Poa cusickii |
Poa tracyi |
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Cusick's bluegrass |
Tracy's bluegrass |
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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; loosely tufted, 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. |
(25)32-125 cm, erect or the bases decumbent, not branching above the base, terete or weakly compressed; nodes terete or slightly compressed, 1-2(3) 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 (2/5)1/2 – 9/10 their length, compressed, distinctly keeled, keels winged, wing to 0.5 mm wide, smooth or sparsely to infrequently densely scabrous, glabrous or infrequently retrorsely pubescent, bases of basal sheaths glabrous, distal sheath lengths 0.7-1.6 times blade lengths; collars with vestiture similar to the sheaths; ligules 2-4.5 mm, smooth or scabrous, glabrous or softly puberulent, obtuse to acute; innovation blades similar to the cauline blades; cauline blades (1.5)2-5.5 mm wide, flat, lax, smooth or sparsely scabrous mainly over the veins, apices broadly prow-shaped, flag leaf blades 6-20 cm. |
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Basal branching | intravaginal or intra- and extravaginal. |
mainly extravaginal. |
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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. |
(8)13-29 cm, erect, usually narrowly pyramidal, open, sparse, with 30-100 spikelets, proximal internodes usually 4+ cm, with (1)2-4(5) branches per node; branches 2.5-18 cm, spreading to eventually reflexed, fairly flexuous, terete to weakly angled, sparsely to moderately scabrous, with 3-34 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. |
3-8 mm, lengths 3.5 times widths, laterally compressed, not sexually dimorphic; florets 2-8; rachilla internodes 1+ mm, smooth, glabrous. |
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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. |
narrowly lanceolate, distinctly keeled; lower glumes 1.6-3.5 mm, 1(3)-veined, 1/2-1/3 as long as the adjacent lemmas; upper glumes 2.2-4.9 mm; calluses webbed, hairs over 1/2 the lemma length; lemmas 2.6-5 mm, lanceolate, distinctly keeled, keels and marginal veins long-villous, extending 1/2 - 2/3 the keel length, 1/3-1/2 the marginal vein length, lateral veins sometimes short-villous, the lateral veins obscure to moderately prominent, intercostal regions usually sparsely softly puberulent, margins glabrous, apices acute; palea keels scabrous, rarely softly puberulent at midlength; anthers vestigial (0.1-0.2 mm) or (1.3)2-3 mm. |
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2n | = 28, 28+11, 56, 56+11, 59, ca. 70. |
= 28, 28+1. |
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Poa cusickii |
Poa tracyi |
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Distribution |
CA; CO; ID; MT; ND; NV; OR; UT; WA; WY; AB; BC; MB; SK; YT
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CO; NM |
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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 tracyi grows primarily in coniferous forest openings, sometimes with gambel oak, and in subalpine mesic meadows. It is restricted to the front ranges of the southern Rocky Mountains; it is not common. It differs from P. occidentalis (p. 536) in having longer and/or rudimentary anthers, shorter ligules relative to the leaf blade width, and a loose, shortly rhizomatous habit. Retrorsely pubescent sheaths are common in the more southern plants. It is sequentially gynomonoecious. (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. 543. | ||||||||||||
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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Name authority | Vasey | Vasey | ||||||||||||
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