1. Andropogon L. (beard grass)

Plants perennial, forming clumps. Flowering stems erect, sometimes highly branched above the basal portion, with a longitudinal groove. Leaf sheaths usually somewhat glaucous. Leaf blades linear, not rounded or heart‑shaped at the base, flat or sometimes folded at maturity. Inflorescences sometimes partly enclosed by the subtending leaf sheaths, consisting of 2 or more spikelike racemes, these grouped into palmate (or nearly so) clusters, sometimes appearing to be arranged into narrow, leafy panicles with loosely spaced clusters of spikelets. Individual racemes with the axis and spikelet stalks hairy, breaking apart into joints (as a unit with the associated spikelets) at maturity, the spikelets paired at the nodes. Stalked spikelet staminate or sterile, when sterile usually highly reduced, the stalk not grooved. Sessile spikelet with the perfect, upper floret subtended by a sterile floret, this reduced to a membranous lemma lacking an awn. Glumes of sessile spikelet about equal in length, somewhat longer than the florets, the lower glume strongly 2‑nerved, the upper glume strongly 1‑nerved. Fertile lemma membranous, with the tip split into 2 long, slender teeth, with a long awn attached between the teeth. Palea reduced or absent. Fruits 2–3 mm long, narrowly elliptic in outline, yellow or purplish brown. About 100 species, nearly worldwide, but most diverse in tropical and warm‑temperate regions.

The traditional Andropogon as treated by Steyermark (1963) has been split into several genera by more recent authors (Gould, 1967, 1975; Clayton and Renvoize, 1986). In addition to Andropogon in the strict sense, the segregate genera Bothriochloa and Schizachyrium occur in Missouri (see treatments below).