Acorus calamus

Acorus calamus (also called sweet flag, sway or muskrat root, among many other common names) is a species of flowering plant with psychoactive chemicals. It is a tall wetland monocot of the family Acoraceae, in the genus Acorus. Although used in traditional medicine over centuries to treat digestive disorders and pain, it has no clinical evidence of safety or efficacy and may be toxic if ingested, and so has been commercially banned for use in food in the United States.

Description

A shrub or small tree. It grows 5 m tall. There are prickles along the stem. The leaves are twice divided and there are 8-18 pairs of pinnae. There are up to 50 pairs of pinnules on each pinnae. The flowers are yellow. They are in large clusters at the ends of branches. The pods are flattened.

Edible Uses

The rhizome can be candied into a sweetmeat, peeled and washed to reduce bitterness and eaten raw like a fruit, roasted as a vegetable, or used as a flavouring. It is rich in starch and contains about 1% essential oil used in food flavouring, as well as a bitter glycoside. The dried, powdered rhizome has a spicy flavour and substitutes for ginger, cinnamon, and nutmeg; a pinch can flavour tea. Young leaves are cooked and can also flavour custards in the same way as vanilla pods — the fresh leaves contain 0.078% oxalic acid. The inner portion of young stems is eaten raw and makes a palatable salad. The young, tender inflorescence is often eaten by children for its sweetness. Some caution is advised regarding toxicity.

Traditional Uses

The underground stems are ground and used to flavour food. They can be eaten raw. They have a gingery peppery taste. It should probably only be eaten sparingly with caution. They contain a bitter glucoside called acorin. The forms of Acorus in Asia contain a chemical called asarone which causes cancer. The centre of the above ground section can be eaten. The underground stem can be washed, peeled, chopped into 1 cm long pieces and cooked for 20 minutes with several changes of water then simmered for 20 minutes in sugar syrup to produce candy.

Medicinal Uses

Sweet flag has a long history of medicinal use across many traditions and is widely used today as an aromatic stimulant and mild tonic. In Ayurveda it is valued as a brain and nervous system rejuvenator and a remedy for digestive disorders, though some forms may be carcinogenic — see toxicity notes. The root is anodyne, aphrodisiac, aromatic, carminative, diaphoretic, emmenagogue, expectorant, febrifuge, hallucinogenic, hypotensive, sedative, stimulant, stomachic, mildly tonic, and vermifuge. Internally it treats digestive complaints, bronchitis, and sinusitis, and is said to stimulate and normalize appetite. In small doses it reduces stomach acidity; larger doses increase stomach secretions, making it useful in treating anorexia nervosa — though excessive doses cause nausea and vomiting. Externally it treats skin eruptions, rheumatic pains, and neuralgia. An infusion of the root can induce abortion, and chewing the root relieves toothache and is said to kill the taste for tobacco. It is a folk remedy for arthritis, cancer, convulsions, diarrhoea, dyspepsia, and epilepsy. Roots 2–3 years old are preferred, as older roots become tough and hollow. They are harvested in late autumn or early spring and dried for later use — the dry root loses 70% of its weight but gains in smell and taste, though it deteriorates with prolonged storage. Caution is advised, especially with the distilled essential oil, as large doses can cause mild hallucinations. A homeopathic remedy made from the roots treats flatulence, dyspepsia, anorexia, and gall bladder disorders. Bath oils containing calamus have caused erythema and dermatitis, particularly in hypersensitive individuals.

Known Hazards

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. Although limits on consumption in food or alcoholic beverages (115 micrograms per day) were recommended in a 2001 ruling by the European Commission, the degree of safe exposure remained undefined. Although calamus has been used for its fragrance and ingested, it has not been studied by rigorous clinical research. Individual medical reports of toxicity mention severe nausea and prolonged vomiting over many hours following oral uses. Laboratory studies of its extracts indicate other forms of toxicity, due mainly to the emetic compound β-asarone. Allegedly, the plant is psychoactive (hallucinogenic), but for example all experiments with American calamus have been completely unsuccessful, even those involving very high dosages (up to 300 g of rhizomes).

Distribution

Its natural range is the warm temperate regions of Iran and India. They are found throughout the Philippines both cultivated and wild, growing in swamps. In Papua New Guinea it grows from sea level to 2600 m altitude. It can tolerate frost but cannot tolerate drought. It normally occurs in ditches, swamps, and on the edges of lakes and streams. It grows in wetland. It grows best in water no deeper than 22 cm. Often the plant grows in dense pure stands. It is mostly in places with a temperature below 20°C. It suits hardiness zones 3-10.

