Poa annua |
Poa marcida |
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annual blue grass |
weeping bluegrass, withered blue grass |
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Habit | Plants usually annual, rarely surviving for a second season; not rhizomatous, sometimes stoloniferous, densely tufted. | Plants perennial; not rhizomatous, not stoloniferous, sometimes shortly rhizomatous, loosely to densely tufted. |
Culms | 2-20(45) cm, prostrate to erect, slender; nodes terete, usually 1 exserted. |
20-80 cm. |
Sheaths | closed for about 1/3 their length, terete or weakly compressed, smooth; ligules 0.5-3(5) mm, smooth, glabrous, decurrent, obtuse to truncate; blades 1-10 cm long, 1-3(6) mm wide, flat or weakly folded, thin, soft, smooth, margins usually slightly scabrous, apices broadly prow-shaped. |
closed for at least 9/10 their length; ligules 0.5-2 mm, smooth, truncate; blades 1.5-5 mm wide, flat, lax. |
Basal branching | intravaginal, innovations common, similar to the culms. |
mainly pseudointravaginal. |
Panicles | 1-7(10) cm, lengths 1.2-1.6 times widths, erect; nodes with 1-2(3) branches; branches ascending to spreading or reflexed, straight, terete, smooth, with crowded or loosely arranged spikelets. |
6-22 cm, lax, narrowly lanceoloid, sparse; nodes with 1-3 branches; branches ascending, lax, angled, angles scabrous. |
Spikelets | 3-5 mm, laterally compressed; florets 2-6; rachilla internodes smooth, glabrous, concealed or exposed, distal internodes less than 1/2(3/4) the length of the distal lemma. |
3.5-7 mm laterally compressed; florets (1)2(4); rachilla internodes about 1 mm, smooth, glabrous. |
Glumes | smooth, distinctly keeled, keels smooth; lower glumes 1-veined; upper glumes shorter than or subequal to the lowest lemma; calluses glabrous; lemmas 2.5-4 mm, lanceolate, distinctly keeled, smooth throughout, the keels, marginal veins, and, usually, lateral veins crisply puberulent to long-villous, rarely glabrous throughout, lateral veins prominent, intercostal regions glabrous, margins smooth, glabrous, apices obtuse to acute; palea keels smooth, usually short- to long-villous, rarely glabrous; anthers 0.6-1.1 mm, oblong prior to dehiscence, those of the upper 1-2 florets usually vestigial. |
distinctly keeled, keels scabrous; lower glumes 1-veined; upper glumes shorter than or subequal to the lowest lemmas; calluses webbed, webs sparse; lemmas 3.2-5 mm, narrowly lanceolate, distinctly keeled, glabrous, acuminate; palea keels scabrous, sometimes sparsely so; anthers 0.5-1.2 mm. |
2n | = 28. |
= unknown. |
Poa annua |
Poa marcida |
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Distribution |
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; HI; PR; AB; BC; MB; NB; NL; NS; NT; ON; PE; QC; SK; YT; Greenland
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OR; WA; BC |
Discussion | Poa annua is one of the world's most widespread weeds. It thrives in anthropomorphic habitats outside of the arctic. A native of Eurasia, it is now well established throughout most of the Flora region. Poa annua is a gynomonoecious tetraploid (possibly rarely polyhaploid), and is thought to have arisen from hybridization between P. infirma (see next) and P. supina (p. 521) (Tutin 1952). It is similar to P. infirma, differing in having larger anthers. It differs from P. chapmaniana (p. 534) in having glabrous calluses and three larger anthers, rather than one. Forms with glabrous lemmas occur sporadically within populations. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Poa marcida is an uncommon endemic of breaks in rich, mesic, generally old growth forests of the Pacific coast, from Vancouver Island through the western foothills of the northern Cascade Mountains to central Oregon. It differs from P. saltuensis (p. 510) in its closed sheaths and attenuate lemmas. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 24, p. 519. | FNA vol. 24, p. 512. |
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Micrantherae | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Sylvestres |
Sibling taxa | ||
Synonyms | P. annua var. reptans, P. annua var. aquatica | |
Name authority | L. | Hitchc. |
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