47. Poa acroleuca Steudel, Syn. Pl. Glumac. 1: 256. 1854.
白顶早熟禾 bai ding zao shu he
Annuals or short-lived perennials. Culms ascending to erect, sometimes slightly swollen at the base, sometimes with moniliform swelling, 30–85 cm tall, 0.6–1 mm in diam., smooth, glabrous to retrorsely strigulose, nodes 3 or 4, 2 exserted. Leaf sheaths weakly keeled, smooth or sparsely scabrid, glabrous or retrorsely strigulose, 8–13 cm, slightly shorter or longer than blade, uppermost closed for over 2/3 of length, lowermost becoming fibrous in age; blades flat, thin, 7–20 cm × (1–)1.5–5(–11) mm, surfaces smooth to moderately scabrid, margins moderately to densely scabrid; ligule 0.5–1.5(–2) mm, abaxially pilulose, apex truncate to rounded, collar margins ciliate. Panicle open, elliptic, narrowly ovate, or pyramidal, exserted, 10–21 × 3–10 cm, longest internodes 3–5.5 cm; branches ascending to widely spreading, or reflexed, 2–5 per node, slender, angular, scabrid from base, longest 3–11 cm with 9–40 spikelets in distal 1/2. Spikelets ovate, green, 2.5–5 mm, florets (2–)3–5; vivipary absent; rachilla internodes 0.5–0.8 mm, smooth to sparsely scabrid, glabrous or pilulose; glumes slightly unequal, lanceolate, keel and veins distally scabrid, lower glume 1.5–2.4 mm, 1-veined, upper glume 2–2.8 mm, 3-veined, often as long or slightly longer than lowest lemma; lemmas oblong, 1.6–2.6(–3) mm, apex obtuse to acute, keel shortly villous for 5/6 of length, marginal veins to 3/4, intermediate veins moderately prominent, area between veins pilulose for 4/5 of length, rarely glabrous; callus sparsely webbed; palea pilulose between keels, keels smooth, rarely with a few apical hooks, pilulose to shortly villous to apex. Anthers (0.4–)0.5–1 (–1.3) mm. Fl. and fr. Apr–Jun. 2n = 28.
Moist and shady grassy places, ditch banks, parks, disturbed ground; 500–1500(–2400) m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shandong, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [Korea, Japan].
Poa acroleuca is usually well marked by the pilulose lemma surfaces and palea keels, callus web presence, and scabrid branches. It appears to intergrade with P. nepalensis, but that species normally has glabrous lemma surfaces, shorter, more contracted panicles, upper glume shorter than the first lemma, smooth, glabrous ligules (at least on the upper culm leaves), and tends to be paler overall.