Poa arctica |
Poa confinis |
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arctic bluegrass |
beach blue grass, coastal bluegrass, coastline blue grass |
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Habit | Plants perennial; usually strongly anthocyanic; rhizomatous, rhizomes usually well developed, sometimes poorly developed, shoots usually solitary. | Plants perennial; densely to loosely tufted, rhizomatous and stoloniferous, rhizomes and stolons to 1 m, slender. | ||||||||||||||||
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. |
7-30 (35) cm tall, 0.4-0.9 mm thick, slender, erect or the bases decumbent, terete or weakly compressed; nodes terete, 0-1 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 1/3-2/3 their length, terete, smooth, glabrous, bases of basal sheaths glabrous, distal sheath lengths (1)1.4-4.5 times blade lengths; collars smooth, glabrous; ligules 0.5-1.5(2.2) mm, scabrous, truncate to acute; innovation blades adaxially moderately to densely scabrous or hispidulous on and between the veins; cauline blades slightly reduced in length distally, 0.5-1(1.5) mm wide, involute, thin to moderately thick, usually filiform, soft, abaxial surfaces smooth, adaxial surfaces sparsely scabrous on and between the veins, apices narrowly prow-shaped, flag leaf blades (0.5)1-5 cm. |
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Basal branching | mainly extravaginal. |
mainly intravaginal, some extravaginal. |
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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(7) cm, erect, ovoid, fairly tightly to loosely contracted, congested or moderately congested, with fewer than 50 spikelets; nodes with 1-2 branches; branches 0.5-3 cm, erect to ascending, slightly lax, terete or angled, angles sparsely to densely scabrous, with 2-12 spikelets. |
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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. |
3-6(8) mm, lengths to 3 times widths, laterally compressed, compact, not sexually dimorphic; florets 2-5; rachilla internodes 0.8-1.1 mm, usually not readily visible from the sides, glabrous or sparsely puberulent. |
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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. |
slightly unequal, distinctly keeled, keels smooth or scabrous; lower glumes 2-4 mm, 1-3-veined, about 2/3 the length of the adjacent lemmas; upper glumes 2.9-5 mm; calluses usually diffusely webbed, hairs 1-2 mm, infrequently glabrous; lemmas 2.5-4(4.5) mm, lanceolate, distinctly keeled, moderately to densely finely scabrous, glabrous throughout or the keels and sometimes the marginal veins sparsely puberulent proximally, margins narrowly scarious, glabrous, apices acute; paleas subequal to the lemmas, keels scabrous, intercostal regions glabrous; anthers vestigial (0.1-0.2 mm) or 1.5-2 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. |
= 42. |
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Poa arctica |
Poa confinis |
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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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CA; OR; WA; BC |
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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 confinis grows on sandy beaches and forest margins of the west coast, a habitat that is being lost to invasion by exotic species and development. It is closely related to P. diaboli (see next), from which it differs by a suite of characters. The two species are ecologically and geographically distinct. Poa confinis differs from P. pratensis (p. 522) in having glabrous or sparsely hairy lemmas and diffusely webbed calluses. It is gynodioecious. (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. 552. | ||||||||||||||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Poa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Madropoa > subsect. Madropoa | ||||||||||||||||
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Name authority | R. Br. | Vasey | ||||||||||||||||
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