Acorus americanus

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American sweet flag
Acorus americanus USFS-1.jpg
Scientific classification e
Kingdom: Plantae
Clade: Angiosperms
Clade: Monocots
Order: Acorales
Family: Acoraceae
Genus: Acorus
Species: A. americanus
Binomial name
Acorus americanus

Acorus americanus, the American sweet flag, is an emergent wetland plant native to the northern United States and Canada. This perennial plant has bright green blade-shaped leaves that arise directly from the rhizomes and sheath into each other at the base. Additionally the blades have 2-6 raised veins, and a swollen center when viewed in cross section. The foliage has a citrus-like spicy aromatic quality, and can be used to flavor beer. It is a flowering plant with inconspicuous flowers that are arranged on a lateral spadix (a thickened, fleshy axis) and the fertilized flowers produce berries with a jelly inside. This plant is protected as a state endangered species in Pennsylvania.[1]


The name "Acorus" is derived from the Greek word 'acoron', a name used by Dioscorides, which in turn was derived from 'coreon', meaning 'pupil', because it was used in herbal medicine as a treatment for inflammation of the eye.

The species name, "americanus" simply indicates that this is an American species of this genus, differentiating it from the very similar European and western Asian species Acorus calamus.


Acorus americanus was formerly classified as Acorus calamus var. americanus. It differs only in being a fertile diploid (2n = 24)], whereas most of the A. calamus of Europe and Asia is a sterile triploid species, that only spreads asexually. Diploid plants in northern Asia may be representatives of A. americanus.[2] Also as a diploid it does not produce b-asarone.


This plant was used extensively by Native Americans and early European settlers.


In 1968 the Food and Drug Administration banned Acorus calamus from being used as a food additive and as a medicinal as a result of lab studies that involved supplementing the diets of lab animals over a prolonged period of time with massive doses of isolated chemicals (β-asarone) from the Indian Jammu strain of Acorus calamus. The plant was labeled procarcinogenic.[3][4][5] Wichtl says “It is not clear whether the observed carcinogenic effects in rats are relevant to the human organism.”[6] However, most sources advise caution in ingesting strains other than the diploid strain.

Like the diploid strains of Acorus calamus in parts of the Himalayas, Mongolia, and C Siberia, the Acorus americanus diploid strain does not contain the procarcinogenic β-asarone.[7][8][9] Research has consistently demonstrated that “β-asarone was not detectable in the North American spontaneous diploid Acorus [Calamus var. Americanus]”.[10]

It is believed by some that calamus is a hallucinogen. This urban legend is based solely on two pages of a book written by Hoffer and Osmund entitled The Hallucinogens. The information on these two pages came from anecdotal reports from two individuals (a husband and wife) who reported that they had ingested calamus on a few occasions.[5][11] None of the components in calamus are converted to TMA (trimethoxyamphetamine) in the human organism.[11] To date there is no solid evidence of any hallucinogenic substances in Acorus calamus.

Calamus shows neuroprotective effect against stroke and chemically induced neurodegeneration in rats. Specifically, it has a protective effect against acrylamide induced neurotoxicity.[12]


  1. ^ NRCS: USDA Plants Profile: Acorus americanus
  2. ^ Flora of North America Editorial Committee (eds.). "Acorus americanus". Flora of North America North of Mexico (FNA). New York and Oxford – via, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA. 
  3. ^ "Code of Federal regulations, title 21". 
  4. ^ Natural carcinogenic products, EK Weisburger - Environmental Science & Technology, 1979 – ACS Publications
  5. ^ a b Herbcraft - Acorus calamus
  6. ^ Wichtl, Max, Herbal drugs and phytopharmaceuticals: a handbook, 2004
  7. ^ Chemical composition of the essential oil and supercritical CO2 extract of Commiphora myrrha (Nees) Engl. and of Acorus calamus L.B Marongiu, A Piras, S Porcedda… - J. Agric., 2005 - ACS Publications
  8. ^ (Rost and Bos, 1979)
  9. ^ Antimicrobial activities of the crude methanol extract of Acorus calamus Linn., S Phongpaichit, N Pujenjob, J. Songklanakarin
  10. ^ Essential oil composition and antimicrobial assay of Acorus calamus leaves from different wild populations, J Radušienė, A Judžentienė… - Plant Genetics, 2007 - Cambridge Univ Press, 1982; Lander and Schreier, 1990
  11. ^ a b Calamus (Acorus calamus)
  12. ^ Shukla PK, Khanna VK, Ali MM, Maurya R, Khan MY, Srimal RC. "Neuroprotective effect of Acorus calamus against middle cerebral artery occlusion-induced ischaemia in rat" Hum Exp Toxicology (April 2006) 25(4):187-94. PMID 16696294; Shukla PK, Khanna VK, Ali MM, Maurya RR, Handa SS, Srimal RC. "Protective effect of acorus calamus against acrylamide induced neurotoxicity" Phytother Res. (May 2002) 16(3):256-60. PMID 12164272

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