Poa subg. Arctopoa
Plants perennial; rhizomatous, rhizomes stout, 1.5-3 mm thick, culms mostly solitary. Basal branching extravaginal. Culms (15)20-115 cm tall, 2-3 mm thick, terete or weakly compressed. Sheaths closed for V5-1/3 their length, sometimes fused by a hyaline membrane to 3/4 their length, terete, bases of some basal sheaths densely retrorsely strigose, hairs 0.1-0.2 mm, thick; ligules 1-4(5.5) mm, white to off-white or yellow-cream to brown, truncate to obtuse, ciliolate; blades usually (2)4-11+ mm wide, flat, folded, or involute, thick, abaxial surfaces smooth, margins and sometimes the adaxial veins scabrous, apices narrowly to broadly prow-shaped. Panicles 5-35 cm, erect, contracted to wide open, with (1)2-5 branches per node; branches 1-20 cm, erect to widely spreading, straight or somewhat lax, terete or angled, smooth or scabrous. Spikelets 5-12 mm, laterally compressed, not bulbiferous; florets 2-6(8), bisexual; rachilla internodes smooth or scabrous, glabrous or hairy. Glumes subequal or the lower glumes to 2 mm longer than the upper glumes, outer margins smooth or scabrous, frequently ciliate proximally, distinctly keeled, keels smooth or scabrous; lower glumes 1-3(5) veined; upper glumes (1)3(5) veined; calluses obtusely angled, blunt or weakly pointed, terete, glabrous or with a crown of hairs; lemmas 3.8-7 mm, 5-7-veined, distinctly keeled, membranous to subcoriaceous, glabrous or the keels and marginal veins sparsely hairy on the proximal 1/2, lateral veins faint, intercostal regions smooth or scabrous, margins usually with hairs to 0.2 mm proximally; palea keels scabrous, glabrous or with hairs at midlength, intercostal regions smooth or scabrous, usually glabrous, infrequently puberulent proximally; anthers 3, 1.6-3.2 mm.
Discussion
Poa subg. Arctopoa includes five species in two sections; only one species grows in the Flora region. The species are generally robust, rhizomatous perennials of subsaline or subalkaline soils of wetlands. They have cilia along the lemma and sometimes the glume margins, and the bases of the basal sheaths have short, thick hairs. The subgenus is sometimes treated as a genus. The chloroplast genomes of species in the subgenus are similar to those in Poa sect. Sylvestres; the nuclear ribosomal DNA suggests a relationship with genera outside of Poa, such as Beckmannia (p. 484), Dupontia (p. 602), and Arctophila (p. 605).
Selected References
None.