Plants annual. Culms 2-35 cm. Sheaths of the flag leaves inflated; auricles not developed; ligules 1.5-3 mm, rounded to acute; blades 1-5 (7) cm long, 1.5-5 mm wide, flat or folded. Panicles 0.5-5.5 cm long, 3-7 mm wide, ovoid to shortly cylindrical, cuneate at the base, widest at or above midlength. Glumes 2.2-4.4 mm, oblong-lanceolate, keels ciliate, tapered, apices parallel or divergent, awns 0.3-1 mm, usually parallel, sometimes divergent; lemmas about 1/3 as long as the glumes, glabrous or pubescent; anthers 0.3-1.2 mm. 2n = 14.
N.Y., N.J., Mass., Oreg.
Phleum arenarium is native to maritime sands and shingles of southern and western Europe. It is known only from old ballast dump records in the Flora region.
"decumbent" is not a number.