Plants perennial (annual elsewhere), sometimes with rhizomes, forming tufts or less commonly clumps or colonies. Flowering stems erect to ascending or less commonly spreading, glabrous or roughened to short‑hairy. Leaf sheaths rounded on the back or keeled, glabrous or roughened to short‑hairy, the ligule a membrane, this sometimes short and/or uneven to minutely hairy along the margin. Leaf blades flat, folded lengthwise, or with inrolled margins, glabrous or variously roughened or hairy. Inflorescences open to spikelike panicles, terminal or in some species also lateral from the leaf axils, ovate to linear in outline, with spreading or appressed branches. Spikelets with 1 floret (rarely a few spikelets per inflorescence with 2 florets in some species), slightly to moderately flattened laterally, disarticulating above the glumes, the glumes sometimes also shed with age. Glumes about the same length or the lower glume somewhat shorter than the upper glume, the body shorter than to slightly longer than the floret, awnless or awned, 1(–3)‑nerved, rarely nerveless, usually keeled, glabrous or more commonly roughened along the midnerve. Lemma 3‑nerved, the lateral nerves sometimes faint, awnless or awned, rounded on the back, the base glabrous or with a tuft of hairs less than 1/2 as long as the lemma, otherwise glabrous to roughened along the midnerve or short‑hairy. Palea about as long as the lemma, not splitting longitudinally at maturity to expose the fruit. Stamens 3. Fruits linear to narrowly elliptic in outline, reddish brown to dark brown. One hundred twenty‑five to 160 species, nearly worldwide, but mostly in the New World (especially North America).

Many of the species in Missouri belong to a taxonomically difficult complex, most of which is characterized by the production of one to several, prominent, scaly rhizomes, which may reach 10 cm or more in length, and loosely ascending to spreading, strongly 2‑ranked, bluish green to grayish green leaves. This complex was monographed by Pohl (1969), who not only refined the taxonomy, but in doing so altered the limits of some of the species, such that keys in most older floristic manuals no longer work. Observations of the rootstocks of plants are important for proper species determinations in the genus, and collectors should check for the presence of rhizomes when gathering specimens of Muhlenbergia. The 3‑nerved lemmas distinguish Muhlenbergia from all species of Missouri Sporobolus except S. ozarkanus and S. vaginiflorus. In contrast to all Missouri species of Muhlenbergia (which are perennials with at least some of the inflorescences conspicuous and exserted), these two taxa are annuals with the inflorescences all or mostly enclosed within the leaf sheaths at maturity.