Poa annua |
Poa ×limosa |
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annual blue grass |
hybrid bluegrass, Lassen County bluegrass |
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Habit | Plants usually annual, rarely surviving for a second season; not rhizomatous, sometimes stoloniferous, densely tufted. | Plants perennial; densely to loosely tufted or the culms solitary, shortly rhizomatous. |
Culms | 2-20(45) cm, prostrate to erect, slender; nodes terete, usually 1 exserted. |
20-80 cm, erect or the bases decumbent. |
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. |
usually closed for about 1/6 their length; ligules 1-4 mm, smooth or sparsely scabrous, apices obtuse to acute; innovation blades 0.5-2 mm wide; cauline blades 0.5-5 mm wide, flat, folded, abaxial surfaces smooth or scabrous, apices narrowly prow-shaped. |
Basal branching | intravaginal, innovations common, similar to the culms. |
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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. |
5-15 cm, erect, usually contracted, sometimes interrupted; branches shorter than 4 cm, erect, angles somewhat 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. |
4-7 mm, weakly laterally compressed; florets 2-5; rachilla internodes smooth. |
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. |
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Lower | glumes 3-veined; calluses glabrous or webbed, hairs to 1/4 the lemma length; lemmas 2.5-4.5 mm, narrowly lanceolate, distinctly to weakly keeled, glabrous throughout or the keels and marginal veins sparsely long-villous, apices acute; palea keels scabrous; anthers aborted late in development or 1.3-2.2 mm. |
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2n | = 28. |
= 64. |
Poa annua |
Poa ×limosa |
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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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CA; OR; AB; BC; SK |
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 xlimosa grows at scattered locations in western North America. It prefers wet to moist, often saline or alkaline meadows, primarily in the sagebrush zone. It is probably a hybrid between P. pratensis (p. 522) and P. secunda subsp. juncifolia (p. 586). Vigorous artificial hybrids of this parentage have been produced; they resemble P. xlimosa. Poa ×limosa is a named intersectional hybrid (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 24, p. 519. | FNA vol. 24, p. 601. |
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Micrantherae | Poaceae > subfam. Pooideae > tribe Poeae > Poa |
Sibling taxa | ||
Synonyms | P. annua var. reptans, P. annua var. aquatica | |
Name authority | L. | Scribn. & T.A. Williams |
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