10. Poa supina Schrader, Fl. Germ. 1: 289. 1806.
仰卧早熟禾 yang wo zao shu he
Poa variegata A. Haller, Cat. Pl. Helv. 38. 1800, not Lamarck (1791); P. annua Linnaeus var. supina (Schrader) Link; P. supina subsp. ustulata (S. E. Fröhner) A. Löve & D. Löve; P. ustulata S. E. Fröhner.
Perennials, sometimes stoloniferous; shoots mostly extravaginal. Culms tufted or isolated, oblique, decumbent at base, frequently geniculate above, soft, (4–)8–20(–30) cm tall, 0.5–0.7 mm in diam., smooth, nodes 1 or 2(–3), 1(or 2) exserted. Leaf sheaths thin, smooth, basal ones drying pale brown and soon withering, enclosing culm bases, uppermost closed for 1/4–1/3 of length, 1.5–5 × longer than blade; blade light green, flat or folded, thin, 2–6 cm × 2–3 mm, surfaces smooth, margins smooth or sparsely scabrid, apex acutely prow-tipped; ligule 0.6–1.5 mm, abaxially smooth, glabrous, apex obtuse. Panicle open to loosely contracted, compactly pyramidal to ovoid, diffuse to moderately congested, (1.5–)2–5 cm, 1–2 × as long as wide; branches ascending to spreading, 1 or 2 per node, rounded, smooth, longest to 2 cm with 2–8 spikelets in distal 1/2. Spikelets ovate to oblong, light green, frequently purple tinged, 3.5–5(–6) mm, florets 3–6, distal fertile florets often female; vivipary absent; rachilla internodes 0.5–0.8 mm, smooth, glabrous; glumes unequal, smooth or sparsely scabrid, membranous-papery, lower glume lanceolate and acute to subflabellate and obtuse, ca. 1.5 mm, 1-veined, upper glume elliptic, 2–2.5 mm, margin angled, 3-veined; lemmas elliptic or oblong to ovate, membranous-papery, 1.4–3.5(–4) mm, keel and marginal veins sparsely villous or glabrous, smooth, intermediate veins distinct, margins smooth, apex obtuse; callus glabrous; palea keels smooth, hooks absent, shortly villous for most of length. Anthers (1.2–)1.5–1.8(–2.5) mm, or vestigial. Fl. and fr. Jun–Aug. 2n = 14, 28.
Alpine and subalpine meadows on slopes, moist places; 1000–3100 m. Sichuan, Xinjiang, Xizang, Yunnan [Afghanistan, Kashmir, Mongolia, Nepal, Pakistan, Russia (Far East, Siberia), Tajikistan; SW Asia, Europe, North America].
Poa supina has been divided into two taxa since the plants from C Asia, the Himalayas, and Xizang, including some but not all of the material from China, are more densely tufted and less stoloniferous than material from elsewhere. In addition, the branches are reduced to 1 per node, often rebranched near the base, and the palea looks minutely bumpy because of the globose, short cells between the veins. This material could be distinguished as P. supina subsp. ustulata. However, aside from the habit, the differences cited do not seem constant in the material from China, and material from NW China matches P. supina s.s.