The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

arctic bluegrass

Habit Plants perennial; usually strongly anthocyanic; rhizomatous, rhizomes usually well developed, sometimes poorly developed, shoots usually solitary. Plants annual or perennial; sometimes matlike, sometimes cespitose, sometimes stoloniferous, sometimes 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.

usually hollow, sometimes solid.

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.

Basal branching

mainly extravaginal.

Leaves

distichous;

sheaths usually open to the base, varying to closed for nearly their full length;

auricles present or absent;

abaxial ligules absent;

adaxial ligules scarious or membranous, sometimes puberulent or scabridulous, usually not ciliate, cilia sometimes shorter than the base;

pseudopetioles rarely present;

blades usually linear, sometimes broadly so, venation parallel;

cross sections non-Kranz, mesophyll nonradiate, adaxial palisade layer absent, fusoid and arm cells usually absent;

midribs usually simple;

adaxial bulliform cells present;

stomates with parallel-sided subsidiary cells;

epidermes usually lacking bicellular microhairs, sometimes with unicellular microhairs, papillae usually absent, when present, rarely more than 1 per cell.

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.

Inflorescences

usually terminal, panicles, spikes, or racemes, usually ebracteate;

disarticulation usually below the florets, sometimes below the glumes, at the rachis nodes, or at the inflorescence bases.

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.

usually bisexual, infrequently unisexual or mixed, usually laterally compressed or not compressed, occasionally dorsally compressed, with 1-30 sexual florets, distal floret(s) often reduced, infrequently spikelets with 1-2 reduced or staminate basal florets and a single terminal sexual floret.

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.

usually 2, upper or lower glumes sometimes absent, rarely both glumes absent;

lemmas without uncinate hairs, awned or not, awns single, basal to apical;

paleas usually well-developed, sometimes reduced or absent;

lodicules 2(3), usually lanceolate and broadly membranous distally, rarely truncate and fleshy, usually not veined or obscurely veined, sometimes distinctly veined, sometimes ciliate;

anthers (1, 2)3;

ovaries glabrous or sometimes hairy distally, sometimes with an apical appendage;

haustorial synergids absent;

styles (1)2 (-4), bases close together, sometimes fused.

Caryopses

hila linear, elliptic, ovate, or punctate;

endosperm usually hard, sometimes soft or liquid, with or without lipids, starch grains compound or simple;

embryos less than 1/2 the length of the caryopses;

epiblasts usually present;

scutellar cleft usually absent;

mesocotyl internode usually absent;

embryonic leaf margins overlapping, x = 7, 10.

2n

= 36, 42, 56, 60, 62-68, 70, ca. 72, 74-76, 78-80, 82-84, 86, 88, 99, 106.

Poa arctica

Poaceae subfam. pooideae

Distribution
from FNA
AK; CO; ID; MT; NM; NV; UT; WA; WY; AB; BC; MB; NL; NT; NU; ON; QC; SK; YT; Greenland
[WildflowerSearch map]
[BONAP county map]
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.)

The subfamily Pooideae includes approximately 3300 species, making it the largest subfamily in the Poaceae. It reaches its greatest diversity in cool temperate and boreal regions, extending across the tropics only in high mountains.

