Sweet flag, sway or calamus, among many 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, there is no clinical evidence for its safety or efficacy – and ingested calamus may be toxic– leading to its commercial ban in the United States.
Sweet Flag is a perennial herb 1-4 ft tall, consisting of tufts of basal leaves that emerge directly from a spreading rootstock. These basal leaves are erect and sword-shaped, resembling Iris leaves. They are flattened, smooth along the margins, and have parallel veins. There is often an off-center ridge/indentation along the length of each leaf. Sometimes the base of the leaves or their margins are slightly red. The inflorescence is a cylindrical spadix that is about 2–4 inches in length and semi-erect. This spadix is covered with tiny greenish yellow flowers in a diamond- shaped pattern. Each flower has 6 tepals and 6 stamens. The covering spathe, which is found in many plants of the same family, is absent here. The blooming period occurs from late spring to early summer and lasts about a month. Both the crushed foliage and rootstocks have a pleasant aromatic fragrance. The root system consists of shallow branching rhizomes that are stout and knobby. Tufts of basal leaves occur at intervals along these rhizomes, while coarse fibrous roots develop below. This plant multiplies by its rhizomes. Sweet Flag is found in the Himalayas, at altitudes of 100-2300 m and Western Ghats. Flowering: March-May.
A strongly aromatic semi-aquatic perennial herb; rhizomes creeping, jointed, somewhat vertically compressed, 1.3-2.5 cm thick, pale to dark brown and spongy inside. Leaves narrow, up to 80 cm long, linear to narrowly ensiform, glossy bright green, apex acute, base amplexicaul; petioles sheathing for 20-50 cm. Flowers pale green, fragrant, arranged compactly on a sessile, cylindrical, stumpy spadix 5-7 cm long. Fruits (berries) green, angular, 3-celled, fleshy, containing 1-3 oblong seeds.
The rhizome of Sweet Flag is very pungent and bitter in taste. It helps to promote memory, longevity and good voice.