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Acorus calamus - L.

Common Name Sweet Flag - Calamus
Family Araceae
USDA hardiness 4-11
Known Hazards The fresh root can be poisonous[7]. When using the plant medicinally, the isolated essential oil should not be used[165]. The essential oil in the roots of some populations of this plant contains the compound asarone. This has tranquillising and antibiotic activity, but is also potentially toxic and carcinogenic[218, 238]. It seems that these compounds are found in the triploid form of the species (found in Asia) whilst the diploid form (found in N. America and Siberia) is free of the compounds[218, 238]. However, the root (but not the isolated essential oil) has been used in India for thousands of years without reports of cancer which suggests that using the whole herb is completely safe, though more research is needed[254]. Only roots free from or with a low content of beta asarone should be used in human herb therapy. Should be avoided in patients taking monoamine oxidase inhibitor antidepressants as possible side-effects [301].
Habitats Found in moist soils and shallow water in ditches, marshes, river edges and ponds[1, 100, 187, 244].
Range Europe, Asia and N. America. Naturalized in Britain[17].
Edibility Rating    (3 of 5)
Other Uses    (4 of 5)
Weed Potential No
Medicinal Rating    (4 of 5)
Care (info)
Fully Hardy Wet Soil Water Plants Full sun
Acorus calamus Sweet Flag - Calamus

Acorus calamus Sweet Flag - Calamus


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Bloom Color: Green. Main Bloom Time: Mid summer. Form: Spreading or horizontal, Upright or erect.

Physical Characteristics

 icon of manicon of flower
Acorus calamus is a PERENNIAL growing to 1 m (3ft 3in) by 1 m (3ft 3in) at a medium rate.
See above for USDA hardiness. It is hardy to UK zone 3 and is not frost tender. It is in flower from May to July, and the seeds ripen from July to August. The species is hermaphrodite (has both male and female organs) and is pollinated by Insects.
Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It cannot grow in the shade. It prefers wet soil and can grow in water.

UK Hardiness Map US Hardiness Map


Calamus aromaticus

Plant Habitats

 Pond; Bog Garden;

Edible Uses

Edible Parts: Leaves  Root  Stem
Edible Uses: Condiment

The rhizome is candied and made into a sweetmeat[2, 4, 13, 55, 62, 115, 183]. It can be peeled and washed to remove the bitterness and then eaten raw like a fruit[106, 179]. It makes a palatable vegetable when roasted[192] and can also be used as a flavouring[61]. Rich in starch, the root contains about 1% of an essential oil that is used as a food flavouring[1, 13, 57]. The root also contains a bitter glycoside[179]. Some caution is advised, see the notes above on toxicity. The dried and powdered rhizome has a spicy flavour and is used as a substitute for ginger, cinnamon and nutmeg[4, 55, 142, 177, 183]. A pinch of the powdered rhizome is used as a flovouring in tea[272]. The young and tender inflorescence is often eaten by children for its sweetness[4]. Young leaves - cooked[55]. The fresh leaves contain 0.078% oxalic acid[240]. The leaves can be used to flavour custards in the same way as vanilla pods[244]. The inner portion of young stems is eaten raw[62]. It makes a very palatable salad[183].

References   More on Edible Uses

Medicinal Uses

Plants For A Future can not take any responsibility for any adverse effects from the use of plants. Always seek advice from a professional before using a plant medicinally.
Abortifacient  Anodyne  Antirheumatic  Aphrodisiac  Aromatic  Carminative  Diaphoretic  Emmenagogue  
Epilepsy  Febrifuge  Hallucinogenic  Homeopathy  Odontalgic  Sedative  Stimulant  
Stomachic  Tonic  Vermifuge

