Plants annual or perennial; cespitose, occasionally rhizomatous. Culms 14-100 cm, ascending to erect; nodes pubescent to hirsute. Sheaths open; auricles absent; ligules of hairs or membranous and ciliate; blades 1-5 mm wide, flat or involute. Primary inflorescences terminal, open panicles, with few spikelets, exserted or partially included in the upper sheath, apices exceeding the upper leaf blades, axillary panicles sometimes also present; cleistogamous inflorescences also present in the upper sheaths. Spikelets laterally compressed, purplish, with 2-5 florets; sterile florets above the fertile florets; rachillas prolonged; disarticulation above the glumes and beneath the florets and, subsequently, at the cauline nodes. Glumes equal or unequal, shorter than the first lemma, 1-veined, keeled; calluses hairy; lemmas 3-veined, veins villous, apices bilobed to incised, midveins sometimes extending into an awn, awns to 11 mm; paleas bowed-out, keels hairy, distal hairs 0.5-2 mm, longer than those below; lodicules 2, truncate; anthers 3, yellow or reddish-purple; stigmas pink to purple. Caryopses dorsiventrally compressed. x = 10. Name from the Greek triplasios, triple, alluding to the awn and long lobes of the type species, Triplasis americana.
Spikelets 2-6-fld, with long rachilla-joints, disarticulating above the glumes and between the lemmas; glumes chiefly equal, 1-veined, acute, smooth; lemmas oblong, rounded on the back, hairy on the 3 parallel veins, 2-lobed with an awn between the lobes; palea shorter than and soon diverging from the lemma, densely villous on the 2 keels in the upper half; tufted grasses with many short internodes, loose sheaths, a ligule of short hairs, and short panicles at first included in the upper sheath, eventually exsert with spreading branches. 2, N. Amer.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.