Plants perennial; rhizomatous, sometimes producing aquatic leaves when submerged. Culms (5) 10-100 cm, erect, glabrous, rooting at the lower nodes; nodes glabrous. Sheaths of aquatic leaves closed to near the apices, translucent, pale pinkish brown; collars inconspicuous; ligules acute; blades pinkish brown. Sheaths of aerial leaves usually closed for over 1/2 their length, sometimes open to the base, opaque, green to olive-green, glabrous; collars conspicuous as a zone of contrasting color; auricles absent; ligules membranous, truncate, lacerate; blades usually flat, glabrous, upper blades conspicuously longer than the lower blades. Inflorescences open panicles; branches stiff and ascending to pendulous, glabrous, some branches longer than 1 cm. Spikelets pedicellate, somewhat laterally compressed, with (1) 2-7 (9) florets; rachillas prolonged beyond the base of the distal floret, glabrous; disarticulation above the glumes, beneath the florets. Glumes subequal, broadly lanceolate to ovate, membranous to subcoriaceous, glabrous, 1-3 (5) -veined, acute to obtuse, unawned; calluses short, blunt, shortly pubescent to almost glabrous; lemmas ovate, glabrous, membranous to subcoriaceous, with 3 (5) obscure veins, lateral-veins usually not reaching the lemma apices, apices entire or somewhat erose, obtuse, unawned or rarely the central vein extended as a short mucro to about 0.2 mm; paleas subequal to the lemmas; lodicules 2, free, glabrous, toothed or entire; anthers 3; ovaries glabrous. Caryopses shorter than the lemmas, concealed at maturity, falling free; hila broadly ovate, 1/6 – 1/5 the length of the caryopses. x = 7.
B.C., Greenland, Nfld. and Labr. (Nfld.), Man., N.W.T., Nunavut, Ont., Que., Yukon, Alaska
Arctophila is a monospecific, but highly polymorphic, holarctic genus closely related to Dupontia (p. 602).
"decumbent" is not a number.