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. Flowers perigoniate, yellowish green, c. 1.8-2 mm diam. seen from above;
Asia-Tropical: Borneo present (Sabah present, Sarawak present); Jawa (Jawa present); Malaya (Singapore present); New Guinea present; Philippines (Philippines present); Sulawesi (Sulawesi present); Sumatera (Sumatera present), Flores present, Greece and the Mediterranean absent, Lesser Sunda Is present, Lombok present, North America present, North Asia extending to subtropical as well as tropical Asia present, North Temperate Europe present, Timor present, eastward to the Himalayas present
North Temperate Europe (except Greece and the Mediterranean), North Asia extending to subtropical as well as tropical Asia, eastward to the Himalayas, North America; in Malesia: Sumatra, Singapore (one coll.), Borneo (one coll. from Sandakan District, Sabah and two from Sarawak), Java, Philippines, Celebes, Lesser Sunda Is. (Lombok, Flores, Timor), New Guinea.
Acorus calamus with its three cytotypes, diploid, triploid and tetraploid, in different geographical regions shows great morphological variability and also a wide variation in the chemical composition of the ethereal oils in the rhizome and leaves. The different cytotypes have been considered as separate species or varieties: var. calamus (or var. vulgaris) for the triploids (2n = 36), var. americanus for the diploids (2n = 22, 24) and var. angustifolius (2n = 44, 48), the latter well documented from Asia. However, A. calamus is considered in this treatment as a variable species and infraspecific taxa are not recognized, because there is overlap in the width of the leaves from 0.8-1.5(-2) cm in Asian collections of different geographical regions, and the length of the spadix is also variable. It is true that most of the Asian plants look somewhat weaker and have narrower leaves, e.g. plants from Borneo (Sarawak) with c. 1 cm wide leaves, but there are also broader ones from Asia and a continuous series of forms exists. Sometimes the leaf margins are more or less undulate. The berries are straw-brown at maturity and never reddish as also reported in literature. The two cytotypes, European and North American (wild plants from Quebec, Canada), are not distinguishable when grown under the same conditions in cultivation, therefore Acorus americanus (Raf.) Raf. or Acorus calamus L. var. americanus Raf. is not accepted as a different taxon. Hand-pollinated inflorescences of the diploid plants set 100 % fruits and seeds, but the flowers are not visited by any insects and without artificial pollination no fruits are produced. Asian tetraploid plants also set fruits in nature, but still no pollinator is known.