66. Poa compressa Linnaeus, Sp. Pl. 1: 69. 1753.
加拿大早熟禾 jia na da zao shu he
Perennials, strongly rhizomatous, shoots extravaginal. Culms wiry, compressed, erect, often geniculate at base, simple or sparsely tufted, 15–50(–60) cm tall, 1.5–2 mm wide, nodes compressed, 3–6, 2–5 exserted. Leaf sheaths compressed to keeled, smooth, uppermost closed for 1/10–1/5 of length; blades flat, 5–12 cm × 1.4–4 mm, surfaces smooth or adaxially scabrid; ligule 1–3 mm, abaxially scabrid, truncate to obtuse. Panicle contracted or slightly open, erect, narrow, 4–11 × 0.5–1(–3) cm; branches erect or steeply ascending, or eventually spreading, 1–3 per node, densely scabrid angled from base, longest 2–4 cm with spikelets moderately crowded from the base or in distal 2/3. Spikelets ovate-lanceolate, 3.5–5 mm, florets 2–4; glumes lanceolate, nearly equal, 2–3 mm, 3-veined, apex acute or thinly mucronate, keel scabrid, rachilla smooth or minutely bumpy; lemmas oblong, 2.3–3.5 mm, apex obtuse, keel shortly villous for 2/3 of length, marginal veins to 1/3, intermediate veins faint, areas between veins glabrous; callus sparsely webbed or glabrous; palea keels scabrid. Anthers 1.3–1.8 mm. Fl. and fr. Jun–Aug. 2n = 14, 35, 42, 45, 49, 50, 56, 59.
Moist grassy places in forests. Hebei, Jiangxi, Qinghai, Shandong, Taiwan, Xinjiang, Yunnan [India (Himachal Pradesh), Japan, Kazakhstan, Russia (Far East, Siberia); Africa, SW Asia, Australia, Europe, North and South America, Pacific Islands].
Poa compressa is native to W Eurasia. It is infrequent in China and is perhaps present only as an introduction in C to E Russia and China. It is distinguishable by its strong rhizome system, long, open sheaths, compressed culms and nodes, and scabrid-angled panicle branches. It is a good soil binder in riparian habitats. It is expected in Heilongjiang because it is frequent on the Russian side of the Chinese border.