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Letterman bluegrass, Letterman's blue grass

Habit Plants perennial; not glaucous; densely tufted, not stoloniferous, not rhizomatous. Plants perennial; densely tufted, not stoloniferous, not rhizomatous.
Culms

1-12 cm, slender.

usually shorter than 25(30) cm, slender, terete;

nodes terete.

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.

Basal branching

all or mainly intra-vaginal.

mainly intravaginal.

Leaves

mostly basal;

sheaths closed for 1/10 – 1/4(1/3) their length, terete;

ligules 0.4-5.5 mm, milky white to hyaline, smooth or scabrous, apices truncate to acute, glabrous;

blades 0.5-2 mm wide, flat, folded, or involute, thin to moderately thick, soft or moderately firm, apices narrowly prow-shaped.

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.

1-7 cm, erect, usually contracted, sometimes open;

nodes with 1-3 branches;

branches 0.5-1.5(5) cm, usually erect to steeply ascending, sometimes ascending to spreading, sulcate to angled, smooth or the angles sparsely to densely scabrous.

Spikelets

3-4 mm, laterally compressed, green or anthocyanic;

florets 2-3;

rachilla internodes shorter than 1 mm, smooth.

3-7 mm, laterally compressed, rarely bulbiferous;

florets 2-5, usually bisexual, sometimes with vestigial anthers or anthers that abort late in the growing season, rarely bulb-forming;

rachilla internodes usually glabrous, infrequently sparsely hispidulous.

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.

usually subequal to or slightly longer than the adjacent lemmas, distinctly keeled, keels smooth or sparsely scabrous;

lower glumes (1)3-veined;

calluses terete or slightly laterally compressed, glabrous or dorsally webbed;

lemmas 2-5.8 mm, lanceolate to broadly lanceolate, distinctly keeled, thin, glabrous or the keels and marginal veins softly puberulent to long-villous, intercostal regions glabrous or softly puberulent to short-villous, obscurely 5-veined;

palea keels scabrous, glabrous or softly puberulent to short-villous at midlength;

anthers 3, 0.2-1.3(1.8) mm, rarely vestigial (0.1-0.2 mm) or aborted late in development.

2n

= 14.

Poa lettermanii

Poa sect. Abbreviatae

Distribution
from FNA
CA; CO; ID; MT; NV; OR; UT; WA; WY; AB; BC
[WildflowerSearch map]
[BONAP county map]
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 sect. Abbreviatae includes five North American species, two of which also grow in arctic regions of the Eastern Hemisphere. The species are principally high alpine to high arctic. Two of the species are known or reputed to be diploid.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 24, p. 580. FNA vol. 24.
Parent taxa Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Abbreviatae Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa
Sibling taxa
P. abbreviata, P. alpina, P. alsodes, P. ammophila, P. annua, P. arachnifera, P. arctica, P. arida, P. arnowiae, P. atropurpurea, P. autumnalis, P. bigelovii, P. bolanderi, P. bulbosa, P. chaixii, P. chambersii, P. chapmaniana, P. compressa, P. confinis, P. curtifolia, P. cusickii, P. cuspidata, P. diaboli, P. douglasii, P. eminens, P. fendleriana, P. glauca, P. hartzii, P. howellii, P. infirma, P. interior, P. keckii, P. kelloggii, P. laxa, P. laxa × glauca, P. laxiflora, P. leibergii, P. leptocoma, P. macrantha, P. macrocalyx, P. marcida, P. napensis, P. nemoralis, P. nervosa, P. occidentalis, P. paludigena, P. palustris, P. paucispicula, P. piperi, P. porsildii, P. pratensis, P. pringlei, P. pseudoabbreviata, P. reflexa, P. rhizomata, P. saltuensis, P. secunda, P. sierrae, P. stebbinsii, P. stenantha, P. strictiramea, P. sublanata, P. suksdorfii, P. supina, P. sylvestris, P. tenerrima, P. tracyi, P. trivialis, P. unilateralis, P. wheeleri, P. wolfii, P. ×gaspensis, P. ×limosa, P. ×nematophylla
Subordinate taxa
Synonyms P. mor.tevansi
Name authority Vasey Nannf. ex Tzvelev
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