Poa lettermanii
Poa interior
Letterman bluegrass, Letterman's blue grass
inland bluegrass, interior blue grass, woods blue grass
1-12 cm, slender.
5-80 cm, usually slender, mostly erect or ascending, several to many arising together;
nodes terete or slightly compressed, (0)1-2(3) exserted, top node usually at 1/3 – 3/5 the culm length.
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, terete, bases of basal sheaths glabrous, distal sheath lengths (0.6)0.88-1.64 times blade lengths;
ligules 0.5-1.5(3) mm, sparsely to densely scabrous, apices truncate to obtuse, ciliolate;
blades 0.8-3 mm wide, mostly flat, thin, soft, appressed or abruptly ascending to spreading, straight or somewhat lax, apices narrowly prow-shaped.
all or mainly intra-vaginal.
all or mostly extravaginal.
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.
(1.5)3-15(17) cm, lengths generally 2.5-4 times widths at maturity, usually erect, lax in shade forms, narrowly lanceoloid to ovoid, sparsely to moderately congested;
nodes with 2-5 branches;
branches 0.4-8(9) cm long, 1/4-1/2 the panicle length, ascending to widely spreading, fairly straight, slender to moderately stout, angled, angles moderately to densely scabrous.
3-4 mm, laterally compressed, green or anthocyanic;
florets 2-3;
rachilla internodes shorter than 1 mm, smooth.
3-6 mm, lengths 2-3 times widths, lanceolate to narrowly ovate, laterally compressed, usually not glaucous;
florets (1)2-3(5);
rachilla internodes usually shorter than 1 mm, smooth, muriculate, or scabrous, glabrous, hispidulous, or sparsely to densely puberulent, proximal internodes frequently curved.
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.
lanceolate to broadly lanceolate, distinctly keeled, keels smooth or sparsely scabrous;
lower glumes 3-veined, long- or abruptly tapered to a slender point, lengths 4.5-6.3 times widths;
calluses usually webbed, infrequently glabrous in depauperate alpine specimens, webs usually scant, less than 1/2(2/3) the lemma length, frequently minute;
lemmas 2.4-4 mm, lanceolate, distinctly keeled, straight or gradually arched, not abruptly inwardly arched at the junction with the scarious apices, keels and marginal veins short-villous, hairs extending 2/3 – 3/4 the keel length, lateral veins usually glabrous, rarely sparsely puberulent, obscure, intercostal regions smooth, sometimes weakly muriculate, glabrous, margins not or slightly inrolled, glabrous, apices acute, usually partially bronze-colored;
palea keels scabrous, intercostal regions glabrous;
anthers (1.1)1.3-2.5 mm.
= 14.
= 28, 42, 56.
Poa lettermanii
Poa interior
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 interior, a native species, grows from Alaska to western Quebec and New York, south to Arizona and New Mexico. It is restricted to the Flora region. It is fairly common from boreal forests to low alpine habitats of the Rocky Mountains. It grows in subxeric to mesic habitats, such as mossy rocks and scree, usually in forests. It is usually tetraploid.
In alpine habitats, Poa interior is often quite short, and often sympatric with P. glauca (see next). It is most reliably distinguished from P. glauca by lemmas that are glabrous between the marginal veins and keels or, rarely, sparsely puberulent on the lateral veins. It usually also differs from P. glauca subsp. rupicola in having at least a few hairs on its calluses. It can be distinguished from P. nemoralis (see previous) by its longer ligules, lower top culm node, and wider glumes and lemmas. It is sometimes difficult to distinguish from P. palustris (p. 574), but differs in having lemmas with wider hyaline margins and straight or gradually arched keels, a densely tufted habit, and scantly webbed calluses.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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