Acorus calamus is a perennial herb with special fragrance. Rhizomes are thick, with a diameter of 10- 15mm, lateral branches, multiple connections at nodes and fibrous roots. Leaves are born at the base, simple leaves, arranged in 2 rows, stipe at the base, sword-shaped, leathery, 50-80cm long, sometimes up to 150cm, 0.8- 1.5cm wide, with sharp apex and prominent midvein. Flowering from May to July, the inflorescence is cylindrical, 3-8cm long and 7- 15cm wide, with leaflike bracts 1, small flowers, dense yellow-green, and 6 perianth segments. 6 stamens. Ovary 2-4-loculed. Berries are obovate and red when they are ripe.
The rhizome of Acorus calamus is flat and cylindrical, with few branches, length 10-20cm, diameter 1- 1.5cm ... The surface is white to reddish brown with fine longitudinal stripes. Internodes are 0.2- 1.5cm long, and there is a concave root mark on the upper side. Hard texture, spongy fracture, white or light brown, obvious endodermis ring, many small cavities and vascular bundles. Strong and single-minded. Bitter and spicy.