Where It Grows

Afghanistan, Armenia, Asia, Australia, Austria, Balkans, Bangladesh, Belarus, Bhutan, Bosnia, Brazil, Britain, Canada, Caucasus, China, Czech Republic, Denmark, Egypt, Estonia, Europe, France, Germany, Himalayas, Hungary, India, Indochina, Indonesia, Iran, Ireland, Italy, Japan, Korea, Laos, Latvia, Lithuania, Luxembourg, Macedonia, Malaysia, Maldives, Mediterranean, Middle East, Mongolia, Myanmar, Nepal, Netherlands, New Zealand, North Africa, North America, Northeastern India, Pacific, Pakistan, Papua New Guinea, PNG, Philippines, Philippines, Poland, Russia, Scandinavia, SE Asia, Serbia, Siberia, Sikkim, Slovenia, South America, Spain, Sri Lanka, Sweden, Thailand, Turkey, Türkiye, Ukraine, USA, Vietnam, Yugoslavia,

Cultivation

Prefers growing in shallow water or in a very moist loamy soil. Requires a sunny position. Prefers a pH in the range 5.5 to 7.5. Plants are hardy to about -25°c. 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. It can spread quite freely at the roots however and soon becomes established. The rhizomes are typically harvested when the plant matures in late summer to autumn. Sweet Flag flowers from late spring to early summer. Sweet Flag is a moderate grower, establishing quickly in suitable moist environments and forming dense stands over time.

Propagation

Seed is best sown in a cold frame as soon as it is ripe, with the pot stood in about 3cm of water. Pot up seedlings as soon as they are large enough to handle, keep them wet by standing pots in shallow water, and overwinter in a greenhouse or cold frame during the first year. Seed is rarely produced in Britain. Division in spring just before growth begins is very easy and can be carried out successfully at any time during the growing season, planting directly into permanent positions.

Other Uses

The leaves are used in basket making, woven into mats, and have been used as roof thatch. The plant is used in wetland restoration and as a natural water filter in aquatic systems, where its dense growth provides wildlife habitat and improves soil stability. An essential oil from the rhizome is used in perfumery and food flavouring; it is concentrated mainly in the outer skin of the root and has a fragrance reminiscent of patchouli oil. Fresh roots yield about 1.5–3.5% essential oil; dried roots yield about 0.8%, while some Japanese plants have yielded 5%. The essential oil also acts as an insect repellent and insecticide, effective against houseflies. When added to rice in granaries it significantly reduces insect damage by sterilizing male rice weevils. An essential oil from the leaves is used in perfumery and for making aromatic vinegar. The leaves and root have a refreshing scent of cinnamon. All parts of the plant can be dried to repel insects or scent linen cupboards, burned as incense, or used as a strewing herb. The growing plant is said to repel mosquitoes. The dense foliage provides shelter for invertebrates and overwintering sites for beneficial insects. The aromatic rhizomes may help mask the scent of other plants and confuse some pests.

Production

Tender young stalks are harvested. The young underground stem needs to be separated from the roots and pulled or dug out.

Other Information

It is sold in local markets. It is not known if it is used for food in Papua New Guinea.

Notes

1% volatile oil; a bitter glucoside - acorin; There is only one genus in the Acoraceae. There are 2-4 Acorus species. It has a long history of use for perfume and medicine.

Synonyms

Also Known As

Airi, Ajer, Ajeras, Aleras, Ayer, Bach, Baghshtak, Baje gida, Bas, Boch, Bojho, Bos, Changpu, Flagroot, Fortunate bullrush, Huvagoh, Jagier, Jaringao, Jeringau, Kalmos, Kalmus, Khnkegheg, Lepiech, Lin-lay, Lin-ne, Lubigan, Myrtle flag, Pravi kolmež, Puskvorec obecny, Sweet cane, Sweet sedge, Tatarak. Vacha, Vasa, Vasambu, Vavambu, Vayambu, Vekhand, Wan nam

References (70)

• Ambasta S.P. (Ed.), 2000, The Useful Plants of India. CSIR India. p 11
• Aryal, K. P., et al, 2018, Diversity and use of wild and non-cultivated edible plants in the Western Himalaya. Journal of Ethnobiology and Ethnomedicine (2018) 14:10
• Baro, D., Baruah, S. and Borthukar, S. K. 2015, Documentation on wild vegetables of Baksa district, BTAD (Assam). Scholars Research Library. Archives of Applied Science Research, 2015, 7 (9):19-27
• Beckstrom-Sternberg, Stephen M., and James A. Duke. "The Foodplant Database." http://probe.nalusda.gov:8300/cgi-bin/browse/foodplantdb.(ACEDB version 4.0 - data version July 1994)
• Behera, K. K. et al, 2008, Wild Edible Plants of Mayurbhanj District, Orissa, India. J. Econ. Taxon. Bot. Vol. 32 (Suppl,) pp 305-314

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