Poa arctica |
Poa bigelovii |
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arctic bluegrass |
Bigelow bluegrass, Bigelow's blue grass |
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Habit | Plants perennial; usually strongly anthocyanic; rhizomatous, rhizomes usually well developed, sometimes poorly developed, shoots usually solitary. | Plants usually annual, rarely longer-lived; densely tufted, tuft bases narrow, usually without sterile shoots, not stolonigerous, not rhizomatous. | ||||||||||||||||
Culms | 7.5-60 cm, slender to stout, terete or weakly compressed, bases usually decumbent, not branching above the bases; nodes terete, proximal nodes usually not exserted, 0-2 exserted above. |
(2)5-60(70) cm tall, 0.3-1 mm thick, usually erect, bases rarely geniculate; nodes terete, usually 1 exserted. |
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Sheaths | closed for (1/6)1/5 – 2/5 their length, terete, glabrous, smooth or sparsely scabrous, bases of basal sheaths glabrous, distal sheath lengths 1.4-4(5.3) times blade lengths; collars smooth, glabrous; ligules (1)2-7 mm, glabrous, smooth or sparsely to infrequently moderately scabrous, apices usually rounded to obtuse or acute, rarely truncate, entire or lacerate; blades 1-6 mm wide, flat or folded, somewhat involute, smooth, glabrous, apices broadly prow-shaped, cauline blades subequal or gradually reduced distally, flag leaf blades 0.7-9 cm. |
closed for 1/4 - 1/2 their length, usually compressed and keeled, smooth or the keels scabrous; ligules 2-6 mm, smooth or scabrous, usually decurrent, obtuse to acute; blades 1.5-5 mm wide, flat, thin, soft, finely scabrous, apices broadly prow-shaped, cauline blades (1)4-15 cm, flag leaf blades usually 1-4 cm. |
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Basal branching | mainly extravaginal. |
intravaginal. |
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Panicles | (2)3.5-15 cm, ovoid to broadly pyramidal, usually open, sparse, with 10-40(60) spikelets, proximal internodes shorter than 1.5(3) cm, with (1)2-5 branches per node; branches 1.5-6 cm, spreading soon after emergence from the sheath, thin, sinuous, and flexuous to fairly stout and straight, terete, smooth or sparsely to infrequently moderately scabrous, with (1)2-5 spikelets, the spikelets not crowded. |
(1)5-15 cm, erect, cylindrical, contracted, sometimes interrupted, congested, with 2-3(5) branches per node; branches erect or steeply ascending, smooth or sparsely to densely scabrous. |
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Spikelets | (3.5) 4.5-8 mm, lengths to 3.5 times widths, laterally compressed, sometimes bulbiferous; florets (2)3-6, infrequently bulb-forming; rachilla internodes smooth or muriculate, proximal internodes glabrous or sparsely softly puberulent to long-villous. |
4-7 mm, laterally compressed; florets 3-7; rachilla internodes to 1 mm, smooth, glabrous. |
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Glumes | lanceolate to broadly lanceolate, distinctly or weakly keeled, keels usually smooth, sometimes sparsely scabrous distally, lateral veins usually moderately pronounced; lower glumes (3)3.5-5(6) mm, 3-veined; upper glumes 3.5-5.5(6.5) mm, nearly equaling to slightly exceeding the lowest lemmas, or distinctly shorter; calluses glabrous or webbed, hairs sparse and short to over 1/3 – 2/3 the lemma length; lemmas (2.7)3-6(7) mm, lanceolate to broadly lanceolate, usually strongly purple, distinctly keeled, keels, marginal veins, and lateral veins long-villous, hairs on the lateral veins sometimes shorter, lateral veins prominent, intercostal regions short-villous to softly puberulent at least near the base, glabrous elsewhere, smooth to weakly muriculate and/or usually sparsely scabrous, infrequently moderately scabrous, margins broadly hyaline, glabrous, apices acute; palea keels usually short- to long-villous for most of their length, rarely nearly glabrous and scabrous, intercostal regions broad, usually at least sparsely softly puberulent, rarely glabrous, apices scabrous; anthers 1.4-2.5 mm, sometimes aborted late in development. |
subequal, distinctly keeled, keels and sometimes the lateral veins scabrous; lower glumes 1(3)-veined; upper glumes shorter than or subequal to the lowest lemmas; calluses webbed; lemmas 2.6-4.2 mm, lanceolate, distinctly keeled, smooth, keels, marginal veins, and sometimes the lateral veins short- to long-villous, keels hairy to near the apices, marginal veins to 2/3 their length, lateral veins obscure to moderately prominent, intercostal regions glabrous or softly puberulent, upper margins white, apices acute; palea keels softly puberulent to short-villous at midlength, scabrous near the apices, intercostal regions usually softly puberulent; anthers 1-3, 0.2-1 mm. |
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2n | = 36, 42, 56, 60, 62-68, 70, ca. 72, 74-76, 78-80, 82-84, 86, 88, 99, 106. |
= 28, 28+1. |
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Poa arctica |
Poa bigelovii |
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Distribution |
AK; CO; ID; MT; NM; NV; UT; WA; WY; AB; BC; MB; NL; NT; NU; ON; QC; SK; YT; Greenland
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AZ; CA; CO; NM; NV; OK; TX; UT
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Discussion | Poa arctica is a common circumboreal species of arctic and alpine regions, growing mainly in mesic to subhydric, acidic tundra and alpine meadows, and on rocky slopes. It extends south in the Rocky Mountains to New Mexico. The frequency of sterile anthers in plants of the high arctic suggests that P. arctica is sometimes apomictic in that region. Over most of the rest of its range, P. arctica usually develops normal anthers. This and isozyme data for populations from alpine and low arctic regions suggest sexual reproduction is common in these habitats. The most reliable way to distinguish Poa arctica from P. pratensis (p. 522), particularly subsp. alpigena, is by the wider paleas and the presence of hairs between the palea keels. Bulbiferous forms of P. arctica differ from P. stenantha var. vivipara (p. 594) in not being glaucous, and in having rhizomes and terete, smooth panicle branches. Poa xgaspensis (p. 601) also resembles P. arctica, but it has sharply keeled, more scabrous glumes and a spikelet shape that is intermediate between P. pratensis and P. alpina (p. 518). Poa arctica forms natural hybrids with both P. pratensis and P. secunda (p. 586). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Poa bigelovii grows in arid upland regions, particularly on shady, rocky slopes of the southwestern United States and northern Mexico. Plants from southeastern Arizona eastwards are usually glabrous between the lemma veins, whereas more western plants are usually puberulent between the lemma veins. Plants with 1 or 2 small anthers are found in the eastern portion of the species' range; they differ from P. chapmaniana (p. 534) in their persistently contracted panicles and broader leaf blades. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 24. | FNA vol. 24, p. 536. | ||||||||||||||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Poa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Homalopoa | ||||||||||||||||
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Name authority | R. Br. | Vasey & Scribn. | ||||||||||||||||
Web links |