Mary E. Barkworth FNA 24: 378-388

 Plants annual or perennial; cespitose, rhizomatous, or stoloniferous. Culms annual, not woody, not branching above the base; internodes usually hollow. Sheaths usually open for most of their length, sometimes closed; collars without tufts of hair on the sides; auricles usually absent; ligules membranous to hyaline, sometimes ciliate, those of the upper and lower cauline leaves usually similar; pseudopetioles not developed; blades linear to narrowly lanceolate, venation parallel, cross venation not evident, without arm or fusoid cells, epidermes without microhairs, not papillate, cross sections non-Kranz. Inflorescences terminal, usually panicles, sometimes spikes, panicles sometimes spikelike or reduced to racemes in depauperate specimens; disarticulation usually above the glumes and beneath the florets, sometimes below the glumes. Spikelets 0.7–50 mm, laterally compressed, sometimes weakly so, sometimes viviparous, usually with 2–22 florets, sometimes with 1, the non-reproductive florets usually distal to the reproductively functional florets, sometimes with 1 or 2 staminate or sterile florets below the functional floret(s), the non-reproductive florets often reduced in size, sometimes to lemmas; rachillas sometimes prolonged beyond the base of the distal florets. Glumes (1)2, equal or unequal, shorter or longer than the adjacent florets, sometimes exceeding the distal florets; florets laterally compressed; calluses glabrous or hairy, not well developed; lemmas lanceolate to ovate, 1–7(9)-veined, unawned or awned, veins usually converging distally, sometimes parallel, awns from basal to terminal on the lemmas, straight or bent; paleas 2-keeled, from shorter to longer than the lemmas, sometimes absent or minute; lodicules 2, membranous, not or weakly veined; anthers 3; ovaries usually glabrous, sometimes hairy distally; styles 2, bases free. Caryopses longitudinally grooved or not, not beaked, pericarp thin; hila punctate to linear; embryos from 1/4–1/3 as long as the caryopses. x = 7. 

The Poeae constitute the largest tribe of grasses, encompassing around 115 genera and 2500 species. The species are primarily cool-temperate to arctic in their distribution. In North America north of Mexio, there are 63 non-hybrid genera with 344 species and 4 hybrid genera, each of which as one species. Many of the tribe’s species are well known as lawn and pasture grasses, for example, Poa pratensis (Kentucky bluegrass), Dactylis glomerata (orchard grass), and Phleum pratense (Timothy).

The tribe’s circumscription and its infratribal taxonomy are unclear. It is interpreted here as including generic groups that are, or have been, treated in other works as tribes (e.g., Agrostideae Dumort., Aveneae Dumort., Hainardeae Greut., and Phalarideae Dumort.). Some of these have been recognized as subtribes but OpenHerbarium does not include include subtribes in its classification. Recent studies (e.g., Catalán et al. 1997, 2004; Soreng and Davis 1998) indicate that there are some infratribal groupings that, based on chloroplast DNA data, appear stable; other groupings do not.

The circumscription of some pooid genera in OpenHerbarium differs from that adopted in Flora of North America. Reasons are included in the appropropiate generic descriptions. Some of the genera recognized are not monophylletic. Polyploidy can result in evolution of species groups that have distinctive morphological and ecological trajectories. Including all such groups in a single genus tends to hide valuable information. 

The keys usually do not include the hybrid genera. There are fourin North America:  × Agropogon (Agrostis × Polypogon), ×Arctodupontia (Arctophila × Dupontia), ×Dupoa (Dupontia × Poa), and ×Pucciphippsia (Puccinellia × Phippsia). They are described and illustrated.

Links to key for the Poeae in North America north of Mexico, Pakistan, Somaliland and Somalia. 

SELECTED REFERENCES (not updated since 2007).

Catalán, P., E.A. Kellogg, and R.G. Olmstead. 1997. Phylogeny of Poaceae subfamily Poöideae based on chloroplast ndhF gene sequences. Molec. Phylogenet. Evol. 8:150–166.

Calalán, P., P. Torrecilla, J.Á. López Rodríguez, and R.G. Olmsted. 2004. Phylogeny of the festucoid grasses of subtribe Loliinae and allies (Poeae, Poöideae) inferred from ITS and trnL–F sequences. Molec. Phylogenet. Evol. 31:517–541.

Macfarlane, T.D. 1987. Poaceae subfamily Poöideae. Pp. 265–276 in T.R. Soderstrom, K.W. Hilu, C.S. Campbell and M.E. Barkworth (eds.). Grass Systematics and Evolution. Smithsonian Institution Press, Washington, D.C., U.S.A. 473 pp.

Soreng, R.J. and J.I. Davis. 1998. Phylogenetics and Character Evolution in the Grass Family (Poaceae): Simultaneous Analysis of Morphological and Chloroplast DNA Restriction Site Character Sets. Bot. Rev. 64: 1–85.

Soreng, R.J., J.I. Davis, and J.J. Doyle. 1990. A phylogenetic analysis of chloroplast DNA restriction site variation in Poaceae subfam. Poöideae. Pl. Sys.