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
thumb|Inflorescence
Sweet flag is a herbaceous perennial, tall.
Only plants that grow in water bear flowers. The fruit is a berry filled with mucus, which when ripe falls into the water and disperses by floating. 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 Araceae, 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.
Range and habitat
Sweet flag is native to the Irtysh River valley in Kazakhstan, but has been widely introduced worldwide. Habitats include edges of small lakes, ponds and rivers, marshes, swamps, and other wetlands.
Names and etymology
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, sea sedge, sweet cane, sweet cinnamon, sweet grass, sweet myrtle, sweet root, sweet rush, sweet sedge and wada kaha.
The specific name calamus is derived from Greek κάλαμος (kálamos, meaning "reed"), cognate to Latin culmus ("stalk") and Old English healm ("straw"), Arabic قَلَم (qálam, "pen"), in turn from Proto-Indo European *kole-mo- (thought to mean "grass" or "reed"). The name "sweet flag" refers to its sweet scent and its similarity to Iris species, which have been commonly known as flags in English since at least the late fourteenth century.
History
The 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, but it was certainly used to make perfumes.
One of the ingredients in holy anointing oil, meaning "spiced cane" or "sweet cane", is identified by Robert Sturtevant and Butler Stanton as Acorus calamus. However, botanists such as James A. Duke and Harold Norman Moldenke reject this as it did not grow in Ancient Israel. William Turner, writing in 1538, describes 'acorum' as "gladon or a flag, a yelowe floure delyce".
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'. Carl O. Sauer reported that the tuber was already being used by North American Indians at the time of European contact.
Taxonomy
thumb|right|Illustration from an 1885 flora by [[Walther Otto Müller]]
There are three cytotypic forms distinguished by chromosome number: a diploid form (2n=24), an infertile triploid form (2n=36), and a tetraploid form (see below). The triploid form is the most common and is thought to have arisen relatively recently in the Himalayan region through hybridisation of the diploid with the tetraploid. The tetraploid form Acorus calamus var. angustatus is native throughout Asia, from India to Japan and the Philippines and from Indonesia to Siberia.
Chemistry
Calamus leaves and rhizomes contain a volatile oil that gives a characteristic odor and flavor. Diploids do not contain beta-asarone. 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.
Toxicity
Although calamus has been used for its fragrance and ingested, it has not been studied by rigorous clinical research.
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).
Uses
A. calamus has been an item of trade in many cultures for centuries. It has been used in traditional medicine for various ailments, and the aroma of its essential oil is used in the perfume industry.
Food
The young stalks can be pulled when under ; the inner stems can be eaten raw. The roots can be washed, peeled, cut into small pieces, boiled, and simmered in syrup to make candy.
In herbal medicine
Sweet flag has a long history of use in Chinese, Nepalese, and Indian herbal traditions. Sweet flag was and is used in herbalism by the Chipewyan people.
Horticulture
This plant is sometimes used as a pond plant in horticulture. There is at least one tetraploid ornamental cultivar known; it is usually called 'Variegatus', but the RHS recommends calling it 'Argenteostriatus'.
Insecticide and antifungal
The asarone from A. calamus, found most abundantly in the dried and pulverized roots, has been identified as having insecticidal properties. β-asarone also exhibits anti-fungal activity by inhibiting ergosterol biosynthesis in Aspergillus niger. However, asarone's toxicity and carcinogenicity in mammals (including humans) means that it may be difficult to develop any practical medications or insecticides based on it.
Symbolism
According to some interpretations, American poet Walt Whitman used the plant to represent homoerotic male love because of its phallic connotations.