Plants perennial, submerged in fresh water. Rhizome present, terete to slightly flattened. Stems creeping at base, terete to slightly flattened and angular, sparsely branched; stiff axillary turions 1-3 cm × 8-15 mm, each a cluster of hard scales formed by strongly shortened, thickened and broadened leaves. Stipules axillary, convolute to shortly connate, 5-10 mm, membranous and evanescent; leaves sessile, broadly linear to narrowly oblong, 3-8 cm × 3-10 mm, 3-7-veined, margin mostly undulate or crispate, serrate, apex obtuse or rounded. Spikes cylindric, with 2-4 whorls of shortly distant opposite flowers; peduncles 14-65(-125) cm. Carpels 4, shortly connate at base. Fruit ovoid, 3.5-4 mm, abaxial keel distinct, few toothed on lower ridge; beak subequal to or longer than body of carpel, slender. Fl. and fr. Apr-Jul. 2n = 52.

Lakes, streams, ponds, paddy fields. Fujian, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Jiangsu, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan, Zhejiang [Afghanistan, Bangladesh, Bhutan, India, Indonesia (Sumatra), Japan, Kazakhstan, Korea, Kyrgyzstan, Laos, Mongolia, Myanmar, Nepal, Pakistan, Russia, Tajikistan, Thailand, Turkmenistan, Uzbekistan, Vietnam; Africa, SW Asia, Australia, Europe; introduced in North and South America and Pacific islands (New Zealand)].