The circumscription and relationships of tribes within the Pooideae are unsettled (see, for example, Catalan et al. 1997, 2004; Soreng and Davis 1998). In this flora, some previously recognized tribes have been combined with the Poeae. Recognition of some of these as subtribes is well supported; among these is the Hainardieae Greuter (which, at the subtribal level, is called the Parapholiinae Caro). Members of other traditional tribal groupings, such as the Aveneae Dumort., appear to be widely dispersed within the Poeae sensu lato. Further work will probably support the division of the expanded Poeae into additional tribes; there is as yet no clear indication as to what the boundaries of such tribes should be.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Plants lacking well-developed rhizomes; anthers aborted late in development; plants of the high arctic
subsp. caespitans
1. Plants usually with well-developed rhizomes; anthers normal or plants not of the high arctic.
→ 2
2. Panicles erect, the branches relatively stout, fairly straight; longest branches of the lowest panicle nodes 1/4-1/2 the length of the panicles; culms wiry, usually several together; calluses glabrous or shortly webbed; paleas sometimes glabrous; plants glaucous, growing in the southern Rocky-Mountains and adjacent portions of the Intermountain region
subsp. aperta
2. Panicles lax to erect, the branches slender, flexuous to fairly stout and straight; longest branches of the lowest panicle nodes 2/5 – 3/5 the length of the panicles; culms slender to stout, varying from solitary to several together; calluses glabrous or webbed, the hairs usually more than 1/2 as long as the lemmas; paleas pubescent; plants sometimes glaucous, widespread in distribution.
→ 3
3. Calluses glabrous; spikelets not bulbiferous
subsp. grayana
3. Calluses webbed, often copiously so, sometimes glabrous in bulbiferous spikelets; spikelets sometimes bulbiferous.
→ 4
4. Spikelets (5)6-8 mm long; lemmas 4-6 mm long; blades 2-6 mm wide; rachillas usually hairy; plants primarily of the western arctic, extending to northwestern British Columbia
subsp. lanata
4. Spikelets (3.5)4-7 mm long; lemmas (2.7)3-4.5 mm long; blades 1.5-3 mm wide; rachillas commonly glabrous; plants widespread
subsp. arctica
1. Inflorescences 1-sided spikes, the spikelets radial to and partially embedded in the rachises; spikelets with 1 floret each
Nardeae
1. Inflorescences panicles, racemes, or 2-sided spikes with spikelets radial or tangential to the rachises, sometimes embedded in the axes, never both radial and embedded; spikelets with 1-30 florets.
→ 2
2. Cauline leaf sheaths closed for at least 3/4 their length; lemmas longer than (4.5)6.5 mm or awned or with prominent, parallel veins.
→ 3
3. Ovary apices glabrous; styles fused at the base, divergent, naked on the lower portion, plumose distally; lemmas often with a purplish band in the distal 1/2, usually unawned; distal 1-3 florets often reduced to lemmas, the lower 1-2 lemmas often enclosing the terminal lemmas; lodicules about 0.2-0.5 mm long, truncate, fleshy, without a distal membranous portion
Meliceae
3. Ovary apices hairy; styles separate and plumose to the base; lemmas usually without a purplish band, sometimes with purplish bases, usually awned; distal 1-2 florets sometimes reduced, each separate with lemma and palea; lodicules usually more than 1 mm long, fleshy at the base, with a distal membranous portion
Bromeae
2. Cauline leaf sheaths usually open for most or all of their length; if the sheaths closed, the lemmas shorter than 7 mm, unawned and with lemma veins inconspicuous and converging distally.
→ 4
4. Inflorescences usually spikes or spikelike racemes, sometimes panicles, lateral spikelets on pedicels less than 3 mm long; if inflorescences with 1 spikelet per node, the spikelets tangential to the rachises or pedicellate and the lemmas unawned or terminally awned; ovary apices hairy.
→ 5
5. Glumes unequal, exceeded by the lowest lemmas, lanceolate, apices obtuse to acuminate or mucronate, rarely awned; inflorescences spikelike racemes, all spikelets pedicellate; pedicels 0.5-2.5 mm long
Brachypodieae
5. Glumes equal to unequal, sometimes absent, frequently exceeding the lowest lemmas, subulate to lanceolate, ovate, or obovate, apices truncate to acuminate, frequently awned; inflorescences usually spikes or spikelike, with 1 or more sessile spikelets per node, sometimes a panicle; pedicels absent or up to 4 mm long
Triticeae
4. Inflorescences usually panicles, sometimes racemes with pedicels more than 2.5 mm long, or spikes with 1 spikelet per node and the spikelets radial or tangential to the rachises; if spikelets 1 per node and tangential, the lemmas awned from midlength to subapically, never terminally, if spikes with radial spikelets, the lemmas unawned or awned, awns basal to terminal; ovary apices usually glabrous, sometimes hairy.
→ 6
6. Lower glumes absent or highly reduced; inflorescences panicles
Brachyelytreae
6. Lower glumes usually well-developed, sometimes present only on the terminal spikelets; inflorescences panicles, racemes, or spikes.
→ 7
7. Caryopses beaked; blades tapering both basally and apically, midveins usually eccentric
Diarrheneae
7. Caryopses not beaked; blades usually tapering only apically, midveins usually centric.
→ 8
8. Spikelets with 1 floret; lemmas terminally awned, the junction of the lemma and awn abrupt, evident; glumes equal to or longer than the florets
Stipeae
8. Spikelets with 1-22 florets; lemmas unawned or dorsally to terminally awned, if terminally awned, the transition from lemma to awn gradual, not evident; glumes absent or shorter than to longer than the adjacent florets.
→ 9
9. Lemmas membranous, bidentate or bifid; both surfaces of the leaf blades deeply ribbed; ovary apices hairy; culms with solid internodes; plants cultivated or established at a few locations
Stipeae
9. Lemmas hyaline to membranous, entire or minutely bidentate; leaf blades rarely deeply ribbed on both sides; ovary apices usually glabrous; culms usually with hollow internodes; plants mostly native or established throughout the Flora region, sometimes cultivated
Poeae
Source FNA vol. 24. FNA vol. 24, p. 57. Author: Grass Phylogeny Working Group;.
Parent taxa Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Poa Poaceae
Sibling taxa
P. abbreviata, P. alpina, P. alsodes, P. ammophila, P. annua, P. arachnifera, P. arida, P. arnowiae, P. atropurpurea, P. autumnalis, P. bigelovii, P. bolanderi, P. bulbosa, P. chaixii, P. chambersii, P. chapmaniana, P. compressa, P. confinis, P. curtifolia, P. cusickii, P. cuspidata, P. diaboli, P. douglasii, P. eminens, P. fendleriana, P. glauca, P. hartzii, P. howellii, P. infirma, P. interior, P. keckii, P. kelloggii, P. laxa, P. laxa × glauca, P. laxiflora, P. leibergii, P. leptocoma, P. lettermanii, P. macrantha, P. macrocalyx, P. marcida, P. napensis, P. nemoralis, P. nervosa, P. occidentalis, P. paludigena, P. palustris, P. paucispicula, P. piperi, P. porsildii, P. pratensis, P. pringlei, P. pseudoabbreviata, P. reflexa, P. rhizomata, P. saltuensis, P. secunda, P. sierrae, P. stebbinsii, P. stenantha, P. strictiramea, P. sublanata, P. suksdorfii, P. supina, P. sylvestris, P. tenerrima, P. tracyi, P. trivialis, P. unilateralis, P. wheeleri, P. wolfii, P. ×gaspensis, P. ×limosa, P. ×nematophylla
Subordinate taxa
P. arctica subsp. aperta, P. arctica subsp. arctica, P. arctica subsp. caespitans, P. arctica subsp. grayana, P. arctica subsp. lanata
Name authority R. Br. Benth.
Web links