Plants annual or perennial; with or without rhizomes. Culms 10-460 cm, prostrate, decumbent or erect, distal portions sometimes floating, sometimes rooting at the lower nodes; nodes usually glabrous; internodes hollow or solid. Sheaths open, compressed; auricles absent; ligules usually absent but, if present, of hairs; blades linear to linear-lanceolate, usually more than 10 times longer than wide, flat, with a prominent midrib. Inflorescences terminal, panicles of simple or compound spikelike branches attached to elongate rachises, axes not terminating in a bristle, spikelets subsessile, densely packed on the angular branches; disarticulation below the glumes (cultivated taxa not or tardily disarticulating). Spikelets plano-convex, with 2(3) florets; lower florets sterile or staminate; upper florets bisexual, dorsally compressed. Glumes membranous; lower glumes usually 1/4-2/5 as long as the spikelets (varying to more than 1/2 as long), unawned to minutely awn-tipped; upper glumes unawned or shortly awned; lower lemmas similar to the upper glumes in length and texture, unawned or awned, awns to 60 mm; lower paleas vestigial to well-developed; upper lemmas coriaceous, dorsally rounded, mostly smooth, apices short or elongate, firm or membranous, unawned; upper paleas free from the lemmas at the apices; lodicules absent or minute; anthers 3. Caryopses ellipsoid, broadly ovoid or spheroid; embryos usually 0.7-0.9 times as long as the caryopses. x = 9. Name from the Greek echinos, hedgehog, and chloa, grass, in reference to the bristly or often awned spikelets.