Poa lettermanii
Poa sylvestris
Letterman bluegrass, Letterman's blue grass
woodland bluegrass
1-12 cm, slender.
30-120 cm, bases often decumbent.
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 (1/20) 1/2-7/8 their length, terete, throats frequently ciliate near the point of fusion;
ligules 0.5-2.7 mm, smooth or sparsely scabrous, truncate to obtuse;
blades 0.7-5 mm wide, flat, thin, lax.
all or mainly intra-vaginal.
mainly pseudointravaginal.
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.
(6.7)9-20 cm, open, narrowly conical at maturity;
nodes with (2)3-10 branches per node;
branches (2)3-7 cm, spreading to eventually reflexed, straight, angled, angles several, densely scabrous, with 1-11 spikelets.
3-4 mm, laterally compressed, green or anthocyanic;
florets 2-3;
rachilla internodes shorter than 1 mm, smooth.
2.5-4.4 mm, laterally compressed;
florets 2-3(4);
rachilla internodes longer than (1)1.2 mm, smooth, glabrous.
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, keels scabrous;
lower glumes 1(3)-veined;
upper glumes shorter than or subequal to the lowest lemmas;
calluses webbed;
lemmas 2.1-3.1 mm, broadly lanceolate, distinctly keeled, keels and marginal veins short-villous, extending to near the apices on the keels, lateral veins prominent, softly puberulent to short-villous, intercostal regions usually sparsely softly puberulent, smooth, apices obtuse to acute;
palea keels softly puberulent at midlength, apices finely scabrous;
anthers 1-1.8 mm.
= 14.
= 28.
Poa lettermanii
Poa sylvestris
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 sylvestris grows in southeastern Canada and throughout much of the eastern United States, mainly at low elevations in woodlands, especially in riparian zones. It is easily distinguished from P. wolfii (p. 514) by its smaller, more numerous spikelets and lemmas that are usually sparsely hairy between the veins. Plants from the middle Appalachian Mountains have been confused with P. paludigena (p. 572); P. sylvestris is usually larger, has more than 2 branches per panicle node, is pubescent between the lemma veins and palea keels, and has larger anthers.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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