Acorus calamus

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Sweet flag
Acorus calamus1.jpg
Sweet flag
Scientific classification edit
Kingdom: Plantae
Clade: Angiosperms
Clade: Monocots
Order: Acorales
Family: Acoraceae
Genus: Acorus
A. calamus
Binomial name
Acorus calamus
L., 1753

Acorus calamus (also called sweet flag or calamus, among many common names[2]) is a species of flowering plant, a tall wetland monocot of the family Acoraceae, in the genus Acorus.



Sweet flag is a herbaceous perennial, 30–100 cm (12–39 in) tall. In habit it resembles the iris, and has given its name to the flag iris, I. pseudacorus. It consists of tufts of basal leaves that rise from a spreading rhizome. The leaves are erect yellowish-green, radical, with pink sheathing at their bases, sword-shaped, flat and narrow, tapering into a long, acute point, and have parallel veins. The leaves have smooth edges, which can be wavy or crimped. The sweet flag can easily be distinguished from iris and other similar plants by the crimped edges of the leaves, the fragant odour it emits when crushed, and the presence of a spadix.

Only plants that grow in water bear flowers. The solid, triangular flower-stems rise from the axils of the outer leaves. A semi-erect spadix emerges from one side of the flower stem. The spadix is solid, cylindrical, tapers at each end, and is 5 to 10 cm in length. A covering spathe, as is usual with Acoraceae, is absent. The spadix is densely crowded with tiny greenish-yellow flowers. Each flower contains six petals and stamens enclosed in a perianth with six divisions, surrounding a three-celled, oblong ovary with a sessile stigma. The flowers are sweetly fragrant. In Europe, it flowers for about a month in late spring or early summer, but usually does not bear fruit. The fruit is a berry filled with mucus, which when ripe falls into the water and thus disperses. Even in Asia, it fruits sparingly, and propagates itself mainly by growth of its rhizome, forming colonies.

The branched, cylindrical, knobby rhizome is the thickness of a human finger and has numerous coarse fibrous roots below it. The exterior is brown and the interior white.[3][4][5]

Range and habitat[edit]

Sweet flag is native to India, central Asia, southern Russia and Siberia, and perhaps Eastern Europe. It also grows in China and Japan. It was introduced into Western Europe and North America for medicinal purposes. Habitats include edges of small lakes, ponds and rivers, marshes, swamps, and wetlands.[3][5]


In addition to "sweet flag" and "calamus" other common names include beewort, bitter pepper root, calamus root, flag root, gladdon, myrtle flag, myrtle grass, myrtle root, myrtle sedge, pine root, rat root, sea sedge, sweet cane, sweet cinnamon, sweet grass, sweet myrtle, sweet root, sweet rush, and sweet sedge.[2] Common names in Asia include: "Changpu 菖蒲" (Mandarin Chinese); "shoubu 菖蒲" (Japanese); "vacha"; "changpo 창포" (Korean); "bacch" (Unani); "bajai", "gora-bach", "vasa bach" (Hindi); "vekhand" (Marathi); "vasambu"/வசம்பு (Tamil); "vadaja", "vasa" (Telugu); "baje" (Kannada); "വയമ്പ്/vayambu" (Malayalam); Haimavati, "bhutanashini", "jatila" (Sanskrit), "kâmpean" កំពាន (Khmer), "bojho बोझो" (Nepali), and "Dlingo" (Indonesia).


The generic name is the Latin word acorus, which is derived from the Greek άχόρου (áchórou) of Dioscorides (note different versions of the text have different spellings). The word άχόρου itself is thought to have been derived from the word κόρη (kóri), which means pupil (of an eye), because of the juice from the root of the plant being used as a remedy in diseases of the eye ('darkening of the pupil').[6][7][8]

The specific name calamus (meaning "cane") is derived from Greek κάλαμος (kálamos, meaning "reed"), which is cognate to Latin culmus (meaning "stalk") and Old English healm (meaning "straw"), and derived from Proto-Indo European *kole-mo- (thought to mean "grass" or "reed"). The Arabic word قَلَم (qálam, meaning "pen") and Sanskrit कलम (kaláma, meaning "reed used as a pen", and a sort of rice) are thought to have been borrowed from Greek.[9][10][11][12]

The name "sweet flag" refers to its sweet scent and its similarity to Iris species, which are commonly known as flags in English since the late fourteenth century.[13][14]

Botanical information[edit]