Sweet flag has a very long history of medicinal use in many herbal traditions. It is widely employed in modern herbal medicine as an aromatic stimulant and mild tonic[4]. In Ayurveda it is highly valued as a rejuvenator for the brain and nervous system and as a remedy for digestive disorders[254]. However, some care should be taken in its use since some forms of the plant might be carcinogenic - see the notes above on toxicity for more information. The root is anodyne, aphrodisiac, aromatic, carminative, diaphoretic, emmenagogue, expectorant, febrifuge, hallucinogenic, hypotensive, sedative, stimulant, stomachic, mildly tonic and vermifuge[4, 7, 9, 21, 147, 165, 213, 240, 279]. It is used internally in the treatment of digestive complaints, bronchitis, sinusitis etc[238]. It is said to have wonderfully tonic powers of stimulating and normalizing the appetite. In small doses it reduces stomach acidity whilst larger doses increase stomach secretions[254] and it is, therefore, recommended in the treatment of anorexia nervosa[244]. However if the dose is too large it will cause nausea and vomiting[K]. Sweet flag is also used externally to treat skin eruptions, rheumatic pains and neuralgia[238]. An infusion of the root can bring about an abortion[213] whilst chewing the root alleviates toothache[213]. It is a folk remedy for arthritis, cancer, convulsions, diarrhoea, dyspepsia, epilepsy etc. Chewing the root is said to kill the taste for tobacco[218]. Roots 2 - 3 years old are used since older roots tend to become tough and hollow[4]. They are harvested in late autumn or early spring and are dried for later use[4]. The dry root loses 70% of its weight, but has an improved smell and taste[244]. It does, however, deteriorate if stored for too long[244]. Caution is advised on the use of this root, especially in the form of the distilled essential oil, since large doses can cause mild hallucinations[192]. See also the notes above on toxicity. A homeopathic remedy is made from the roots[9]. It is used in the treatment of flatulence, dyspepsia, anorexia and disorders of the gall bladder[9]. Bath oils containing calamus have caused redness of the skin (erythema) and dermatitis, particularly in hypersensitive individuals [301].

References   More on Medicinal Uses

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Other Uses

Basketry  Incense  Insecticide  Repellent  Strewing  Thatching  Weaving

The leaves are used in basket making or woven into mats[169]. They have also been used as a thatch for roofs[4]. An essential oil from the rhizome is used in perfumery and as a food flavouring[1, 13, 57]. The oil is contained mainly in the outer skin of the root[245], it has a fragrance reminiscent of patchouli oil[192]. The fresh roots yield about 1.5 - 3.5% essential oil, dried roots about 0.8%[4, 240]. Some plants from Japan have yielded 5% essential oil[4]. The essential oil is also an insect repellent and insecticide[218, 272]. It is effective against houseflies[240]. When added to rice being stored in granaries it has significantly reduced loss caused by insect damage because the oil in the root has sterilized the male rice weevils[244]. An essential oil obtained from the leaves is used in perfumery and for making aromatic vinegars[245]. The leaves and the root have a refreshing scent of cinnamon[245]. All parts of plant can be dried and used to repel insects or to scent linen cupboards[8, 14, 61]. They can also be burnt as an incense[14], whilst the whole plant was formerly used as a strewing herb[4, 14, 115, 238]. The growing plant is said to repel mosquitoes[20, 201].

Special Uses

Scented Plants

References   More on Other Uses

Cultivation details

Landscape Uses:Container, Ground cover, Massing, Rock garden, Seashore. Prefers growing in shallow water or in a very moist loamy soil[200]. Requires a sunny position[200]. Prefers a pH in the range 5.5 to 7.5. Plants are hardy to about -25°c[187]. The sweet flag has a long history of use as a medicinal and culinary plant. It has been cultivated for this purpose but was more commonly allowed to naturalize and was then harvested from the wild. The plant seldom flowers or sets seed in Britain and never does so unless it is growing in water[4]. It can spread quite freely at the roots however and soon becomes established. Special Features: Attractive foliage, North American native, Edible, Fragrant foliage, Naturalizing, Wetlands plant, Inconspicuous flowers or blooms.

References   Carbon Farming Information and Carbon Sequestration Information

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Plant Propagation

Seed - best sown in a cold frame as soon as it is ripe. Stand the pot in about 3cm of water. Pot up young seedlings as soon as they are large enough to handle, keep them wet by standing the pots in shallow water and overwinter for the first year in a greenhouse or cold frame. Seed is rarely produced in Britain[4, 17]. Division in spring just before growth starts[1]. Very easy, it can be carried out successfully at any time in the growing season and can be planted direct into its permanent positions[K].

Other Names

If available other names are mentioned here

Ajer, Ayer, Bach, Baje gida, Bas, Boch, Bojho, Bos, Cálamo, Changpu, Flagroot, Fortunate bullrush, Huvagoh, Jaringao, Jeringau, Kalmos, Kalmus, Lepiech, Lin-lay, Lin-ne, Lubigan, Myrtle flag, Pravi kolmež, Puskvorec obecny, Sweet cane, Sweet sedge, Vacha, Vasa, Vasambu, Vavambu, Vayambu, Vekhand, Wan nam [1-4].

