Plants annual; tufted. Culms 12-45 cm, erect or decumbent. Ligules 1.5-5.5 mm, obtuse; blades 4-12 cm long, 1.2-4 mm wide; upper sheaths conspicuously inflated. Panicles 1.5-6.5 cm long, 5.5-13 mm wide, often dense. Glumes 3-5 mm, connate at the base, not dilated, membranous, pubescent, keels not winged, veins ciliate, apices obtuse; lemmas 3-5 mm, connate in the lower 1/3-1/2, glabrous, apices obtuse, awns 6-10 mm, geniculate, exceeding the lemmas by 3-6 mm; anthers 0.7-1.8 mm, yellow to rusty brown. Caryopses 1.5-2 mm. 2n = unknown.
Calif., Idaho, Wash., Oreg.
Alopecurus saccatus is a native annual that inhabits moist, open meadows, valley plains, and vernal pools, at elevations below 700 m, from Washington to California. Segregates have been treated as species in the past, but the variation between them appears to be continuous, and no habitat differentiation is evident.