Acorus calamus has diploid, triploid, and tetraploid forms. 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. These forms are sometimes treated as distinct species, at other times as a single variable species, and at other times are separated into three distinct forms of the species Acorus calamus. Because the medicinal benefits of each form potentially differ, we are following the treatment in the Kew 'World Checklist of Selected Plant Families' which treats it as a single species with three distinct forms[].
In practice, the non-medicinal uses of each form are identical, but we have included individual records for all the three varieties in this database to make it is easier to understand the potential differences in considerations regarding medicinal usage[].

Common Name: Sweet Flag

General Information

Sweet flag is a stemless herbaceous perennial plant producing a clump of sword-shaped leaves up to 150cm tall from an extensively-branched, creeping rhizome that is up to 3cm in diameter[].
Sweet flag is a multipurpose plant with a wide range of used as a medicine, food and source of materials. It has a long history of use as a medicinal and culinary plant, dating back 2,000 years or more, and has often been cultivated for this purpose, though it is more commonly allowed to naturalize and then be harvested from the wild. It is often grown as an ornamental[].

Known Hazards

The plant is found in three distinct forms, one diploid, one triploid and one tetraploid. Each of these forms has a distinct chemistry - in particular the make up of the essential oil differs considerably. The essential oil obtained from all of the forms contains asarone, which like any essential oil can be toxic in quite small quantities if ingested in its pure form. In addition, the asarone is found in two forms, alpha and beta. Research has shown that the beta form has potential carcinogenic and hepatotoxic effects upon the body if used in quantity. The diploid form of the species (found in parts of northern Asia and much of N. America) is free of beta-asarone, whilst the tetraploid form (found in central Asia, through India, Japan and tropical Asia) contains 90 - 95% beta asarone. The triploid form, found in Europe, southwest Asia to the Himalayas) contains a small percentage of beta-asarone[].
In practice, when the whole root is used medicinally, the plant is safe and beneficial to use - as is shown by the wide medicinal use of the plant in Asia, where they use the form that is rich in beta-asarone[, ].

Botanical References

,

Range

Widely spread from the Caucasus through western Asia and Siberia to China, India and southeast Asia. Much of N. America. Widely naturalized elsewhere.

Habitat

Found in moist soils and shallow water in ditches, marshes, river edges and ponds[, , , ].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Perennial
Height	1.00 m
Pollinators	Insects
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Sweet flag is a widespread plant that can be found from the cold temperate zone right through to the tropics. It is tolerant of a wide range of environmental conditions, though it grows best in areas where annual daytime temperatures are within the range 18 - 26°c, and can tolerate 4 - 30°c[]. When dormant, the plant can survive temperatures down to about -25°c[, ]. It prefers a mean annual rainfall in the range 700 - 2,000mm, but tolerates 430 - 4,200mm[].
Succeeds in a wide range of soils, requiring a position in shallow water or in a very moist loamy soil[]. Requires a sunny position[]. Prefers a pH in the range 5.5 to 6.5, tolerating 5 - 7.5[].
The plant never sets seed unless it is growing in water[]. It can spread quite freely at the roots and soon becomes established.

Edible Uses

The rhizome is candied and made into a sweetmeat[, , , , , , ]. It can be peeled and washed to remove the bitterness and then eaten raw like a fruit[, ]. It makes a palatable vegetable when roasted[] and can also be used as a flavouring[]. Rich in starch, the root contains about 1% of an essential oil that is used as a food flavouring[, , ]. The root also contains a bitter glycoside[]. 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[, , , , ]. A pinch of the powdered rhizome is used as a flavouring in tea[].

The young and tender inflorescence is often eaten by children for its sweetness[].

Young leaves - cooked[]. The fresh leaves contain 0.078% oxalic acid[]. The leaves can be used to flavour custards in the same way as vanilla pods[].

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

Medicinal

See the individual records for each of the three varieties of Acorus calamus for more information on their medicinal uses and potential health disbenefits[].
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[]. In Ayurveda it is highly valued as a rejuvenator for the brain and nervous system and as a remedy for digestive disorders[].
The plant is found in three distinct forms, one diploid, one triploid and one tetraploid. Each of these forms has a distinct chemistry and the tetraploid form is particularly rich in beta-asarone, a compound that has potential health disbenefits. See notes above on toxicity for more information[, ].
In practice, when the whole root is used medicinally, the plant is safe and beneficial to use - as is shown by the wide medicinal use of the plant in Asia, where they use the form that is rich in beta-asarone[, ].

The root is anodyne, aphrodisiac, aromatic, carminative, diaphoretic, emmenagogue, expectorant, febrifuge, hallucinogenic, hypotensive, sedative, stimulant, stomachic, mildly tonic and vermifuge[, , , , , , , , ]. It is used internally in the treatment of digestive complaints, bronchitis, sinusitis etc[]. 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[] and it is, therefore, recommended in the treatment of anorexia nervosa[]. However if the dose is too large it will cause nausea and vomiting[]. It is a folk remedy for arthritis, cancer, convulsions, diarrhoea, dyspepsia, epilepsy etc[]. An infusion of the root can bring about an abortion[] whilst chewing the root alleviates toothache[]. Chewing the root is also said to kill the taste for tobacco[].
Sweet flag is also used externally to treat skin eruptions, rheumatic pains and neuralgia[].
Roots 2 - 3 years old are used since older roots tend to become tough and hollow[]. They are harvested in late autumn or early spring and are dried for later use[]. The dry root loses 70% of its weight, but has an improved smell and taste[]. It does, however, deteriorate if stored for too long[].

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[]. Chewing large amounts of the leaves and/or roots can cause hallucinations due to the presence of asarones, which have mescaline-like hallucinogenic properties if taken in sufficient quantities[]. See also the notes above on toxicity.

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

Other Uses

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

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

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

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 cool temperate areas[, ].
Division in spring just before growth starts[]. Very easy, it can be carried out successfully at any time in the growing season and can be planted direct into its permanent positions[].