  • B All Rights Reserved
New York Botanical Garden
Descriptions of plants should be attributed to the full citation for each individual article, chapter or book that is the source for each record, which should include the authors of original publication.
  • C Content licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License
World Flora Online consortium
World Flora Online Data. 2017.
  • D CC0 1.0 Universal (CC0 1.0).
International Union for Conservation of Nature
IUCN 2016. IUCN Red List of Threatened Species. Version 2016-2
  • E See IUCN Terms and conditions of use