Herbs annual or perennial, mostly cespitose; rhizomes present or absent, if present without cormose buds. Culms tufted or widely spaced, erect to leaning, culm tips hispid-hirsute, internodes glabrous proximal to inflorescence. Leaves: sheaths at culm base or apex sometimes hairy, sheaths at or toward midculm usually glabrous; principal blades linear or lance-linear, flat, 5-20 cm, hispid-ciliate, abaxially hispid, pilose, or glabrous, adaxially glabrous to pilose. Inflorescences of spikelets in clusters 1-3(-5). Spikelets ovoid, lance-ovoid, or cylindric, 8-15(-20) mm, apex acute; fertile scales obovate or oblong, 2-3.5 mm; cusp spreading-excurved, 2/3 or more length of scale; evident ribs 5-7, central 3 convergent to cusp. Flowers: florets 2-3 mm; perianth bristles reaching base of perianth blades or beyond, retrorsely barbellate (sometimes with narrow blades); perianth blades with long claw, ovate, rounded or retuse, rarely acute, apically or subapically bristled, bristle erect or incurved, short to elongate, retrorsely scabridulous; anthers 1-3, 0.5-1.2 mm. Achenes: stipe and beak nearly as long as fruit; body angles pale, faces deep glossy brown, red-brown, or yellow, 1 mm; beak tip narrow, usually papillose.
Rhizomatous perennial 2-5(-10) dm; mid-stem sheaths usually smooth, the others hispid or hirsute; larger blades 5-20 cm נ3-7 mm, hispid-ciliate and often also hairy on the surfaces; spikelets 8-15(-20) mm, in 1-3(-5) clusters; scales 2.5-3.5 mm, 3 of the 5-7 strong raised nerves convergent and exserted to form a spreading awn usually at least 2/3 the length of the scale; bristles retrorsely barbellate, reaching or often surpassing the base of the pet-blades, these ovate, blunt or retuse, with the midrib excurrent as a retrorsely barbellate dorsal-subapical bristle; anthers 3, 0.9-1.2 mm; 2n=(30), 46. Wet sunny places; C. Amer. and W.I., n. to Ill., Mo., and Nebr. Most of our plants are var. simplex, as described above. The var. aristulata (Torr.) Kral, mostly on the s. Great Plains and entering our range in w. Mo., lacks rhizomes and is usually annual, seldom over 3 dm, with 1-3 anthers 0.5-0.6 mm.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.