Currently the taxonomic position of these forms is contested. The comprehensive taxonomic analysis in the Kew World Checklist of Selected Plant Families from 2002 considers all three forms to be distinct varieties of a single species.[15][16] Sue A. Thompson in her 1995 Ph.D. dissertation and in her 2000 entry in the Flora of North America considers the diploid form to be a distinct species. Thompson only analyses North American forms of the diploid variety in her treatment, and does not analyse the morphology of Asian forms of the diploid variety. Also, in older USA literature the name Acorus americanus may be used indiscriminately for all forms of Acorus calamus occurring in North America, irrespective of cytological diversity (i.e. both the diploid and triploid forms).[17] The recent treatment in the Flora of China from 2010, which is followed in the Tropicos database system, considers all varieties to be synonyms of a single taxonomically undifferentiated species, pointing to morphological overlap in the characteristics singled out by Thompson.[18][19]

According to Thompson the primary morphological distinction between the triploid and the North American forms of the diploid is made by the number of prominent leaf veins, the diploid having a single prominent midvein and on both sides of this equally raised secondary veins, the triploid having a single prominent midvein with the secondary veins barely distinct. Thompson notes a number of other details which she claims can be used to tell the different forms apart in North America, such as flower length, average maximum leaf length, relative length of the sympodial leaf with respect to the vegetative leaves, the average length of the spadix during flowering, and tendency of the leaf margin to undulate in the triploid. She notes that many of these characteristics overlap, but that in general the triploid is somewhat larger and more robust on average than most North American forms of the diploid. According to Heng Li, Guanghua Zhu and Josef Bogner in the Flora of China there is clear overlap in these characteristics and the different cytotypes are impossible to distinguish morphologically.[18][17]

Triploid plants are infertile and show an abortive ovary with a shrivelled appearance. This form will never form fruit (let alone seeds) and can only spread asexually.[17]

The tetraploid variety is usually known as Acorus calamus var. angustatus Besser. A number of synonyms are known, but a number are contested as to which variety they belong. It is morphologically diverse, with some forms having very broad and some narrow leaves. It is furthermore also cytotypically diverse, with an array of different karyotypes.[15][20][21]


A. calamus has been an item of trade in many cultures for thousands of years. It has been used medicinally for a wide variety of ailments, and its aroma makes calamus essential oil valued in the perfume industry. The essence from the rhizome is used as a flavor for pipe tobacco. When eaten in crystallized form, it is called "German ginger". In Europe Acorus calamus was often added to wine, and the root is also one of the possible ingredients of absinthe. It is also used in bitters. In Lithuania Ajeras (Sweet flag) is added to home baked black bread.


The Bible mentions its use in the holy anointing oil ( Exodus 30: 23). Although probably not native to Egypt, this plant was already mentioned in the Chester Beatty papyrus VI dating to approximately 1300 BC. The ancient Egyptians rarely mentioned the plant in medicinal contexts (the aforementioned papyrus mentioned using it in conjunction with several ingredients as a bandage used to soothe an ailment of the stomach), but it was certainly used to make perfumes.[22]

Initially, Europeans confused the identity and medicinal uses of the Acorus calamus of the Romans and Greeks with their native Iris pseudacorus. Thus the Herbarius zu Teutsch, published at Mainz in 1485, describes and includes a woodcut of this iris under the name Acorus. This German book is one of three possible sources for the French Le Grant Herbier, written in 1486, 1488, 1498 or 1508, of which an English translation was published as the Grete Herball by Peter Treveris in 1526, all containing the false identification of the Herbarius zu Teutsch.[23] William Turner, writing in 1538, describes 'acorum' as "gladon or a flag, a yelowe floure delyce".[24]

The plant was introduced to Britain in the late 16th century. By at least 1596 true Acorus calamus was grown in Britain, as it is listed in The Catalogue, a list of plants John Gerard grew in his garden at Holborn. Gerard notes "It prospereth exceeding well in my garden, but as yet beareth neither flowers nor stalke". Gerard lists the Latin name as Acorus verus, but it is evident there was still doubt about its veracity: in his 1597 herbal he lists the English common name as 'bastard calamus'.[25]

Cultural uses[edit]

In Britain the plant was cut for use as a sweet smelling floor covering for the packed earth floors of dwellings and churches, and stacks of rushes have been used as the centrepiece of rushbearing ceremonies for many hundreds of years.[26] It has also been used as a thatching material for English cottages.[27]

In modern Egypt it is thought to have aphrodisiac properties.[22]

For the Penobscot people this was a very important root. One story goes that a sickness was plaguing the people. A muskrat spirit came to a man in a dream, telling him that he (the muskrat) was a root and where to find him. The man awoke, found the root, and made a medicine which cured the people. In Penobscot homes, pieces of the dried root were strung together and hung up for preservation. Steaming it throughout the home was thought to "kill" sickness. While they were travelling, a piece of root was kept and chewed to ward off illness.[28]

Teton-Dakota warriors chewed the root to a paste, which they rubbed on their faces. It was thought to prevent excitement and fear when facing an enemy.[28]

On 5 May Japanese prepare a bath with hashōbu leaves (shōbu-yu) for children to promote good health and to ward off evil. In the Japanese calendar the day is known as Ayame no sekku (菖蒲の節句, the iris festival).