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Found In

Countries where the plant has been found are listed here if the information is available

Native to: Alaska, Alberta, Altay, Amur, Assam, Bangladesh, Borneo, British Columbia, Buryatiya, Cambodia, China North-Central, China South-Central, China Southeast, Chita, Connecticut, East Himalaya, Hainan, Idaho, India, Inner Mongolia, Iowa, Irkutsk, Japan, Jawa, Kamchatka, Kansas, Kazakhstan, Khabarovsk, Kirgizstan, Korea, Krasnoyarsk, Kuril Is., Laccadive Is., Lesser Sunda Is., Maine, Malaya, Maldives, Manchuria, Manitoba, Massachusetts, Michigan, Minnesota, Mongolia, Montana, Myanmar, Nebraska, Nepal, New Brunswick, New Hampshire, New York, Newfoundland, Northwest Territorie, Nova Scotia, Ohio, Ontario, Pennsylvania, Philippines, Primorye, Prince Edward I., Qinghai, Québec, Sakhalin, Saskatchewan, South Dakota, Sri Lanka, Sulawesi, Thailand, Tibet, Tuva, Uzbekistan, Vermont, Vietnam, Washington, West Himalaya, West Siberia, Wisconsin, Xinjiang, Yakutskiya. Extinct in: District of Columbia, Illinois, Indiana, New Jersey, North Dakota, Rhode I., Virginia. Introduced into: Alabama, Albania, Andaman Is., Arkansas, Austria, Baltic States, Belarus, Belgium, Bulgaria, California, Cape Provinces, Central European Rus, Colorado, Czechoslovakia, Delaware, Denmark, East European Russia, Finland, France, Free State, Føroyar, Georgia, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Kentucky, Krym, Louisiana, Maryland, Mississippi, Missouri, Netherlands, New Guinea, North Carolina, North Caucasus, North European Russi, Northwest European R, Norway, Oklahoma, Oregon, Pakistan, Poland, Romania, Sicilia, South Carolina, South European Russi, Svalbard, Sweden, Switzerland, Tennessee, Texas, Transcaucasus, Turkey, Turkey-in-Europe, Ukraine, West Virginia, Yugoslavia

Weed Potential

Right plant wrong place. We are currently updating this section. Please note that a plant may be invasive in one area but may not in your area so it’s worth checking.

Conservation Status

IUCN Red List of Threatened Plants Status :

Related Plants
Latin NameCommon NameHabitHeightHardinessGrowthSoilShadeMoistureEdibleMedicinalOther
Acorus gramineusGrass-leaved Sweet Rush, Japanese Sweet Flag, Dwarf Sweet FlagPerennial0.3 6-10  LMHNMWeWa333
Iris pseudacorusYellow Flag, Paleyellow irisPerennial1.5 5-8 MLMSNMWeWa122

Growth: S = slow M = medium F = fast. Soil: L = light (sandy) M = medium H = heavy (clay). pH: A = acid N = neutral B = basic (alkaline). Shade: F = full shade S = semi-shade N = no shade. Moisture: D = dry M = Moist We = wet Wa = water.


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Readers comment

david Nicholls   Mon Mar 5 10:14:17 2001

I tried using the root to quit smoking after also reading in "A modern Herbal" that it is used when Peruvian Bark fails, Peruvian bark containing quinine, the active ingredient in the best quit smoking aid (for me personally), Nicobrevin. Maybe many things for fever have potential as quit smoking aids.

I'm sure it did eliminate the desire for a smoke, didn't have one for 2 hours, one every 15 mins being my usual, had about 4mm-6mm sqaure of root , then also tried about the same of rhizome, taste the same(Potters say the rhiozme is often called the root so I tried both) same effect (obviously this is only vaugely scientific).

After finding I had to keep taking it every few hours I decided I was not prepared to take such large amounts for fear of hallucinations or other risks, maybe worth researhing, I hope & think no one could patent the idea with it's folk history, so pharmaceutical corporations probably wouldn't bother with it.

Note: I can't recommend it to anyone as safe.

T. Matin   Sat Feb 16 2008

The rumor that this plant is toxic was propogated by a lab 'study' done (I think by or for the FDA) where huge amounts of Calamus was given to rats for extended periods of time. The rats grew tumors. It is perfectly safe to: A. Take a relatively large dose over a short period or B. Take a relatively small dose over a longer period of time. In general, the rule is to start with a small amount in order to aclimate yourself (and the plant) to each other. Hallucinations, if they happen, will probably not kill you, they may in fact teach you something if you just relax and take them for what they are. But I do not consider this plant as primarily a 'hallucinogen', it is of great medicinal value. But you have to trust it if you want your organism to benefit.

dr yogesh kumar   Tue Mar 18 2008

i want to know more in acorus its scientific reaserch on children ,good collectionof knowledge

Dian Rakhmawati Harsono   Sat Jun 20 2009

I've never been known abaut Acorus calamus, I'm not sure, its plant are in my country, Indonesia. Can You tell me, what is Indonesian called on Acorus calamus. Thank you

frann leach   Thu Oct 15 2009

US Food and Drug Administration Code of Federal Regulations Title 21 Regulations prohibiting the use of this plant or its extracts in the US

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