乌苏早熟禾 wu su zao shu he

Poa ussuriensis f. angustifolia I. C. Chung; P. ussuriensis f. scabra I. C. Chung.

Weakly perennial, loosely tufted. Culms erect, 30–80 cm tall, ca. 0.8 mm in diam., scabrid below nodes, nodes 3 or 4(–5), 2 or 3 exposed. Leaf sheaths very compressed with a winged keel, 4–13 cm, 1/2–1 × as long as blade, uppermost closed for 2/3–3/4 of length; blade flat or weakly folded, thin, deeply keeled, 2–15 cm × (1.5–)2–3(–4.5) mm, adaxially scabrid, margins densely scabrid; ligule (0.5–)1–2(–2.5) mm, abaxially scabrid, apex truncate to obtuse, collars scabrid, margins glabrous. Panicle open, lax, diffuse, 7–20 cm, broad, longest internodes 3–5 cm; branches eventually spreading, lax, 2–5 per node, slender, scabrid on and between angles throughout, longest to 12 cm with 3–13 loosely arranged spikelets in distal 1/3. Spikelets oblong-lanceolate, light green, (3–)4–6 mm, florets 3–5(–6); vivipary absent; rachilla internodes ca. 1 mm, smooth, glabrous; glumes unequal, acute, keels sparsely scabrid, lower glume 1.5–2 mm, 1-veined, upper glume 2.5–3 mm, 3-veined; lemmas 3–4 mm, apex acuminate, keel villous for 2/3 of length, marginal veins for 1/3, intermediate veins prominent, area between veins minutely bumpy, glabrous; callus sparsely webbed; palea smooth or minutely bumpy between keels, keels scabrid. Anthers 0.4–1 mm. Fl. and fr. Jun. 2n = 28, 42.

Deciduous forests, mixed forests, glades, riparian gravels. Heilongjiang, ?Jilin (expected) [Korea, Russia (Far East)].

Poa ussuriensis is common on the Russian side of the Chinese border east and west of Vladivostok. Poa radula Franchet & Savatier was reported in FRPS (9(2): 113–114. 2002) from Jilin, but it is doubtfully present in China. According to Probatova (in Tzvelev, Sosud. Rast. Sovetsk. Dal'nego Vostoka 1: 283. 1985), P. radula is a species of Sakhalin, the Kuril Islands, and S Kamchatka, but is not found elsewhere in the Russian Far East, China, or Japan. Chung (Korean Grass. 72. 1965) reported it from S Korea, but not N Korea or China; Japanese authors have not mentioned it for Korea or China; and Kitagawa (Neo-Lineam. Fl. Manshur. 102–105. 1979) did not list it for Manchuria. Poa radula can be difficult to distinguish from P. ussuriensis: it has a broader leaf blade, (3–)4.5–10 mm wide, longer ligule, (1.5–)2.5–4 mm, larger spikelets (5–)6–8(–10) mm, and hexaploid chromosome number.