Poa sect. Dioicopoa
Plants perennial; usually rhizomatous, sometimes tufted or with solitary shoots. Basal branching intra- and extravaginal. Culms 20-85 cm, terete or weakly compressed. Sheaths closed firmly for 1/7 -1/3 their length, sometimes for a longer distance by a hyaline membrane, terete; ligules 1-4 mm (North America); innovation blades sparsely to densely scabrous, mainly over the veins; cauline blades flat or folded, rarely involute, abaxial and adaxial surfaces smooth or sparsely finely scabrous, glabrous, apices narrowly to broadly prow-shaped. Panicles 3-12(18) cm (North America), contracted or infrequently open, congested, branches erect to slightly ascending. Spikelets laterally compressed, sexually dimorphic, not bulbiferous (North America), of different sexes, slightly differentiated in floret number and lemma length, and sharply differentiated in vestiture development; florets normal. Glumes shorter than the adjacent lemmas, distinctly keeled, keels scabrous; lower glumes 1-3-veined; calluses terete or slightly laterally compressed, those of staminate plants often glabrous, those of pistillate plants usually copiously pubescent, hairs arising as a single dorsal tuft and as single tufts from below the marginal veins, long-plicate or rarely closely crimped hairs or a crown of long hairs (in South America); lemmas distinctly keeled, those of pistillate plants pubescent (North America), usually the keels and marginal veins long-villous; paleas scabrous, glabrous, or medially softly puberulent to long-villous over the keels; anthers 3, vestigial (0.1-0.2 mm) or 1.6-2.7 mm.
Discussion
Poa sect. Dioicopoa includes 29 species; all except the North American P. arachnifera are native to South America. The above description applies to the North American species. They are strictly dioecious. All appear to reproduce sexually; a few species are also bulbiferous. Many, including P. arachnifera, are characterized by having 3 well-developed webs on the calluses of the pistillate florets.
Selected References
None.