Description from Flora of China
Poa annua var. sikkimensis Stapf in J. D. Hooker, Fl. Brit. India 7: 346. 1896 ["1897"]; P. eragrostioides L. Liu; P. tunicata Keng ex C. Ling.
Annuals or short-lived perennials, tufted to weakly stoloniferous. Culms erect or arching, or geniculate ascending, 4–42 cm tall, 0.5–2 mm in diam., smooth, nodes 1–3(–4), none or 1 exserted, uppermost to 1/3 way up culm. Leaf sheaths loose, smooth, glabrous, 2–8 cm, 1–3 × as long as blade, uppermost closed for 1/3–1/2 of length; blade flat, thin, 3–10 cm × (1.5–) 2–5 mm, surfaces smooth or sparsely scabrid, margins scabrid, apex acutely prow-tipped, of tillers 1–10 cm; ligule 1.5–4(–6) mm, abaxially smooth or sparsely scabrid, apex obtuse to acute, collars glabrous. Panicle loosely contracted to open, oblong to pyramidal, 3–15(–19.5) × 1.5–5 cm, longest internodes 0.5–3 cm; branches obliquely ascending, spreading, or reflexed, flexuous, 2 per node, proximally smooth, distally scabrid, longest to 1–7 cm with 4–30 spikelets in distal 2/3. Spikelets ovate, usually purple tinged, 3.8–5(–6) mm, florets 3–5; vivipary absent; rachilla internodes 0.4–0.9 mm, smooth, glabrous; glumes usually purple, subequal to unequal, broad, keels smooth or sparsely scabrid, lower glume 1.5–2.7 mm, 1-veined, upper glume 2–3.1 mm, 3-veined; lemmas broadly elliptic, 2.5–3.3 mm, apex obtuse to acute, keel pilulose to shortly villous, rarely glabrous, for 1/2 length, marginal veins to 1/3, intermediate veins prominent, areas between veins smooth, glabrous; callus glabrous; palea glabrous between keels, keels sparsely scabrid, some smooth, medially sparsely pilulose. Anthers 0.5–0.9 mm. Fl. and fr. Jul–Sep. 2n = 28, 42.
Poa sikkimensis lacks a webbed callus and has ligules 2–6 mm. It is most difficult to distinguish from P. annua, but has sparsely scabrid palea keels and branches and no pubescence on the intermediate veins of the lemmas.
Grassy slopes, meadows, marshy ground, sandy bottoms, roadsides, disturbed ground; 3000–4700 m. SW Gansu, S Qinghai, W Sichuan, E Xizang (Yadong, Zayü), NW Yunnan [Bhutan, India (Assam, Sikkim), Nepal].