Poa nemoralis |
Poa infirma |
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Eurasian woodland bluegrass, forest blue grass, interior bluegrass (ssp. interior), wood blue grass, woodland bluegrass, woods bluegrass (ssp. nemoralis) |
diploid annual bluegrass, weak blue grass |
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Habit | Plants perennial; green or glaucous; densely tufted, not stoloniferous, not rhizomatous. | Plants annual; neither rhizomatous nor stoloniferous, densely tufted. |
Culms | 30-80 cm, mostly erect, smooth below the panicles; nodes slightly compressed, 2-5 exserted, top node at 1/2 - 3/4 the culm length. |
2-15 cm, prostrate to erect, slender; nodes terete, usually 1 exserted. |
Sheaths | closed for 1/10 – 1/5 their length, terete, bases of basal sheaths glabrous, distal sheath lengths 0.45-1 (1.1) times blade lengths; ligules 0.2-0.8(1) mm, sparsely to densely scabrous, apices truncate, minutely ciliolate; blades 0.8-3 mm wide, mostly flat, appressed, abruptly ascending to spreading, straight or somewhat lax, apices narrowly prow-shaped. |
closed for about 1/3 their length, terete or weakly compressed, smooth; ligules 0.5-3 mm, smooth, glabrous, decurrent, obtuse to truncate; blades 1-3(4) mm wide, flat, thin, soft, smooth, margins usually slightly scabrous, apices broadly prow-shaped. |
Basal branching | all or mostly extravaginal. |
intravaginal, sterile shoots common, similar to the culms. |
Panicles | 7-16(20) cm, lengths usually 2.5-4 times widths at maturity, usually erect, lax in shade forms, narrowly lanceoloid to ovoid, slightly to moderately congested; nodes with 2-5 branches; branches ascending to widely spreading, fairly straight, slender to moderately stout, angled, angles moderately to densely scabrous. |
1-6 cm, lengths 1.5-3 times widths, erect; nodes with 1-2(5) branches; branches ascending, straight, terete, smooth, with crowded spikelets. |
Spikelets | 3-8 mm, lengths 2.5-3.5 times widths, narrowly lanceolate to lanceolate, laterally compressed, usually not glaucous; florets (1)2-5; rachilla internodes usually shorter than 1 mm, smooth, muriculate, or scabrous, usually puberulent, infrequently hispidulous or glabrous. |
3-5 mm, laterally compressed; florets 2-6; rachilla internodes smooth, glabrous, usually exposed in side view, distal internodes 1/2 - 3/4 the length of tbe distal lemma. |
Glumes | subulate to narrowly lanceolate, distinctly keeled, keels smooth or sparsely scabrous, apices sharply acute to acuminate; lower glumes 3-veined, long-tapered to a slender point, lengths 6.4-11 times widths; upper glumes shorter than or subequal to the lowest lemmas; calluses webbed, hairs sparse, often short; lemmas 2.4-4 mm, proximal lemma widths less than 1/5 times lengths, narrowly lanceolate to lanceolate, distinctly keeled, keels and marginal veins short-villous, lateral veins glabrous, obscure, intercostal regions smooth or muriculate, glabrous, margins glabrous, apices acute, usually partially bronze-colored; palea keels scabrous, intercostal regions glabrous; anthers 0.8-1.9 mm. |
smooth, distinctly keeled, keels smooth; lower glumes 1-veined; upper glumes shorter than or subequal to the lowest lemmas; calluses glabrous; lemmas 2-2.5 mm, lanceolate, distinctly keeled, smooth throughout, the keels, marginal and lateral veins crisply puberulent to long-villous, lateral veins prominent, intercostal regions glabrous, margins smooth, glabrous, apices obtuse to acute; palea keels smooth, short- to long-villous; anthers 0.1-0.6 mm, more or less spherical to short-elliptical prior to dehiscence, those of the upper 1-2 florets commonly vestigial. |
2n | = 28, 35, 42, 48, 50, 56. |
= 14. |
Poa nemoralis |
Poa infirma |
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Distribution |
AK; AZ; CA; CO; CT; DE; IA; ID; IL; IN; KY; MA; MD; ME; MI; MN; MO; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OR; PA; RI; SD; TN; TX; UT; VA; VT; WA; WI; WY; AB; BC; MB; NB; NL; NS; NT; ON; QC; SK; YT; Greenland
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CA; OR; SC; BC |
Discussion | Introduced from northern Eurasia, Poa nemoralis is established primarily at low elevations in deciduous and mixed conifer/deciduous forests. It is now common in southeastern Canada and the northeastern United States, and is spreading in the west. It can be distinguished from P. glauca (p. 576) and P. interior (see next) by its consistently short ligules, high top culm node, relatively long flag leaf blades, and narrow glumes and lemmas. It is usually hexaploid. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Poa infirma was introduced from Europe to the Americas, and was first described from Colombia. It is sporadically established along the Pacific coast and in the central valleys of California, and has been collected in Charleston, South Carolina. It is rare elsewhere in the Flora region. Poa annua often resembles P. infirma (see previous), which is thought to be one of its parents, but P. annua is tetraploid and has anthers 0.6-1.1 mm long. Both species are gynomonoecious. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 24, p. 574. | FNA vol. 24, p. 519. |
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Stenopoa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Micrantherae |
Sibling taxa | ||
Name authority | L. | Kunth |
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