POA L. Bluegrass
Plants dioecious or hermaphroditic, caespitose or stoloniferous or rhizomatous, annual or perennial. Culms erect or
ascending or decumbent, glabrous; internodes hollow, terete (except flat in P. compressa). Leaves mostly basal, not distichous;
sheaths terete, margins partially connate; auricles absent; ligules membranous; blades flat or folded or
involute (upper surface with two median lines and apex frequently keeled), lax. Panicles open or
narrow or contracted, primary branches spreading or ascending or appressed. Spikelets solitary, laterally compressed
, disarticulation above glumes, awnless, pedicellate; florets 2-9, reduced floret at apex, callus hairy
or glabrous; glumes 2, the first 1-3-veined the second 3-veined, slightly unequal, shorter than first floret
, usually glabrous, awnless; lemmas 5-veined (veins converging), membranous (anthocyanous near middle),
glabrous or scabrous or cobwebby hairs, apex broadly acute to obtuse, awnless, veins glabrous or scabrous or
pilose; paleas 2-veined, awnless, ciliate. Stamens 3; anthers yellow. Caryopses laterally compressed or dorsally compressed.
Base chromosome number x=7.
A variable genus of about 500 species worldwide. This genus is adapted to cool temperate or arctic
regions where it is an ecological dominant in grasslands and meadows. The total variation of the species along with
the apomictic reproductive behavior of several species makes this a taxonomically difficult genus.