Poa cuspidata |
Poa laxa |
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early bluegrass |
banff bluegrass, glaucous bluegrass, lax bluegrass, Mt. Washington bluegrass, wavy blue grass |
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Habit | Plants perennial; loosely tufted or with solitary shoots, shortly rhizomatous. | Plants perennial; not or only slightly glaucous; densely tufted, not stoloniferous, not rhizomatous. | ||||
Culms | 15-60 cm, erect or the bases decumbent, not branching above the base, terete or weakly compressed; nodes terete, 0-1 exserted. |
8-35 cm tall, 0.5-0.9 mm thick, ascending to erect, slender; nodes terete, 0(1) exserted. |
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Sheaths | closed for about 1/2 their length, slightly compressed, distinctly keeled, glabrous, bases of basal sheaths glabrous, distal sheath lengths 4-60 times blade lengths; collars of proximal leaves usually retrorsely scabrous or pubescent distally and about the throat; ligules 0.5-4 mm, smooth or scabrous, apices truncate to acute; innovation blades similar to the cauline blades; cauline blades 1-4 mm wide, usually flat, sometimes slightly folded, smooth or sparsely scabrous, primarily over the veins, apices broadly prow-shaped, blades steeply reduced in length distally, flag leaf blades 0.2-3(6) cm. |
closed for 1/5-1/3 their length, terete, smooth, glabrous, bases of basal sheaths glabrous; collars smooth or scabrous, glabrous; ligules 2-4 mm, smooth, apices acute, often lacerate; innovation blades similar to the cauline blades; cauline blades 1-2(3) mm wide, flat, thin, soft, smooth, narrowly prow-tipped, blades not strongly graduated or reduced upwards. |
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Basal branching | mainly extravaginal. |
mixed, mainly extravaginal or mainly pseudointravaginal, sometimes intravaginal. |
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Panicles | 5-15 cm, erect or lax, pyramidal, open, sparse, with 20-80 spikelets, proximal internodes usually 3+ cm; nodes usually with 2 branches; branches (2)3-7(10) cm, spreading to reflexed, straight, angled, angles scabrous, with 2-8(10) spikelets. |
2-8 cm, slightly lax, usually loosely contracted and sparse, infrequently contracted and dense; nodes with 1-3(5) branches; branches 1-3(4) cm, usually ascending or weakly spreading, infrequently erect, fairly straight or flexuous, slender, sulcate or angled, smooth or the angles sparsely scabrous, with 1-8 spikelets. |
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Spikelets | 5-8 mm, lengths to 3.5 times widths, laterally compressed, not sexually dimorphic; florets 2-5; rachilla internodes smooth. |
4-6 mm, lengths to 3 times widths, laterally compressed; florets 2-5; rachilla internodes shorter than 1 mm, smooth, glabrous. |
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Glumes | narrowly lanceolate to lanceolate, distinctly keeled; lower glumes 1-3-veined; calluses webbed, hairs over 1/3 the lemma length; lemmas 3-6 mm, lanceolate, distinctly keeled, keels and marginal veins sparsely short- to long-villous, lateral veins moderately prominent, intercostal regions glabrous or the upper florets in the spikelets softly puberulent, margins glabrous, apices acute; palea keels scabrous, softly puberulent at midlength; anthers vestigial (0.1-0.2 mm) or 2-3.5 mm. |
nearly equaling or slightly longer than the adjacent lemmas, lanceolate to broadly lanceolate, thin, distinctly keeled, keels smooth or sparsely scabrous; lower glumes 1-3-veined; upper glumes shorter than or subequal to the lowest lemmas; calluses glabrous or webbed, hairs usually shorter than 1/4 the lemma length, sparse; lemmas 3-4.6 mm, lanceolate to broadly lanceolate, thin, distinctly keeled, keels and marginal veins short- to long-villous, lateral veins glabrous or sparsely softly puberulent, lateral veins obscure, intercostal regions glabrous, margins glabrous, apices acute; paleas sparsely scabrous over the keels; anthers (0.6)0.8-1.1(1.3) mm. |
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2n | = 28. |
= 28, 42, 84. |
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Poa cuspidata |
Poa laxa |
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Distribution |
AL; DC; DE; GA; IN; KY; LA; MD; NC; NJ; NY; OH; PA; SC; TN; VA; WV
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CO; ME; MT; NH; NY; OR; VT; WY; AB; BC; NL; QC |
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Discussion | Poa cuspidata is a common species of forest openings in the Appalachian Mountains. It is an eastern counterpart of P. arnowiae (see previous), P. tracyi (p. 543), and P. nervosa (see next). Like those species, it is sequentially gynomonoecious. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Poa laxa is a low arctic to high alpine amphiatlantic species. It has been treated as a series of separate species, but the differences seem relatively minor and incomplete. Its short anthers and smoother branches usually distinguish it from P. glauca (p. 576), with which it can hybridize to form P. laxa x glauca (p. 572). Poa laxa has four subspecies, two of which are native to the Flora region; subsp. laxa grows in central Europe; and subsp. flexuosa (Sm.) Hyl. in northwestern Europe. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 24, p. 545. | FNA vol. 24, p. 570. | ||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Madropoa > subsect. Poa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Oreinos | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Name authority | Nutt. | Haenke | ||||
Web links |