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, sterile florets usually distal to the reproductively functional florets, sometimes with 1 or 2 staminate or sterile florets below a bisexual floret, sterile florets often reduced in size; rachillas sometimes prolonged beyond the base of the distal florets. Glumes (0,1)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 than 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.

Discussion

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 the Flora region, there are 63 non-hybrid genera with 344 species, and 4 hybrid genera, each of which has 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 are sometimes recognized as subtribes, often with modified circumscriptions. Recent studies (e.g., Catalan 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. In addition, there is little support for the monophyly of some genera, notably Festuca and its allies.

The following key does not include these four hybrid genera: xAgropogon (Agrostis x Polypogon, p. 668), xArctodupontia (Arctopbila x Dupontia, p. 604), xDupoa (Dupontia x Poa, p. 601), and ×Pucciphippsia (Puccinellia x Phippsia, p. 477). They are described on the pages indicated. In the key that follows, branch measurements include spikelets, but not awns.

Keys

1 All or almost all spikelets viviparous, the spikelets producing plantlets [if sexual spikelets are common, take the alternate lead]. > 2
2 Panicle branches smooth or slightly scabrous, the scabrules widely spaced; blades with a translucent line on either side of the midvein, apices usually prowlike Poa
2 Panicle branches scabrous; blades without a translucent line on either side of the midvein, apices usually not prowlike. > 3
3 Sheaths closed for 1/2 or more of their length; ligules 0.1-0.6 mm long Festuca
3 Sheaths open; ligules 1.5-13 mm long Deschampsia
1 Some, usually all, spikelets sexually functional, with 1-25 bisexual or unisexual florets, sometimes with sterile and sexual spikelets mixed within an inflorescence. > 2
4 Inflorescences with 2 morphologically distinct forms of spikelets. > 5
5 Spikelets in pairs, the pedicels not fused at the base, smooth or slightly scabrous; disarticulation above the glumes and beneath the florets Cynosurus
5 Spikelets in fascicles, the pedicels fused at the base, glabrous, hispid or strigose; disarticulation at the base of the fused pedicels. > 6
6 Secondary panicle branches sharply bent below the pedicels; glumes not winged Lamarckia
6 Secondary panicle branches straight below the pedicels; glumes winged Phalaris
4 Inflorescences with all spikelets morphologically alike. > 5
7 Glumes with pilose awns Lagurus
7 Glumes, if present, unawned or with glabrous awns. > 8
8 Inflorescences spikes with 1-2(4) spikelets per node, or spikelike racemes with 1 spikelet at all or most nodes. > 9
9 Spikelets with 1 functional floret, sometimes a reduced, sterile floret also present. > 10
10 Glumes membranous, flexible; all spikelets pedicellate, pedicels 0.5-1 mm long, 0.1-0.2 mm thick Mibora
10 Glumes coriaceous, stiff; lower spikelets sessile, upper spikelets sometimes pedicellate. > 11
11 Spikelets radial to the rachises, most spikelets with 1 glume, the terminal spikelets with 2 glumes Hainardia
11 Spikelets tangential to the rachises, all with 2 glumes. > 12
12 Lemmas unawned Parapholis
12 Lemmas awned, awns 2-4 mm Scribneria
9 Spikelets with 2-25 functional florets. > 10
13 Lemmas awned from about midlength, awns 8-26 mm long, twisted proximally. > 14
14 Adaxial surfaces of the leaves ribbed; rachillas pilose on all sides; ligules truncate to rounded, 0.5-1.5 mm long Helictotrichon
14 Adaxial surfaces of the leaves unribbed; rachillas glabrous on the side adjacent to the paleas, hairy elsewhere; ligules acute to truncate, 0.5-7 mm long Avenula
13 Lemmas unawned or apically awned, awns straight. > 14
15 Spikelets sessile; lemmas 2-12 mm long. > 16
16 Spikelets radial to the rachises, most spikelets with 1 glume, only the terminal spikelet with 2 glumes Lolium
16 Spikelets tangential to the rachises, all spikelets with 2 glumes Gaudinia
15 Spikelets subsessile to pedicellate, pedicels 0.5-3 mm long. > 16
17 Plants perennial Festuca
17 Plants annual. > 18
18 Inflorescences usually exceeded by the leaves; spikelets with (2)3-4(7) florets; lemmas (5)7-9-veined, apices round to emarginate, not bifid; culms usually prostrate or procumbent Sclerochloa
18 Inflorescences usually exceeding the leaves; spikelets with 4-25 florets; lemmas 5-veined, apices acute to obtuse, sometimes bifid; culms procumbent to erect Desmazeria
8 Inflorescences panicles or racemes, with more than 1 spikelet associated with each node. > 9
19 Inflorescences racemes or spikelike panicles, with all branches shorter than 1 cm [for opposite lead, see p. 382]. > 20
20 Leaves usually exceeding the inflorescences; culms usually prostrate to procumbent; lemmas indurate at maturity Sclerochloa
20 Leaves usually exceeded by the inflorescences; culms usually erect or decumbent at the base; lemmas usually membranous or papery, sometimes coriaceous, not indurate. > 21
21 Spikelets disarticulating below the glumes or, if the spikelets are attached to stipes, at the base of the stipes; glume bases sometimes fused. > 22
22 Spikelets weakly laterally compressed, with stipes that fall with the spikelets; glume bases not fused; glumes usually awned Polypogon
22 Spikelets strongly laterally compressed, without stipes; glume bases sometimes fused; glumes unawned or awned. 23. Lemmas dorsally awned; spikelets oval in outline; glumes often connate at the base, often winged distally, keels sometimes ciliate, apices never abruptly truncate Alopecurus
