Leaves several, ensiform, dark to mid-green, (15-)20-45(-55) by (0.3-)0.5-1(-1.4) cm, apex acuminate, midrib lacking. Flowers perigoniate, yellowish, yellow-green to somewhat whitish, 1.8-2 mm diam. seen from above, tepals more or less oblong, keeled, rounded at apex or acute, membranous, 1.5-2 by 0.7-1 mm;
Asia-Temperate: Korea present; Taiwan (Taiwan present), Asia-Tropical: Cambodia (Cambodia present); Laos (Laos present); Philippines (Philippines present); Vietnam (Vietnam present), Japan present, Luzon present, Province Laguna present, Russia present, San Antonio present, from northeast India to Myanmar, Thailand and Indo-China present
Throughout China, Taiwan, East Siberia (Russia) and from northeast India to Myanmar, Thailand and Indo-China (Vietnam, Laos, Cambodia), Korea, Japan; in Malesia: Philippines (Luzon, Province Laguna, San Antonio).
Acorus gramineus is a variable species; there is a continuous series of measurements which overlap between different forms. Plants with shorter spadices were described with a leaf width of 7-13 mm and it is even said that the leaves are smaller than 6 mm wide; some collections have quite long spadices. However, there are many collections with spadices of intermediate length. The flowers of these different types can hardly be distinguished. The size of the plants also depends on growing conditions, especially on the available nutrients. If infraspecific taxa are to be distinguished, perhaps as varieties, then it must be emphasized that intermediates always exist. In the horticultural literature several cultivars are recognized, which is a good way to distinguish different forms. There are also variegated cultivars and these are often preferred in gardens. The dwarf form, described as A. pusillus or A. gramineus var. pusillus, is considered as a cultivar, ‘Pusillus’, today and which is known only from cultivation.