Poa lettermanii |
Poa compressa |
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Letterman bluegrass, Letterman's blue grass |
Canada blue grass, Canadian blue grass, flat-stem blue grass |
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Habit | Plants perennial; not glaucous; densely tufted, not stoloniferous, not rhizomatous. | Plants perennial; usually with solitary shoots, sometimes loosely tufted, extensively rhizomatous. |
Culms | 1-12 cm, slender. |
15-60 cm, wiry, bases usually geniculate, strongly compressed; nodes strongly compressed, some proximal nodes usually exserted. |
Sheaths | closed for 1/6 – 1/4 their length, terete; ligules 1-3 mm, milky white to hyaline, smooth; blades 0.5-2 mm wide, flat or folded, or slightly inrolled, thin, without papillae (at 100x), apices narrowly prow-shaped. |
closed for 1/10 – 1/5 their length, distinctly compressed, bases of basal sheaths glabrous; ligules 1-3 mm, moderately to densely scabrous, ciliolate, apices obtuse; blades 1.5-4 mm wide, flat, cauline blades subequal. |
Basal branching | all or mainly intra-vaginal. |
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Panicles | 1-3 cm, erect, contracted, usually exserted from the sheaths; branches to 1.5 cm, erect to steeply ascending, slender, sulcate or angled, smooth or the angles sparsely scabrous; pedicels shorter than the spikelets. |
2-10 cm, generally 1/6 - 1/3 as wide as long, erect, linear, lanceoloid to ovoid, often interrupted, sparse to congested, with 15-80 spikelets and mostly with 1-3 branches per node; branches 0.5-3 cm, erect to ascending, or infrequently spreading, angles densely scabrous, at least in part, with 1-15 spikelets. |
Spikelets | 3-4 mm, laterally compressed, green or anthocyanic; florets 2-3; rachilla internodes shorter than 1 mm, smooth. |
(2.3)3.5-7 mm, laterally compressed; florets 3-7; rachilla internodes usually shorter than 1 mm, smooth to muriculate. |
Glumes | usually equaling or exceeding the lowest lemmas, sometimes also equaling or exceeding the upper florets, lanceolate to broadly lanceolate, distinctly keeled, keels smooth; lower glumes 3-veined; calluses glabrous; lemmas 2.5-3 mm, lanceolate, distinctly keeled, thin, usually glabrous, keels and marginal veins rarely sparsely puberulent proximally, apices acute; palea keels scabrous; anthers 0.2-0.8 mm. |
distinctly keeled; lower glumes 3-veined; calluses usually webbed, sometimes glabrous; lemmas 2.3-3.5 mm, lanceolate, distinctly keeled, keels and marginal veins short-villous, intercostal regions glabrous, lateral veins obscure, margins glabrous, apices acute; paleas scabrous over the keels; anthers 1.3-1.8 mm. |
2n | = 14. |
= 35, 42, 49, 50, 56, 84. |
Poa lettermanii |
Poa compressa |
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Distribution |
CA; CO; ID; MT; NV; OR; UT; WA; WY; AB; BC
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AK; AL; AR; AZ; CA; CO; CT; DC; DE; 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; AB; BC; MB; NB; NL; NS; NT; ON; PE; QC; SK; YT
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Discussion | Poa lettermanii grows on rocky slopes of the highest peaks and ridges in the alpine zone, from northern British Columbia to western Alberta and south to California and Colorado, usually in the shelter of rocks or on mesic to wet, frost-scarred slopes. It is one of only three known diploid Poa species native to the Western Hemisphere. Its glabrous calluses and lemmas usually distinguish it from P. abbreviata (p. 582); it also differs in having flat or folded leaf blades, and shorter spikelets with glumes that are longer than the adjacent florets. Poa montevansii E.H. Kelso is tentatively included here, although its slightly longer lemmas that slightly exceed the glumes suggest that it may represent rare, glabrous forms of P. abbreviata. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Poa compressa is common in much of the Flora region. It is sometimes considered to be native, but this seems doubtful. It is rare and thought to be introduced in Siberia and only local in the Russian Far East, but is common in Europe. In the Flora region, it is often seeded for soil stabilization, and has frequently escaped. It grows mainly in riparian areas, wet meadows, and disturbed ground. Its distinctly compressed nodes and culms, exserted lower culm nodes, rhizomatous growth habit, and scabrous panicle branches make it easily identifiable. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 24, p. 580. | FNA vol. 24, p. 579. |
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Abbreviatae | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Tichopoa |
Sibling taxa | ||
Synonyms | P. mor.tevansi | |
Name authority | Vasey | L. |
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