Annual Meadow Grass

Poa annua is easily distinguished from other short-anthered Poa, other than P. infirma, by the annual habit, absence of a web on the callus, and the near absence of hooks on the panicle branches and spikelet bracts, in combination with densely pubescent palea keels that lack hooked prickle hairs at the apex. Plants with glabrous florets are sporadically encountered.

Plants perennating by short stolons rooting at the nodes appear to develop repeatedly but sporadically at various elevations with prolonged, cool, mesic growing conditions, possibly in response to trampling. These are sometimes placed in var. reptans. Such plants have been recorded from Yunnan.

Annual Meadow-grass is a very common weedy species found in a variety of habitats. 1400-4300m.

Annuals, sometimes over wintering, infrequently stoloniferous. Culms loosely tufted, erect or oblique, often decumbent, often geniculate, soft, 6–30(–45) cm tall, smooth, nodes 1 or 2(or 3), 1(or 2) exserted. Leaf sheath slightly compressed, thin, smooth, uppermost closed for ca. 1/3 of length; blade light to dark green, flat or folded, thin, 2–12 cm × (0.8–)1–3.5 mm, margins slightly scabrid, apex acutely prow-tipped; ligules 0.6–3 mm, abaxially smooth, glabrous, apex obtuse, margin irregularly dentate, smooth. Panicle open, moderately congested, broadly ovoid to pyramidal, (1–)3–10 cm, as long as wide; branches ascending, spreading, or a few reflexed, 1 or 2(–3) per node, smooth, longest with usually 3–5 spikelets in distal 1/2. Spikelets ovate to oblong, dark to light green, (3–)4–5.5 mm, florets 3–5, distal fertile florets often female; vivipary absent; rachilla internodes 0.5–1.5 mm, smooth, glabrous, hidden or exposed; glumes unequal, smooth or rarely keeled with hooks, lower glume lanceolate and acute to subflabellate and obtuse, 1.5–2(–3) mm, 1-veined, upper glume elliptic, 2–3(–4) mm, 3-veined, the margin angled; lemmas ovate, 2.2–3.5 mm, apex and margins broadly membranous, intermediate veins prominent, keel and marginal, and usually intermediate, veins villous in the lower 1/2, rarely glabrous throughout; callus glabrous; palea keels smooth, densely pilulose to short villous. Anthers 0.6–1 mm, usually at least 2 × as long as wide, or vestigial. Fl. Apr–May, fr. Apr–Jul. 2n = 28.

Tufted annual or short-lived perennial; culms 5-30cm high, erect, spreading or prostrate, sometimes with a creeping base rooting from the nodes, slightly compressed. Leaf-blades flat or folded, 1-14cm long, 1–2(–5)mm wide, flaccid, abruptly tapered to a pointed or bluntly hooded tip, often transversely wrinkled, scaberulous on the margins; ligule blunt, 2–5mm long. Panicle ovate or pyramidal, (1–)3–8(–12)cm long, loose or rather dense; branches paired, spreading or de-flexed after anthesis, smooth. Spikelets with 3–5(-10) closely spaced florets, ovate or oblong, 3–10mm long, pale or bright green, reddish or purplish; glume unequal, the lower lanceolate to ovate, 1.5–3mm long, 1–nerved, the upper elliptic or oblong, 2–4mm long, 3–nerved; lemmas semi-elliptic or oblong in side-view, 2.5–4mm long, blunt, glabrous or sparsely to densely ciliate on the keel and nerves, without any wool at the base; palea nearly as long as the lemma, ciliate all along the keels; anthers 0.6–0.8(–1)mm long.

Cosmopolitan.

Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Nei Mongol, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan, Zhejiang [Afghanistan, Bhutan, India, Indonesia, Japan, Kazakhstan, Korea, Kyrgyzstan, Malaysia, Mongolia, Myanmar, Nepal, New Guinea, Pakistan, Russia, Sri Lanka, Tajikistan, Turkmenistan, Uzbekistan, Vietnam; Africa, SW Asia, Australia, Europe, North and South America, Pacific Islands].

Distribution: Pakistan (Baluchistan, Punjab, N.W.F.P. & Kashmir); cosmopolitan, but avoiding deserts and hot climates.

2300-3500 m

Fl. & Fr. Per.: throughout most of the year, especially March-September.

Weed of disturbed, often moist and shady ground; near sea level to 4800 m.

Poa annua f. reptans (Haussknecht) T. Koyama; P. annua var. reptans Haussknecht; P. crassinervis Honda.