Plants summer annuals. Leaves 1.5-4 mm wide, flat or involute. Lateral spikelets: lower glumes usually setaceous, occasionally a little widened, but not winged. 2n = 14, 28.
Hordeum marinum subsp. gussoneanum grows in grassy fields, waste places, and open ground. It was introduced to North America from the Mediterranean area, and it is now an established weed, especially in western North America.
POST PUBLICATION AMENDMENT
Jakob et al. (2007) concluded that the two suspecies of Hordeum marinum should be treated as species. Following their recommendation, Hordeum marinum subsp. gussoneanum should be treated as Hordeum geniculatum All. Note added by Barkworth, 2017.
Much like no. 3 [Hordeum pusillum Nutt.]; lvs narrow, 1-2.5(-4) mm wide; spikelets small, 1.5-4 cm (excl. awns); lateral spikelets on straight or slightly curved pedicels 0.7-1 mm, their florets much reduced, short-awned and borne on rachilla-joints 0.1-0.5 mm; glumes (6-)9-16 mm, all awn-like; fertile lemma glabrous, tapering into a short awn 8-16 mm, surpassing and stouter than the awns of the glumes; anthers 0.6-1 mm; 2n=14, 28. Moderately moist waste places; Mediterranean sp., commonly intr. in w. U.S. and sporadic with us. (H. gussoneanum; H. hystrix)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.