Illustration from an 1885 flora

Herbal medicine[edit]

Sweet flag has a very long history of medicinal use in Chinese and Indian herbal traditions.[29] The leaves, stems, and roots are used in various Siddha and Ayurvedic medicines[30] and by the Sikkim of Northeastern India.[31] Sweet flag is one of the most widely and frequently used herbal medicines among the Chipewyan people.[32] The Potawatomi people powdered the dried root and placed this up the nose for catarrh.[28]


This plant is sometimes used as a pond plant in horticulture.[33] There is at least one ornamental cultivar known; it is usually called 'Variegatus',[34] but the RHS recommends calling it 'Argenteostriatus'.[35]


Both triploid and tetraploid A. calamus contain alpha-asarone. Other phytochemicals include:

Diploids do not contain beta-asarone (β-asarone).[40]

Cultural symbolism[edit]

The calamus has long been a symbol of love. The name is associated with a Greek myth: Kalamos, son of the river-god Maeander, who loved the youth Karpos, of Zephyrus (the West Wind) and Chloris (Spring). When Karpos drowned in a swimming race, Kalamos also drowned and was transformed into a reed, whose rustling in the wind was interpreted as a sigh of lamentation.

The plant was a favorite of Henry David Thoreau (who called it "sweet flag"), and also of Walt Whitman, who added a section called the "Calamus" poems, to the third edition of Leaves of Grass (1860). In the poems the calamus is used as a symbol of love, lust, and affection. Lewis Carroll uses the plant in Through the Looking-Glass as a symbol of the fleeting nature of childhood: in the story, Alice picks scented rushes but complains that the prettiest ones are always just out of reach, while the ones she is able to reach fade and lose their scent as soon as they are plucked.

The root of the calamus (Tamil vasambu வசம்பு) is cut into disc-shaped beads, and made into bracelets, which are typically worn by newborns for the first few months. A vasambu bracelet is a symbol of a newborn baby in Tamil culture.

Safety and regulations[edit]

A. calamus and products derived from A. calamus (such as its oil) were banned from use as human food or as a food additive in 1968 by the United States Food and Drug Administration.[41] The FDA ban was the 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 calamus. The animals developed tumors, and the plant was labeled procarcinogenic.[42][43][unreliable source?] Wichtl says "It is not clear whether the observed carcinogenic effects in rats are relevant to the human organism."[44] However, most sources advise caution in ingesting strains other than the diploid strain.

The diploid strains of A. calamus in parts of Mongolia, in parts of the western Himalayas and C Siberia, and the Acorus americanus does not contain the procarcinogenic β-asarone.[38][45][verification needed][46]

In reality β-asarone is neither hepatotoxic nor directly hepatocarcinogenic. It must first undergo metabolic l'-hydroxylation in the liver before achieving toxicity. Cytochrome P450 in the hepatocytes is responsible for secreting the hydrolyzing enzymes that convert β-asarone into genotoxic epoxide structure.[47] Even with the activation of these metabolites, the carcinogenic potency is very low because of the rapid breakdown of epoxide residues with hydrolase which leaves these compounds inert.[48] Additionally, the major metabolite of β-asarone is 2,4,5-trimethoxycinnamic acid, a derivative which is not a carcinogen.[49]

Notes and references[edit]

