Plants annual or perennial; usually rhizomatous, often cespitose, sometimes mat-forming, rarely stoloniferous. Culms 2-300 cm, erect, geniculate, or decumbent, usually herbaceous, sometimes becoming woody. Sheaths open; ligules membranous or hyaline (rarely firm or coriaceous), acuminate to truncate, sometimes minutely ciliolate, sometimes with lateral lobes longer than the central portion; blades narrow, flat, folded, or involute, sometimes arcuate. Inflorescences terminal, sometimes also axillary, open to contracted or spikelike panicles; disarticulation usually above the glumes, occasionally below the pedicels. Spikelets with 1(2-3) florets. Glumes usually (0)1(2-3)-veined, apices entire, erose, or toothed, truncate to acuminate, sometimes mucronate or awned; lower glumes sometimes rudimentary or absent, occasionally bifid; upper glumes shorter than to longer than the florets; calluses poorly developed, glabrous or with hairs; lemmas glabrous, scabrous, or with short hairs, 3-veined (occasionally appearing 5-veined), apices awned, mucronate, or unawned; awns, if present, straight, flexuous, sinuous, or curled, sometimes borne between 2 minute teeth; paleas shorter than or equal to the lemmas, 2-veined; anthers (1-2)3, purple, orange, yellow, or olivaceous. Caryopses elongate, fusiform or elliptic, slightly dorsally compressed. Cleistogamous panicles sometimes present in the axils of the lower cauline leaves, enclosed by a tightly rolled, somewhat indurate sheath. x = 10. Named for Gotthilf Henry Ernest Muhlenberg (1753-1815), a Lutheran minister and pioneer botanist of Pennsylvania.