5. Erianthus Michx. (plume grass)

(Webster and Shaw, 1995)

Plants perennial, with short, stout, knotty rhizomes, forming clumps. Flowering stems erect, unbranched. Basal leaves few, forming low, sparse rosettes. Leaf sheaths with the ligule membranous, hairy (fringed) along the margin. Leaf blades linear, not rounded or heart‑shaped at the base, flat, the midvein thickened. Inflorescences sometimes partly enclosed by the subtending leaf sheaths, consisting of dense panicles with numerous branches consisting of spikelike racemes (the lowermost branches sometimes branched again), the branched portion of the inflorescence narrowly oblong‑elliptic in outline, the central axis much longer than the branches. Individual racemes with the axis and spikelet stalks with long, silky hairs, breaking apart into joints (as a unit with the associated spikelets) at maturity, the spikelets paired at the nodes. Stalked and sessile spikelets similar in size and appearance, both perfect, the stalk shorter than the sessile spikelet, round in cross‑section, somewhat thickened toward the tip. Spikelets with the perfect, upper floret subtended by a sterile floret, this reduced to a membranous lemma lacking an awn. Glumes somewhat longer than the florets, similar in size and appearance, elliptic‑ovate, pointed at the tip, the lower glume sometimes minutely notched, rounded on the back, faintly 3‑ or 5‑nerved. Lemmas membranous, lanceolate, 1‑ or 3‑nerved, those of the fertile floret awned (except rarely in E. ravennae). Palea of fertile floret much shorter than the lemma. Fruits 2–4 mm long, narrowly elliptic in outline, reddish brown. Twenty‑five to 27 species, North America to South America, Europe, Asia, Africa, Madagascar, Pacific Islands.

Several authors have advocated uniting Erianthus with Saccharum L. under the latter name (Clayton and Renvoize, 1986; Webster and Shaw, 1995). The two genera are said to differ in whether the fertile lemmas generally are awned or not, but there may be reason to believe that this separation is artificial (some awned species may be more closely related to awnless species than to other awned ones). The generic taxonomy requires further study to delineate natural groups within the complex (and how to separate them), and the Missouri species tentatively are retained in Erianthus.