  1. ^ Lansdown, R.V. (2014). "Acorus calamus". The IUCN Red List of Threatened Species. 2014: e.T168639A43116307. doi:10.2305/IUCN.UK.2014-1.RLTS.T168639A43116307.en. Retrieved 5 January 2018.
  2. ^ a b Sylvan T. Runkel; Alvin F. Bull (2009) [1979]. Wildflowers of Iowa Woodlands. Iowa City, Iowa: University of Iowa Press. p. 119. ISBN 9781587298844. Retrieved 13 December 2011.
  3. ^ a b Grieve, M. "Sedge, Sweet" in A Modern Herbal, accessed on 4.1.2017 at
  4. ^ Anonymous. "Sweet Flag" accessed on 4.1.2017 at
  5. ^ a b Anonymous. "Sweet Flag" accessed on 4.1.2017 at
  6. ^ Pliny the Elder. "100". Naturalis Historia [The Natural History]. 25 (in Latin).
  7. ^ Dioscorides, Pedanius (1829). "2". Περὶ ὕλης ἰατρικῆς [De Materia Medica] (in Greek). Translated by Sprengel, Karl Philipp. pp. 11, 50–70.
  8. ^ "Nomina generica, quae Characterem essentialem vel habitum plantae exhibent, optima sunt". Scientific Latin (in Latin). 14 October 2001.
  9. ^ "Monier Williams Sanskrit-English Dictionary". Cologne Digital Sanskrit Dictionaries.
  10. ^ Liddell, Henry George & Scott, Robert (1925). "κάλα^μος". A Greek-English Lexicon. Oxford University Press.
  11. ^ Harper, Douglas. "Shawm". Online Etymological Dictionary. Retrieved 9 July 2013.
  12. ^ Avadhani, Mythili; et al. (2013). "The Sweetness and Bitterness of Sweet Flag [Acorus calamus L.] – A Review" (PDF). Research Journal of Pharmaceutical, Biological and Chemical Sciences. 4 (2): 598. ISSN 0975-8585.
  13. ^ Harper, Douglas. "Flag". Online Etymological Dictionary.
  14. ^ "Acorus americanus – Sweet Flag". Rook.Org. 14 April 2004. Archived from the original on 25 August 2006.
  15. ^ a b Govaerts, R.; World Checklist of Selected Plant Families: Royal Botanic Gardens, Kew; 2002;; accessed 9 July 2013
  16. ^ The Plant List;; accessed 9 July 2013
  17. ^ a b c Thompson, Sue A.; Flora of North America, Acorus; 2000;
  18. ^ a b Heng, Li (李恒), Guanghua, Zhu (朱光华); and Bogner, Josef; Flora of China, Vol. 23, Acoraceae; Science Press & Missouri Botanical Garden; Beijing & St. Louis; 2010; accessed at
  19. ^ "Acorus calamus". Tropicos. Missouri Botanical Garden. Retrieved 9 July 2013.
  20. ^ Ogra, R. K.; et al. (10 December 2009). "Indian calamus (Acorus calamus L.): not a tetraploid" (PDF). Current Science. 97 (11).
  21. ^ Hong, Wang; Wenli, Li; Zhijian, Gu & Yongyan, Chen (2001). "Cytological study on Acorus L. in southwestern China, with some cytogeographical notes on A. calamus". Acta Botanica Sinica. 43 (4): 354–358.
  22. ^ a b Manniche, Lisa; An Ancient Egyptian Herbal, pg. 74; American University in Cairo Press; Cairo; 2006; ISBN 977 416 034 7
  23. ^ Rohde, Eleanour Sinclair; The Old English Herbals; Longmans, Green and Co.; 1922; accessed at
  24. ^ Turner, William; Libellus de re herbaria, pg. Aii; 1538; in Jackson, Benjamin Daydon; Libellus de re herbaria novus, by William Turner, originally pub. in 1538, reprinted in facsimile, pg. 36; private print; London; 1877; accessed at
  25. ^ Jackson, Benjamin Daydon (1876). A catalogue of plants cultivated in the garden of John Gerard. London: private printing. pp. 1, 23.
  26. ^ Hüsken, Wim N. M. (1996), "Rushbearing:a forgotten British custom", English parish drama, p. 17, ISBN 978-90-420-0060-5
  27. ^ Hirsch, Pamela; Gladstar, Rosemary (2000). Planting the future: saving our medicinal herbs. Rochester, Vt: Healing Arts Press. p. 85. ISBN 978-0-89281-894-5.
  28. ^ a b c Erichsen-Brown, Charlotte (1989). Medicinal and Other Uses of North American Plants: A Historical Survey with Special Reference to the Eastern Indian Tribes. Dover Publications. pp. 231–232. ISBN 978-0-486-25951-2.
  29. ^ Mukherjee P.K., Kumar V., Mal M., Houghton P.J. "Acorus calamus: Scientific validation of ayurvedic tradition from natural resources"Pharmaceutical Biology 2007 45:8 (651–666)
  30. ^ "Vasambu". 1 April 2013. Archived from the original on 14 August 2013.
