Plants annual, (5-)20-40 cm tall, in loose tufts. Culms usually erect; nodes glabrous. Leaves: auricles not present; blades usually flat, more or less pubescent. Spikes 2-7 cm long, pale to yellowish green. Central spikelets sessile; glumes 7-16 mm long, lanceolate, lower portion flattened, up to 1 mm wide; lemmas glabrous or more or less pubescent; awns 5-11 mm long; anthers 0.3-1.3 mm long, yellow. Lateral spikelets: usually sterille; lower glumes with lower portion flattened; upper glumes setaceous.
Hordeum euclastion is native to Central Argentina, Uruguay, and southern Brazil. It is an inbreeding species that shows a wide range of variation in most characters. It differs from Hordeum flexuosum in being annual.