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Toxic parts

The fresh root can be poisonous[1]. When using the plant medicinally, the isolated essential oil should not be used[2]. 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[3][4]. 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[3][4]. 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[5].

Edible uses


The rhizome is candied and made into a sweetmeat[6][7][8][9][10][11][12]. It can be peeled and washed to remove the bitterness and then eaten raw like a fruit[13][14]. It makes a palatable vegetable when roasted[15] and can also be used as a flavouring[16]. Rich in starch, the root contains about 1% of an essential oil that is used as a food flavouring[17][8][18]. The root also contains a bitter glycoside[14]. 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[7][9][19][20][12]. A pinch of the powdered rhizome is used as a flovouring in tea[21]. The young and tender inflorescence is often eaten by children for its sweetness[7]. Young leaves - cooked[9]. The fresh leaves contain 0.078% oxalic acid[22]. The leaves can be used to flavour custards in the same way as vanilla pods[23].

The inner portion of young stems is eaten raw[10]. It makes a very palatable salad[12].

Unknown part


Material uses

The leaves are used in basket making or woven into mats[24]. They have also been used as a thatch for roofs[7].

An essential oil from the rhizome is used in perfumery and as a food flavouring[17][8][18]. The oil is contained mainly in the outer skin of the root[25], it has a fragrance reminiscent of patchouli oil[15]. The fresh roots yield about 1.5 - 3.5% essential oil, dried roots about 0.8%[7][22]. Some plants from Japan have yielded 5% essential oil[7]. The essential oil is also an insect repellent and insecticide[3][21]. It is effective against houseflies[22]. 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[23]. An essential oil obtained from the leaves is used in perfumery and for making aromatic vinegars[25].

The leaves and the root have a refreshing scent of cinnamon[25]. All parts of plant can be dried and used to repel insects or to scent linen cupboards[26][27][16]. They can also be burnt as an incense[27], whilst the whole plant was formerly used as a strewing herb[7][27][11][4]. The growing plant is said to repel mosquitoes[28][29].

Medicinal uses(Warning!)

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[7]. In Ayurveda it is highly valued as a rejuvenator for the brain and nervous system and as a remedy for digestive disorders[5]. 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[7][1][30][31][32][2][33][22][34]. It is used internally in the treatment of digestive complaints, bronchitis, sinusitis etc[4]. 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[5] and it is, therefore, recommended in the treatment of anorexia nervosa[23]. 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[4]. An infusion of the root can bring about an abortion[33] whilst chewing the root alleviates toothache[33]. It is a folk remedy for arthritis, cancer, convulsions, diarrhoea, dyspepsia, epilepsy etc. Chewing the root is said to kill the taste for tobacco[3]. Roots 2 - 3 years old are used since older roots tend to become tough and hollow[7]. They are harvested in late autumn or early spring and are dried for later use[7]. The dry root loses 70% of its weight, but has an improved smell and taste[23]. It does, however, deteriorate if stored for too long[23]. 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[15]. See also the notes above on toxicity.

A homeopathic remedy is made from the roots[30]. It is used in the treatment of flatulence, dyspepsia, anorexia and disorders of the gall bladder[30].


Ecosystem niche/layer

Ecological Functions

Nothing listed.


Nothing listed.


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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[7][35]. Division in spring just before growth starts[17]. 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].

Practical Plants is currently lacking information on propagation instructions of Acorus calamus. Help us fill in the blanks! Edit this page to add your knowledge.


Prefers growing in shallow water or in a very moist loamy soil[36]. Requires a sunny position[36]. Prefers a pH in the range 5.5 to 7.5.

Plants are hardy to about -25°c[37]. 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[7]. It can spread quite freely at the roots however and soon becomes established.


Problems, pests & diseases

Associations & Interactions

There are no interactions listed for Acorus calamus. Do you know of an interaction that should be listed here? edit this page to add it.

Polycultures & Guilds

There are no polycultures listed which include Acorus calamus.




None listed.


None listed.

Full Data

This table shows all the data stored for this plant.

Binomial name
Acorus calamus
Imported References
Edible uses
None listed.
Material uses
None listed.
Medicinal uses
None listed.
Functions & Nature
Provides forage for
Provides shelter for
Hardiness Zone
Heat Zone
full sun
no shade
Soil PH
Soil Texture
Soil Water Retention
Environmental Tolerances
    Native Climate Zones
    None listed.
    Adapted Climate Zones
    None listed.
    Native Geographical Range
    None listed.
    Native Environment
    None listed.
    Ecosystem Niche
    None listed.
    Root Zone Tendancy
    None listed.
    Deciduous or Evergreen
    Herbaceous or Woody
    Life Cycle
    Growth Rate
    Mature Size
    1 x 1 meters
    Flower Colour
    Flower Type

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    2. ? Mills. S. Y. The Dictionary of Modern Herbalism. ()
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    5. ? Chevallier. A. The Encyclopedia of Medicinal Plants Dorling Kindersley. London ISBN 9-780751-303148 (1996-00-00)
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    18. ? Schery. R. W. Plants for Man. ()
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    28. ? 28.028.1 Riotte. L. Companion Planting for Successful Gardening. Garden Way, Vermont, USA. ISBN 0-88266-064-0 (1978-00-00)
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