Poa arida
Poa paucispicula
plains bluegrass, prairie speargrass
Alaska blue grass, few-flower bluegrass
15-80 cm, erect or the bases decumbent, terete or weakly compressed;
nodes terete, 0-1 exserted.
10-30 cm.
closed for 1/10 – 1/5(1/4) their length, terete, smooth or sparsely scabrous, glabrous, bases of basal sheaths glabrous, distal sheath lengths (1.2)1.5-9(20) times blade lengths;
ligules (1)1.5-4(5) mm, smooth or sparsely to moderately scabrous, apices obtuse to acute;
blades strongly to gradually reduced in length distally, 1.5-5 mm wide, flat and moderately thin to folded and moderately thick and firm, abaxial surfaces smooth, adaxial surfaces smooth or sparsely to moderately scabrous, primarily over the veins, apices narrowly prow-shaped, flag leaf blades (0.4)1-7(10) cm.
closed for 1/4 - 3/5 their length, terete;
ligules 1-2 mm, smooth or sparsely scabrous, truncate to obtuse;
blades 1-3 mm wide, flat, thin, soft, apices broadly prow-shaped.
intra- and extravaginal.
mainly extravaginal.
(2.5)4-12(18) cm, erect, usually narrowly lanceoloid, contracted, sometimes interrupted, infrequently loosely contracted, usually congested, with 25-100 spikelets;
nodes with 1-5 branches;
branches 1-9 cm, erect to infrequently ascending, rarely spreading, terete to weakly angled, smooth or the angles sparsely to moderately scabrous, with 3-24 spikelets.
2.5-10 cm, lax to nearly erect, open, sparse, with 1-2 branches per node;
branches (2)3-6 cm, ascending to spreading, lower branches infrequently reflexed, lax or drooping, capillary, terete to slightly sulcate, usually smooth, rarely some branches within a panicle sparsely scabrous, with 1-3(5) spikelets.
3.2-7 mm, lengths to 3.5(3.8) times widths, laterally compressed;
florets 2-7;
rachilla internodes smooth, sometimes sparsely puberulent.
4-6 mm, laterally compressed, broadly lanceolate to ovate, usually dark purple, with 3-5 florets;
rachilla internodes smooth, glabrous.
lanceolate, distinctly keeled, smooth or sparsely scabrous;
lower glumes 3-veined;
calluses usually glabrous, infrequently webbed, hairs to 1/4 the lemma length;
lemmas 2.5-4.5 mm, lanceolate to narrowly lanceolate, distinctly to weakly keeled, keels and marginal veins short- to long-villous, lateral veins moderately prominent, glabrous or puberulent, intercostal regions usually glabrous, infrequently hairy, hairs to 0.3 mm, margins glabrous, apices acute or blunt;
palea keels scabrous, glabrous or short-villous at midlength, intercostal regions usually glabrous, sometimes puberulent to short-villous;
anthers 1.3-2.2 mm.
lanceolate to broadly lanceolate, thin, distinctly keeled, keels smooth or nearly so;
lower glumes 1-veined;
upper glumes shorter than or subequal to the lowest lemmas;
calluses sparsely webbed;
lemmas 3-4 mm, broadly lanceolate, usually strongly purple, distinctly keeled, thin, keels and marginal veins short- to long-villous, keels hairy for 1/2-1/3 their length, lateral veins glabrous, intercostal regions smooth, glabrous, margins glabrous, not infolded, apices acute, sometimes slightly bronze-colored;
palea keels sparsely scabrous at midlength;
anthers 0.4-1 mm.
= 56, 56+1, 56-58, 63, 64, 70, 76, 84, ca. 90, 95+-5, 100, 103.
= 28, 42.
Poa arida
Poa paucispicula
Poa arida grows mainly on the eastern slope of the Rocky Mountains and in the northern Great Plains, primarily in riparian habitats of varying salinity or alkalinity. It is spreading eastward along heavily salted highway corridors. Reports of its occurrence west of the Continental Divide and in southwestern Texas are mostly attributable to misidentifications of P. arctica subsp. aperta (p. 530). P. arctica subsp. grayana (p. 532), and rhizomatous specimens of P. fendleriana (p. 556).
Poa arida may reflect past hybridization between P. secunda (p. 586) and a species of Poa sect. Poa. Poa glaucifolia Scribn. & T.A. Williams refers to specimens of the northern Great Plains that have a more lax growth form with broader leaves and occasionally somewhat open panicles, florets with a small web, and sometimes lacking hairs between the keel and marginal veins of the lemma. Plants with these characteristics have chromosome counts of 2ra = 56 and 70, whereas P. arida sensu stricto usually has 2n = 63, 64, or greater than 70. It is suspected that some of the variability reflects introgression from P. secunda.
Poa arida is a named intersectional hybrid
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Poa paucispicula grows in arctic and alpine regions, from the north coast of Alaska and the western Northwest Territories south to Washington, Idaho, and Wyoming; it also grows in arctic far east Russia. It is a delicate species that prefers open, mesic, rocky slopes. It has sometimes been included in P. leptocoma (p. 573), a member of Poa sect. Oreinos. It differs from P. leptocoma in having smoother branches, fewer spikelets, and broader glumes. Chloroplast DNA studies confirm that it is not closely related to species of sect. Oreinos; ITS data support its relationship to P. leptocoma.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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