Tufted, erect perennial 2-8 dm; lvs 1-3 mm wide, often involute; ligules 1-3 mm; infl 5-25 cm, narrowly contracted to broadly ovoid, the scabrous branches erect or ascending to less often spreading or descending at maturity, the lowest bearing spikelets chiefly above the middle; pedicels very scabrous; spikelets slender, 4-8 mm, 3-9-fld; glumes narrowly ovate, the first 1-2.4 mm, the second 1.6-2.9 mm; lemmas broadly oblong, obscurely veined, minutely hairy at base, scabrous on the margins toward the acute to narrowly (seldom broadly) obtuse tip; first lemma 2.1-3.5 mm; anthers 0.7-1.2 mm; 2n=28, 42, 56. Alkaline places; Wis. to B.C., s. to Kans., N.M., and Calif., and occasionally intr. e. to Me. and N.Y. (P. airoides)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.