Weak Bluegrass

Nile region, Mediterranean region and Eastern desert.

Mediterranean region, southern Europe, eastwards to the Himalaya and Central Asia; introduced to South America whence it was first described.

Poa infirma differs from P. annua in its shorter, more spherical or slightly lozenge-shaped anthers, and diploid chromosome number. It also has more ascending branches with more crowded spikelets.

Early Meadow–grass is an uncommon weedy species of gardens and farm-land, of no consequence as a fodder grass.

Annuals. Culms loosely tufted, erect or oblique, often decumbent, often geniculate, soft, 5–25 cm tall, smooth, nodes 1 or 2(–3), 1(or 2) exserted. Leaf sheaths, thin, smooth, uppermost closed for ca. 1/3 of length; blade light green, flat or folded, thin, 2–8 cm × 1–3 mm, margins smooth or sparsely scabrid, apex acutely prow-tipped; ligule membranous, 1–3 mm, abaxially smooth, glabrous. Panicle open, ovoid-oblong, 2–10 cm, 1–2 × as long as wide; branches ascending, 1–3 per node, smooth, longest usually with 5–9 moderately crowded spikelets in distal 1/2. Spikelets ovate to oblong, light green, 3–4 mm, florets 4–6, distal fertile florets often female; vivipary absent; rachilla internodes 1–1.5 mm, smooth, glabrous, often exposed; glumes unequal, margins broadly membranous, smooth, lower glume lanceolate and acute to subflabellate and obtuse, 1–1.5 mm, 1-veined, upper glume elliptic, margin angled, 1.8–2.5 mm, 3-veined; lemmas ovate, membranous-papery, 2–2.5 mm, keel densely villous, marginal and lateral veins densely villous; callus glabrous; palea keels without hooks, densely pilulose to short-villous. Anthers 0.2–0.5 mm, round to short elliptical, less than 1.5 × as long as wide, or vestigial. Fl. and fr. May–Aug. 2n = 14.

Loosely tufted annual; culms 1-25cm high, erect, spreading or prostrate, very slender, compressed. Leaf-blades flat or folded, 0.5-8cm long, 1-2(-4) mm wide, flaccid, abruptly contracted to a blunt or subacute tip, scaberulous on the margins; ligule blunt, up to 3mm long. Panicle ovate-lanceolate, 0.5-10cm long, loose; branches paired or solitary, erecto-patent after anthesis, smooth. Spikelets with (2–)4–6 widely spaced florets, ovate or oblong, 2–4mm long, green; glumes unequal, the lower ovate, 1–1.5mm long, 1–nerved, the upper elliptic or oblong, 1.3-2.5mm long, 1–3–nerved; lemmas oblong in side–view, 2–2.5mm long, blunt, densely hairy on the keel and nerves, without wool at the base; palea as long as the lemma, densely hairy all along the keels; anthers 0.2-0.5mm long, scarcely longer than wide.

Fujian, Shanxi, Sichuan, Zhejiang [India, Pakistan, Tajikistan; Africa, SW Asia, Australia, Europe, Japan, New Zealand, North America, Pacific Islands, South America].

Distribution: Pakistan (Punjab & N. W. F. P.); South America; southern Europe eastwards to the Himalayas and Central Asia.

Fl. & Fr. Per.: March–April.

Sporadic in moist meadows, gardens, sandy places, shady disturbed ground; 1000–2000 m.

Poa annua Linnaeus subsp. exilis (Tommasini ex Freyn) Ascherson & Graebner; P. annua var. exilis Tommasini ex Freyn; P. exilis (Tommasini ex Freyn) Murbeck.

Annuals, Terrestrial, not aquatic, Stems trailing, spreading or pr ostrate, Stems nodes swollen or brittle, Stems erect or ascending, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly basal, below middle of stem, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath or blade keeled, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades very narrow or filiform, less than 2 mm wide, Leaf blades 2-10 mm wide, Leaf blades mostly flat, Leaf blade margins folded, involute, or conduplicate, Leaf blades mostly glabrous, Ligule present, Ligule an unfringed eciliate membrane, Inflorescence terminal, Inflorescence an open panicle, openly paniculate, branches spreading, Inflorescence a contracted panicle, narrow ly paniculate, branches appressed or ascending, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence with 2-10 branches, Inflorescence branches more than 10 to numerous, Flowers bisexual, Spikelets pedicellate, Spikelets laterally compressed, Spikelet less than 3 mm wide, Spikelets with 2 florets, Spikelets with 3-7 florets, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating above the glumes, glumes persistent, Spikelets disarticulating beneath or between the florets, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 2 clearly present, Glumes distinctly unequal, Glumes shorter than adjacent lemma, Glumes keeled or winged, Glumes 1 nerved, Glumes 3 nerved, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma similar in texture to glumes, Lemma 5-7 nerved, Lemma body or surface hairy, Lemma apex truncate, rounded, or obtuse, Lemma awnless, Lemma margins thin, lying flat, Lemma straight, Lemma surface pilose, setose or bristly, Palea present, well developed, Palea about equal to lemma, Palea 2 nerved or 2 keeled, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.

Poa infirma is a species of grass known by the common names early meadow-grass and weak bluegrass. It was first described from a specimen found in Colombia, but it is actually an introduced species in the Americas and is native to Europe. It grows in many types of habitat, including disturbed areas. It is very similar to Poa annua, which is probably a daughter species, and it is often mistaken for P. annua unless it is closely examined.

This is a small, densely tufted annual grass growing up to 15 centimetres (6 in) tall. It has thin, soft-haired, yellow-green leaves. The inflorescence is a series of branches bearing flattened spikelets which have tufts of curly hairs.