23 Lemmas usually unawned, occasionally subterminally awned; spikelets often U-shaped in outline, sometimes oval; glumes not connate at the base, not winged, often strongly ciliate on the keels and abruptly truncate to an awnlike apex Phleum
21 Spikelets disarticulating above the glumes; glume bases not fused. > 22
24 Spikelets with 2-25 bisexual florets, the sterile or staminate florets, if present, distal to the bisexual florets. > 25
25 Sheaths closed for at least 1/2 their length. > 26
26 Lemma midveins sometimes excurrent up to 2.2 mm, other veins not excurrent; plants native, arctic Dupontia
26 Lemmas with 3-5 veins excurrent, forming awnlike teeth; plants cultivated Sesleria
25 Sheaths open for all or almost all of their length. > 26
27 Distal lemmas, sometimes all lemmas, awned from below midlength Aira
27 All lemmas unawned or apically awned. > 28
28 Lemmas coriaceous at maturity, unawned, sometimes mucronate Desmazeria
28 Lemmas membranous, apically awned, awns 0.3-22 mm long. > 29
29 Lemma margins involute, not scarious Vulpia
29 Lemma margins flat, scarious Rostraria
24 Spikelets with 1 bisexual floret, sometimes with 1-2 sterile florets below the bisexual floret, the sterile florets sometimes reduced to lemmas, sometimes resembling tufts of callus hair. > 25
30 Spikelets with 1-2 sterile or staminate florets below the bisexual florets, these from larger than to much smaller than the bisexual florets, sometimes resembling tufts of hair; glumes sometimes winged distally. > 31
31 Fresh leaves not sweet-smelling when crushed; sterile lemmas unawned; bisexual lemmas usually hairy, sometimes sparsely so; glumes subequal, sometimes winged distally Phalaris
31 Fresh leaves sweet-smelling when crushed; sterile lemmas awned; bisexual lemmas glabrous; glumes unequal, not winged Anthoxanthum
30 Spikelets without sterile or staminate florets below the bisexual floret; glumes not winged distally. > 31
32 Lemmas dorsally awned, awns geniculate; lateral lemma veins excurrent, forming 4 teeth, teeth sometimes awnlike Bromidium
32 Lemmas unawned or with only 1 awn, awns not strongly geniculate; lateral lemma veins not excurrent. > 33
33 Spikelets 8-15 mm long; lemmas more than 3/4 as long as the glumes; plants strongly rhizomatous Ammophila
33 Spikelets 1.2-7 mm long; lemmas less than 3/4 as long as the glumes; plants rhizomatous or not. > 34
34 Sheaths closed for at least 1/2 their length. > 35
35 Calluses glabrous; exposed at maturity; lemmas 1-3-veined, unawned; [other genera may develop long caryopses when infected by nematodes or fungi; such caryopses are usually deformed and filled with eggs, larvae, or spores] Phippsia
35 Calluses with a ring of stiff hairs, hairs to about 1 mm long; lemmas 3-11-veined Dupontia
34 Sheaths open for most of their length. > 35
36 Spikelet bases usually U-shaped, sometimes cuneate; glumes equal, midveins usually strongly ciliate Phleum
36 Spikelet bases cuneate; glumes unequal, midveins not strongly ciliate. > 37
37 Both glumes twice as long as the lemmas; lemmas pubescent Gastridium
37 Glumes from slightly shorter than to slightly longer than the lemmas; lemmas glabrous, sometimes scabridulous or scabrous. > 38
38 Lemma awns 4-16 mm long; plants annual; paleas from 3/4 as long as to slightly longer than the lemmas Apera
38 Lemma awns to 10 mm, if longer than 4 mm, plants perennial and/or paleas less than 1/2 as long as the lemmas Agrostis
19 Inflorescences panicles, dense to open, sometimes compact, usually at least some branches longer than 1 cm [for opposite lead, see p. 380]. > 20
39 Caryopses usually as long as or longer than the lemmas, exposed at maturity; lemmas 1-3-veined, unawned; spikelets with 1 floret; sheaths of the flag leaves closed for at least 1/2 their length; calluses glabrous [other genera may develop long caryopses when infected by nematodes or fungi; such caryopses are usually deformed or filled with eggs, larvae, or spores]. > 40
40 Lemmas 1-veined, narrowed to awnlike apices; sheaths strongly inflated; glumes absent; plants of temperate habitats Coleanthus
40 Lemmas 1-3-veined, apices acute to rounded; sheaths not inflated; glumes developed, caducous or persistent; plants of arctic or alpine Phippsia
39 Caryopses shorter than the lemmas, concealed at maturity; lemmas 3-11-veined; spikelets with 1 or more florets; leaf sheaths open or closed; calluses glabrous or with hairs. > 40
41 Panicle branches secund, appearing 1-sided; spikelets strongly imbricate, subsessile. > 42
42 Culms usually prostrate or procumbent; glumes obtuse to emarginate Sclerochloa
42 Culms erect or ascending; glumes apiculate to awn-tipped. > 43
43 Lemmas awned, awns of the lowest lemmas 0.3-22 mm long Vulpia
43 Lemmas unawned, sometimes awn-tipped. > 44
44 Spikelets circular to ovate or obovate in outline, with 1-2 florets; glumes almost entirely concealing the sides of the florets; disarticulation below the glumes Beckmannia
44 Spikelets oval in outline, longer than wide, with 2-6 florets; glumes partially exposing the sides of the florets; disarticulation above the glumes Dactylis
41 Panicle branches not secund; spikelets usually widely spaced to somewhat imbricate, usually clearly pedicellate, sometimes subsessile, sometimes on stipes. > 42
45 All or most spikelets in an inflorescence with 1 bisexual floret, sometimes with 1-2 sterile or staminate florets below the bisexual floret, the sterile florets sometimes resembling tufts of hair Subkey I
45 All or most spikelets in an inflorescence with 2-25 sexual florets, usually all florets bisexual or the distal florets sterile or unisexual, sometimes all florets unisexual, sometimes the plants unisexual Subkey II