  31. ^ O'Neill, Alexander; et al. (2017-03-29). "Integrating ethnobiological knowledge into biodiversity conservation in the Eastern Himalayas". Journal of Ethnobiology and Ethnomedicine. 13 (21): 21. doi:10.1186/s13002-017-0148-9. PMC 5372287. PMID 28356115.
  32. ^ Johnson, Derek; Linda Kershaw; Andy MacKinnon; Jim Pojar (1995). Plants of the Western Boreal Forest & Aspen Parkland. Lone Pine Publishing. ISBN 978-1-55105-058-4.
  33. ^ Oudhia, P. (2002). "Rice-Acorus intercropping: a new system developed by innovative farmers of Chhattisgarh (India)". International Rice Research Notes. 27 (1): 56. ISSN 0117-4185.
  34. ^ "Acorus calamus 'Variegatus'". Missouri Botanical Garden. Retrieved 9 July 2013.
  35. ^ "Acorus calamus 'Argenteostriatus'". Royal Horticultural Society. Retrieved 9 July 2013.
  36. ^ Streloke, M.; Ascher, K. R. S.; Schmidt, G. H.; Neumann, W. P.; et al. (1989). "Vapor pressure and volatility of β-asarone, the main ingredient of an indigenous stored-product insecticide, Acorus calamus oil". Phytoparasitica. 17 (4): 299–313. doi:10.1007/BF02980759.
  37. ^ Paneru, R.B.; Lepatourel, G; Kennedy, S; et al. (1997). "Toxicity of Acorus calamus rhizome powder from Eastern Nepal to Sitophilus granarius (L.) and Sitophilus oryzae (L.) (Coleoptera, Curculionidae)". Crop Protection. 16 (8): 759–763. doi:10.1016/S0261-2194(97)00056-2.
  38. ^ a b Marongiu, Bruno; Piras, Alessandra; Porcedda, Silvia; Scorciapino, Andrea (2005). "Chemical Composition of the Essential Oil and Supercritical CO
    Extract of Commiphora myrrha (Nees) Engl. and of Acorus calamus L.". Journal of Agricultural and Food Chemistry. 53 (20): 7939–7943. doi:10.1021/jf051100x. PMID 16190653.
  39. ^ Raina, V. K.; Srivastava, S. K.; Syamasunder, K. V.; et al. (2003). "Essential oil composition of Acorus calamus L. from the lower region of the Himalayas". Flavour and Fragrance Journal. 18 (1): 18–20. doi:10.1002/ffj.1136.
  40. ^ Radušienė, J; Judžentienė, A; Pečiulytė, D; Janulis, V (2007). "Essential oil composition and antimicrobial assay of Acorus calamus leaves from different wild populations". Plant Genetic Resources: Characterization and Utilization. 5: 37–44. doi:10.1017/S1479262107390928.
  41. ^ "Substances Generally Prohibited From Direct Addition or Use as Human Food: Calamus and its derivatives". Code of Federal Regulations, Title 21, Chapter I, Subchapter B, Part 189. Food and Drug Administration.
  42. ^ Weisburger, E.K. (1979). "Natural carcinogenic products". Environmental Science & Technology. 13 (3): 278–281. doi:10.1021/es60151a002.
  43. ^ "sweet flag / bitterroot – Acorus calamus, A. americanus". Jim McDonald ~Herbalist~.
  44. ^ Wichtl, Max, ed. (2004). Herbal Drugs and Phytopharmaceuticals: A Handbook for Practice on a Scientific Basis (3rd ed.). Medpharm: Scientific Publ. ISBN 978-3-8047-5027-2.
  45. ^ Rost, L.C.M.; Bos, R. (1979). "Biosystematic investigations with Acorus L., 3. Communication - constituents of essential oil". Planta Medica. 36 (4): 350–361. ISSN 0032-0943.
  46. ^ Phongpaichit, S.; Pujenjob, N.; Rukachaisirikul, V.; Ongsakul, M. (2005). "Antimicrobial activities of the crude methanol extract of Acorus calamus Linn" (PDF). Songklanakarin J. Sci. Technol. 27 (Suppl. 2): 517–523.
  47. ^ McGuffin, Michael, ed. (1997). American Herbal Products Association's Botanical Safety Handbook. Boca Raton, Florida: CRC Press. p. 135. ISBN 978-0-8493-1675-3.
  48. ^ Luo, G. A. N. G., MAZEN K. Qato, and THOMAS M. Guenthner. "Hydrolysis of the 2', 3'-allylic epoxides of allylbenzene, estragole, eugenol, and safrole by both microsomal and cytosolic epoxide hydrolases." Drug Metabolism and Disposition 20.3 (1992): 440-445.
  49. ^ Hasheminejad, G., and J. Caldwell. "Genotoxicity of the alkenylbenzenes α− and β-asarone, myristicin and elemicin as determined by the UDS assay in cultured rat hepatocytes." Food and Chemical Toxicology 32.3 (1994): 223-231.

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