Poa arctica subsp. arctica

Synonyms: Poa williamsii Poa longipila Poa arctica subsp. williamsii Poa arctica subsp. longiculmis
Treatment appears in FNA Volume 24. Treatment on page 530.
Please click on the illustration for a higher resolution version.
Illustrator: Sandy Long

Copyright: Utah State University

Plants usually loosely, sometimes densely, tufted, rhizomatous, rhizomes short or long, well developed. Ligules (1) 2-4 mm, obtuse to acute; blades 1.5-2.5 (3) mm wide, flat or folded, thin and soon withering, flag leaf-blades 0.7-5.5 cm. Panicles lax to erect, open; branches ascending or widely spreading, sinuous and flexuous to fairly straight, smooth or sparsely scabrous, proximal branches 2/5 – 3/5 the panicle length. Spikelets (3.5) 4.5-6 (7) mm, infrequently bulbiferous; rachilla internodes usually glabrous, infrequently sparsely softly puberulent to long-villous; calluses sparsely to copiously webbed; lemmas (2.7) 3-4.5 mm; palea keels puberulent to long-villous at midlength, intercostal regions usually hairy, sometimes glabrous; anthers usually fully developed, except in the high arctic. 2n = 56, 60, 62, 63, 64, 65, 68, 70, 72, 74, 75, 76, 77, 78, 79, 80, 82, ca. 83, 84, 85, 88, 106.

Discussion

Poa arctica subsp. arctica is polymorphic and circumpolar. It grows in alpine and tundra habitats as far south as Wheeler Peak, New Mexico. Bulbiferous plants are known from alpine habitats in Alaska and British Columbia.

Poa arctica subsp. arctica has tougher leaves, and is less densely hairy between the lemma veins and palea keels, than subsp. aperta. It often grows with subsp. lanata, but can be distinguished by its smaller and, usually, more numerous spikelets and narrower leaves. Paleas that are glabrous between the keels are frequent in plants from the Rocky Mountains. Such plants have been called P. longipila Nash, but do not merit recognition. Hulten (1942) recognized several variants within subsp. arctica; they are of ecotypic significance at best.

Selected References

None.

Lower Taxa

None.

"decumbent" is not a number.

106 +, 88 +, 85 +, 84 +, 83 +, 82 +, 80 +, 79 +, 78 +, 77 +, 76 +, 75 +, 74 +, 72 +, 70 +, 68 +, 65 +, 64 +, 63 +, 62 +, 60 +  and 56 +
membranous +  and scarious +
hairy +, scabrous +  and smooth +
5 cm50 mm <br />0.05 m <br /> (?) +
0.14 cm1.4 mm <br />0.0014 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
scarious-hyaline +
Robert J. Soreng +
R. Br. +
1 (?) +  and 3 (?) +
straight +
basal +  and terminal +
keeled +  and rounded +
strigose +  and glabrous +
not branching +
intravaginal +, extravaginal +, branching +  and basal +
swelling +
not evident +
folded +  and flat +
thin;1.5mm;2.5mm +
flexuous +  and fairly straight +
spreading;ascending +
hispidulous +, glabrous +, smooth or +  and sparsely densely scabrous +
compressed +  and terete +
reduced +  and subequal +
unbranched +  and hollow +
ascending +  and erect +
compressed +  and terete +
slender +  and stout +
7.5 cm75 mm <br />0.075 m <br /> (60 cm600 mm <br />0.6 m <br />) +
not woody +
Mont. +, Wyo. +, Colo. +, N.Mex. +, Wash. +, Utah +, Alaska +, Alta. +, B.C. +, Greenland +, Man. +, Nfld. and Labr. +, N.W.T. +, Nunavut +, Ont. +, Que. +, Sask. +, Yukon +, Idaho +  and Nev. +
1/4 +  and 1/3 +
liquid +, soft +  and hard +
capillary +
pistillate +  and staminate +
sometimes longer +
3 +  and 6 +
compressed +
reduced +
1-3(5)-veined +
shorter or longer +
subtending +
lanceolate +  and broadly lanceolate distinctly or weakly keeled +
subequal +  and unequal +
distributed +
uncinate +
0.02 cm0.2 mm <br />2.0e-4 m <br /> (0.08 cm0.8 mm <br />8.0e-4 m <br />) +
0 +  and 1/6 +
Oval (?) +  and Round (?) +
milky white +  and slightly greenish +
prominent +  and pronounced +
5(7-11)-veined +
hairy +, glabrous +  and chartaceous +
keeled +, lanceolate +  and broadly lanceolate +
0.3 cm3 mm <br />0.003 m <br /> (0.45 cm4.5 mm <br />0.0045 m <br />) +
membranous +
erose +  and entire +
white +  and milky white or hyaline +
obtuse +  and acute +
0.2 cm2 mm <br />0.002 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
membranous +
inconspicuous +
lobed +  and lanceolate +
0.35 cm3.5 mm <br />0.0035 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
concealed +  and prominent +
0 +  and 5 +
2 +  and 1 +
well-developed +
2-keeled +
subequal +
2 cm20 mm <br />0.02 m <br /> (?) +
ovoid +  and broadly pyramidal +
3.5 cm35 mm <br />0.035 m <br /> (15 cm150 mm <br />0.15 m <br />) +
dry +  and fleshy +
1.5 cm15 mm <br />0.015 m <br /> (?) +
infrequently sparsely softly puberulent +  and long-villous +
compressed +
0.45 cm4.5 mm <br />0.0045 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
1 (?) +  and 3 (?) +
simple +  and compound +
2 (?) +  and 3 (?) +
Poa williamsii +, Poa longipila +, Poa arctica subsp. williamsii +  and Poa arctica subsp. longiculmis +
Poa arctica subsp. arctica +
Poa arctica +
subspecies +
membranous +
0.35 cm3.5 mm <br />0.0035 m <br /> (0.55 cm5.5 mm <br />0.0055 m <br />) +
parallel +  and converging +
aquatic +  and terrestrial +