Sweet Flag
Calamus or Common Sweet Flag (Acorus calamus) is a plant from the Acoraceae family, Acorus genues.  It is a tall perennial wetland monocot with scented leaves and rhizomes which have been used medicinally, for its odor, and as a psychotropic drug. It is known by a variety of names, including cinnamon sedge, flagroot, gladdon, myrtle flag, myrtle grass, myrtle sedge, sweet cane, sweet myrtle, sweet root, sweet rush, and sweet sedge. Probably indigenous to India, Acorus calamus is now found across Europe, in southern Russia, northern Asia Minor, southern Siberia, China, Japan, Burma, Sri Lanka, and northern USA.

# Botanical information
The morphological distinction between the Acorus species is made by the number of prominent leaf veins. Acorus calamus has a single prominent midvein and then on both sides slightly raised secondary veins (with a diameter less than half the midvein) and many, fine tertiary veins. This makes it clearly distinct from Acorus americanus.
The leaves are between 0.7 and 1.7 cm wide, with average of 1 cm. The sympodial leaf of Acorus calamus is somewhat shorter than the vegetative leaves. The margin is curly-edged or undulate. The spadix, at the time of expansion, can reach a length between 4.9 and 8.9 cm (longer than A. americanus). The flowers are longer too, between 3 and 4 mm. Acorus calamus is infertile and shows an abortive ovary with a shriveled appearance.

# Chemistry
Both triploid and tetraploid calamus contain asarone, but diploid does not contain any.

# Regulations
Calamus and products derived from calamus (such as its oil) were banned in 1968 as food additives and medicines by the United States Food and Drug Administration.

# Usage
Calamus has been an item of trade in many cultures for thousands of years. Calamus has been used medicinally for a wide variety of ailments.
In antiquity in the Orient and Egypt, the rhizome was thought to be a powerful aphrodisiac. In Europe Acorus calamus was often added to wine, and the root is also one of the possible ingredients of absinthe. Among the northern Native Americans, it is used both medicinally and as a stimulant; in addition, the root is thought to have been used as an entheogen among the northern Native Americans.  In high doses, it is hallucinogenic.

# Cultural symbolism
The calamus has long been a symbol of male love. The name is associated with a Greek myth: Kalamos, a son of the river-god Maeander, who loved Karpos, the son of Zephyrus and Chloris. When Karpos drowned, Kalamos was transformed into a reed, whose rustling in the wind was interpreted as a sigh of lamentation.
The plant was a favorite of Henry David Thoreau (who called it sweet flag), and also of Walt Whitman, who added a section called The Calamus Poems, celebrating the love of men, to the third edition of Leaves of Grass (1860). In the poems the calamus is used as a symbol of love, lust, and affection. It has been suggested that the symbology derives from the visual resemblance of the spadix to the erect human penis.
The name Sweet Flag refers to its sweet scent (it has been used as a strewing herb) and the wavy edges of the leaves which are supposed to resemble a fluttering flag.
In Japan, the plant is a symbol of the samurai's bravery because of its sharp sword-like leaves. Even now many families with young boys enjoy "Sweet Flag Bath (shobu yu)" in the Boy's Festival (Tango no Sekku) on May 5.

# Etymology of the word Calamus
Cognates of the Latin word Calamus are found in both Greek (kalamos, meaning "reed") and Sanskrit (kalama, meaning "reed" and "pen" as well as a sort of rice)  strong evidence that the word is older than all three languages and exists in their parent language, Proto-Indo European. The Arabic word qalam (meaning "pen") is likely to have been borrowed from one of these languages in antiquity, or directly from Indo-European itself.
From the Latin root "calamus", a number of modern English words arise:
- calamari, meaning "squid", via the Latin calamarium, "ink horn" or "pen case", as reeds were then used as writing implements;
- calumet,  another name for the Native American peace pipe, which was often made from a hollow reed;
- shawm, a medieval oboe-like instrument (whose sound is produced by a vibrating reed mouthpiece);
- chalumeau register, the lower notes of a clarinet's range (another reed instrument).