Plants perennial, up to 50 cm tall, in loose to dense tufts. Culms usually erect; nodes glabrous. Leaves: auricles not present; blades usually flat, usually scabrous, occasionally pubescent. Spikes 3.5-7 cm long, pale to yellowish green with a purplish tinge; Central spikelets sessile; glumes 5-9 mm long, lower portion 0.3-0.6 mm wide, narrowly ovate, flattened; lemmas mostly glabrous but scabrid near the tip; awns 2-5 mm long; anthers 1-2.5 mm long, usually yellow, sometimes purplish. Lateral spikelets usually sterile; lower glumes flattened, usually abruptly flattened with a distinct shoulder or teeth below the awn; upper glumes setaceous; lemmas obtuse to acute.
Hordeum flexuosum grows in pastures, riverbeds, alongside ditches and in somewhat saline places near lakes, at low elevations. It thrives in habitats where there is some distrubance.
Hordeum flexuosum has iis center of distribution in the province of Buenos Aires, Argentina, with scattered localities elsewhere. Older collections supposedly collected in Columbia are puzzling because they are outside the main distribution area; there are no recent collections but Hordeum flexuosum is one of three species recently identified in wool waste from New England in North America.