43. Diarrhena P. Beauv.

(Brandenburg et al., 1991b)

Plants with C₃ photosynthesis, perennial, with stout rhizomes, forming loose colonies or clumps. Aerial stems 50–120 cm long, annual, not woody, unbranched. Leaf sheaths open most of their length, the ligule membranous, minutely hairy along the margin. Leaf blades 20–40 cm long, 10–18 mm wide, flat, the midvein usually off‑center, sometimes with a pair of short auricles at the base, the surfaces (or sometimes only the upper surface) roughened, dark green, shiny. Inflorescences slender panicles with ascending branches, with mostly numerous spikelets. Spikelets oblong to elliptic or ovate, circular in cross‑section when young, somewhat flattened laterally at maturity, with 2–5(–7) perfect florets, the axis extended past the uppermost fertile floret and with a terminal, reduced, sterile floret, the remaining florets perfect, disarticulating above the glumes and between the florets. Glumes rounded to bluntly angled on the back, glabrous or roughened. Lower glume triangular, 1(3)‑nerved. Upper glume oblong‑elliptic, 3‑ or 5‑nerved. Lemmas pointed or with a short, stout awn at the tip, rounded to bluntly angled on the back, 3‑nerved, glabrous or roughened. Paleas shorter than the lemmas, strongly 2‑nerved, blunt and usually notched at the tip. Stamens 2, the anthers yellow. Fruits beaked at the tip, circular in cross‑section, straw‑colored to dark brown at maturity. Four or 5 species, eastern U.S. west to South Dakota and Texas; Asia.

Many authors have treated Diarrhena as an exclusively North American genus of only one species with two varieties. If segregated, the Asian taxa are called Neomolinia Honda. Recent studies by Brandenburg et al. (1991b) have tended to reinforce the distinctness of the two North American taxa, and although very closely related, they are treated as separate species below.

Plants of Diarrhena are slow‑growing, woodland perennials, whose dark green, shiny foliage and graceful inflorescences have only recently been appreciated for their horticultural value as shade‑tolerant ornamentals.