Poa cusickii |
Poa wheeleri |
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Cusick's bluegrass |
Hooker's bluegrass, Wheeler's blue grass |
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Habit | Plants perennial; usually densely tufted, rarely moderately densely tufted, usually neither rhizomatous nor stoloniferous, infrequently short-rhizomatous or stoloniferous, rarely with distinct rhizomes. | Plants perennial; densely to loosely tufted or with solitary shoots, shortly rhizomatous. | ||||||||||||
Culms | 10-60(70) cm tall, 0.5-1.8 mm thick, erect or the bases decumbent, terete or weakly compressed; nodes terete, 0-2 exserted. |
35-80 cm, erect or the bases decumbent, terete or weakly compressed; nodes terete, 1-2 exserted. |
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Sheaths | closed for 1/4-3/4 their length, terete, smooth or scabrous, glabrous, bases of basal sheaths glabrous, distal sheath lengths 1.6-10 times blade lengths; collars smooth or scabrous, glabrous; ligules of cauline leaves 1-3(6) mm, smooth or scabrous, truncate to acute, ligules of the innovation leaves 0.2-0.5(2.5) mm, scabrous, usually truncate; innovation blades sometimes distinctly different from the cauline blades, 0.5-2 mm wide, involute, moderately thick, moderately firm, adaxial surfaces usually densely scabrous or hispidulous to softly puberulent, infrequently nearly smooth and glabrous; cauline blades subequal or the midcauline blades longest or the blades gradually reduced in length distally, 0.5-3 mm wide, flat, folded, or involute, usually thin, usually withering, abaxial surfaces smooth or scabrous, apices narrowly to broadly prow-shaped, flag leaf blades 0.5-5(6) cm. |
closed for 1/3-1/4 their length, terete to slightly compressed, at least some proximal sheaths densely retrorsely scabrous, hispidulous, or softly puberulent for the upper 1/4 of their length, bases of basal sheaths glabrous, distal sheath lengths (1.4)1.7-4.6(6.2) times blade lengths; collars of proximal leaves glabrous or with hairs the same length as those of their sheaths; ligules 0.5-2 mm, smooth or scabrous, sometimes puberulent, truncate, those of the lower culm and innovation leaves 0.5-1.5 mm, abaxial surfaces scabrous to softly puberulent, truncate; innovation blades folded or involute, infrequently flat, moderately thick, soft, adaxial surfaces usually densely scabrous to hispidulous; cauline blades 2-3.5 mm wide, flat or folded, smooth or sparsely scabrous, glabrous or hispidulous, apices narrowly to broadly prow-shaped, blades gradually reduced distally or the middle blades longest, flag leaf blades 1-10 cm long. |
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Basal branching | intravaginal or intra- and extravaginal. |
mainly extra-vaginal. |
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Panicles | 2-10(12) cm, usually erect, contracted or loosely contracted, narrowly lanceoloid to ovoid, congested or moderately congested, with 10-100 spikelets and 1-3(5) branches per node; branches 0.5-4(5) cm, erect or steeply ascending, fairly straight, slender to stout, terete to angled, smooth or scabrous, with 1-15 spikelets. |
5-12(18) cm, erect or nodding, ovoid to pyramidal, loosely contracted to open, with 20-70 spikelets, proximal internodes usually shorter than 3.5 cm; nodes with 2-5 branches; branches (1)1.7-6.5 cm, ascending to spreading or reflexed, lax, terete or weakly angled, sparsely to moderately scabrous, with 2-8(12) spikelets. |
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Spikelets | (3)4-10 mm, lengths to 3 times widths, broadly lanceolate to narrowly ovate, laterally compressed, not sexually dimorphic; florets 2-6; rachilla internodes 0.5-1.2 mm, smooth or scabrous. |
5.5-10 mm, lengths to 3.5 times widths, laterally compressed, not sexually dimorphic; florets 2-7; rachilla internodes smooth or scabrous, glabrous or sparsely to densely hispidulous. |
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Glumes | lanceolate, distinctly keeled; lower glumes 3-veined, distinctly shorter than the lowest lemmas; calluses glabrous or diffusely webbed, hairs less than 1/4 the lemma length; lemmas (3)4-7 mm, lanceolate to broadly lanceolate, distinctly keeled, membranous to thinly membranous, smooth or sparsely to densely scabrous, glabrous or the keels and/or marginal veins puberulent proximally, lateral veins obscure to prominent, margins glabrous, apices acute; palea keels scabrous, intercostal regions glabrous; anthers vestigial (0.1-0.2 mm), aborted late in development, or 2-3.5 mm. |
1/4 - 2/3(3/4) as long as the adjacent lemmas, lanceolate, distinctly keeled; lower glumes 1-3-veined, 1/4-1/2 as long as the adjacent lemmas; calluses glabrous; lemmas 3-6 mm, lanceolate, distinctly keeled, keels and marginal veins glabrous or softly puberulent to short-villous, intercostal regions glabrous or hispidulous, infrequently puberulent, smooth or finely scabrous, lateral veins obscure to moderately prominent, margins glabrous, apices acute; palea keels scabrous, intercostal regions glabrous; anthers usually vestigial (0.1-0.2 mm) or aborted late in development and up to 2 mm, rarely normal. |
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2n | = 28, 28+11, 56, 56+11, 59, ca. 70. |
= 56, 61, 62, 63, 64, 66, 61, 70, ca. 74, 75, 79, 80, 81, 87, 89, 90, 91. |
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Poa cusickii |
Poa wheeleri |
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Distribution |
CA; CO; ID; MT; ND; NV; OR; UT; WA; WY; AB; BC; MB; SK; YT
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CA; CO; ID; MT; NM; NV; OR; UT; WA; WY; AB; BC; MB; SK
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Discussion | Poa cusickii grows in rich meadows in sagebrush scrub to rocky alpine slopes, from the southwestern Yukon Territory to Manitoba and North Dakota, south to central California and eastern Colorado. It is gynodioecious or dioecious. Sexually reproducing plants of Poa cusickii subspp. cusickii and pallida grow in different geographic areas, but pistillate plants of these two subspecies have overlapping ranges. Only pistillate plants are known in Poa cusickii subspp. epilis and purpurascens. All the alpine plants studied were pistillate. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Poa wheeleri is common at mid- to high elevations, generally on the east side of the coastal mountains from British Columbia to California, and from Manitoba to New Mexico. It generally grows in submesic coniferous forests to subalpine habitats. Most plants have densely retrorsely pubescent or scabrous sheaths, involute innovation blades that are pubescent adaxially, and pistillate florets. Poa wheeleri, a high polyploid apomictic species, probably arose from hybridization between P. cusickii (p. 559) and another member of the Poa nervosa complex. It resembles P. rhizomata (see next) and P. chambersii (p. 548) more than P. nervosa sensu stricto (see previous). It differs from P. chambersii in having at least some proximal sheaths that are densely retrorsely scabrous or pubescent (sometimes obscurely so), and folded or involute innovation blades that are scabrous to hispidulous on the adaxial surfaces. For a comparison with P. nervosa, see p. 545. Natural hybrids have been found between P. wheeleri and P. pratensis (p. 522). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 24, p. 559. | FNA vol. 24, p. 546. | ||||||||||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Madropoa > subsect. Epiles | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Madropoa > subsect. Poa | ||||||||||||
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Synonyms | P. nervosa var. wheeleri, P. curta | |||||||||||||
Name authority | Vasey | Vasey | ||||||||||||
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