Acorus calamus L.

Rhizome stout, 4-10(-20) cm long, (0.8-)1-1.5(-3) cm diam., aromatic; roots at the lower side of the rhizome. Leaves several, ensiform, mid-green, (60-)70-100(-150) by (0.7-)1-2(-2.5) cm (mostly 1-1.5 cm wide), base green to reddish or red, apex acuminate, midrib conspicuous on both sides. Peduncle compressed-triangular, (15-)40-50 cm long. Spathe leaf-like, mid-green, 30-50 cm long, acute, also with conspicuous midrib. Spadix straight or slightly curved, erect, oblique, narrowly conic to subcylindrical (tapering towards apex), 4.5-8(-10) cm long, 0.6-1.2(-1.5) cm diam., densely flowered. Flowers perigoniate, yellowish green, c. 1.8-2 mm diam. seen from above; tepals oblong, keeled, apex triangular-hooded, membranous, (2-)2.5-3 by 1-1.2(-1.4) mm; filaments oblong, flat, 2-2.5 by 0.3-0.5 mm; anthers 0.4-0.5 mm diam., cream coloured; pollen grains c. 20 μm long, exine shallowly and remotely foveolate; gynoecium obconic-cylindric, 2.5-3.5(-4) mm long, (0.8-)1-2.3 mm diam., with conical, spongy apex and very small stigma; ovary 2-or 3-locular, ovules several, orthotropous, placentation apical. Infructescence 1.5-2 cm diam., straw-brown at maturity, berries densely arranged; berry oblong-obovoid, 1-few-seeded, (3.5-)4-4.5 mm long, c. 2-3(-3.5) mm diam.; seed oblong-ellipsoid to ovoid, 2.5-3(-4) mm long, 1-1.2(-1.8) mm diam., without bristles, testa nearly smooth and covered with very small pits (slightly foveolate), light brown.

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.

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.

It can be grown by dividing the rootstock. It can also be grown by seeds.