Poa lettermanii |
Poa tenerrima |
|
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Letterman bluegrass, Letterman's blue grass |
delicate blue grass |
|
Habit | Plants perennial; not glaucous; densely tufted, not stoloniferous, not rhizomatous. | Plants perennial; densely tufted, basal leaf tufts 2-8(13) cm, small, narrowly based, not stoloniferous, not rhizomatous. |
Culms | 1-12 cm, slender. |
15-50 cm tall, slender, 0.8-0.9 mm thick; nodes terete, 0-1 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 76-74 their length, terete, scabrous, glabrous, bases of basal sheaths glabrous, distal sheath lengths 2.3-7.7 times blade lengths; collars sparsely scabrous, glabrous; ligules 0.5-1.5(2.5) mm, scabrous, apices usually truncate to obtuse, sometimes acute, ligules of innovations to 0.5 mm; innovation blades filiform; cauline blades gradually reduced in length upwards, 0.4-1.5 mm wide, mostly folded, thin, soft, soon withering, scabrous, apices narrowly prow-shaped. |
Basal branching | all or mainly intra-vaginal. |
intravaginal. |
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. |
5-15 cm, 1.3-2.2 times the branch lengths, erect, broadly rhomboidal to pyramidal, open, purple, sparse, proximal internodes 1.5-4.2 cm; nodes with 1-2(5) branches; branches 3-8.5 cm, widely spreading, capillary, straight, terete to weakly angled, moderately to mostly densely scabrous, with 3-9 spikelets in the distal 73. |
Spikelets | 3-4 mm, laterally compressed, green or anthocyanic; florets 2-3; rachilla internodes shorter than 1 mm, smooth. |
5-8 mm, lengths (3.8)4-5 times widths, usually narrowly lanceolate to lanceolate, subterete to weakly laterally compressed, drab, usually strongly anthocyanic; florets 3-5; rachilla internodes 1-1.5+ mm, terete or slightly dorsally compressed, muriculate or scabrous. |
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. |
lanceolate, distinctly shorter than the adjacent lemmas, scabrous distally, keels indistinct, scabrous, obtuse to acute; lower glumes 3-veined; calluses glabrous or with a crown of hairs, hairs to 0.3 mm; lemmas 3-4.2 mm, lanceolate, weakly keeled, keels, veins, and proximal 2/3 of the intercostal regions puberulent, lateral veins obscure, margins strongly inrolled below, broadly scarious above, glabrous, apices obtuse to acute; palea keels scabrous, sometimes hairy at midlength; anthers 1.6-2.1 mm. |
2n | = 14. |
= 42. |
Poa lettermanii |
Poa tenerrima |
|
Distribution |
CA; CO; ID; MT; NV; OR; UT; WA; WY; AB; BC
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CA |
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 tenerrima is a rare species, endemic to serpentine barrens along the western base of the Sierra Nevada. It differs from P. secunda subsp. secunda (see previous) in combining consistently wide, open panicles, very scabrous branches, short-truncate ligules, and very fine foliage. A series of small, delicate, open-panicled plants from the California Coast Ranges, formerly included in P. tenerrima by Soreng (1993), differ in having smooth branches and longer ligules, and are better referred to P. secunda subsp. secunda. No intergradation is evident where the two taxa grow together. Plants from the Columbia River Gorge in Oregon, including the type of P. multnomae Piper, approach P. tenerrima, but are presumed to be derived from hybridization between P. nervosa (p. 545) and P. secunda (p. 586). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 24, p. 580. | FNA vol. 24, p. 588. |
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Abbreviatae | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Secundae > subsect. Secundae |
Sibling taxa | ||
Synonyms | P. mor.tevansi | |
Name authority | Vasey | Scribn. |
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