POEAE SUBKEY I

1 Spikelets with 1-2 staminate or sterile florets below the bisexual floret, sterile florets sometimes knoblike or resembling tufts of hair. > 2
2 Spikelets with 2 florets of similar size, the lower floret staminate; lower lemmas awned, the lemmas of the terminal floret unawned or awned Arrhenatherum
2 Spikelets with 2-3(4) florets, the lower 1-2 florets staminate or sterile, sometimes knoblike or resembling tufts of hair, sometimes larger than the bisexual floret; lemmas of the lower florets awned or unawned, the lemmas of the terminal floret unawned. > 3
3 Lower sterile florets 2, from shorter than to exceeding the bisexual floret; fresh leaves sweet-smelling when crushed Anthoxanthum
3 Lower sterile florets 1-2, varying from knoblike projections on the callus of the bisexual floret to linear or lanceolate lemmas up to 3/4 as long as the bisexual floret; fresh leaves not sweet-smelling when crushed Phalaris
1 Spikelets without staminate or sterile florets below the bisexual florets. > 2
4 Spikelets 15-50 mm long; lemmas usually dorsally awned, awns 20-90 mm long, sometimes unawned Avena
4 Spikelets 1-15 mm long; lemmas unawned or awned, awns to 18 mm long, basal, dorsal, subterminal, or terminal. > 5
5 Glume bases gibbous and subcoriaceous; disarticulation above the glumes Gastridium
5 Glumes bases not gibbous, usually membranous; disarticulation above or below the glumes. > 6
6 Lemmas awned, awns longer than 2 mm. > 7
7 Glumes coriaceous, rigid, hispid or scabrous; lemmas awned, awns 5-14.5 mm long, subterminal Limnodea
7 Glumes membranous, flexible, glabrous or with soft hairs, usually smooth; lemmas awned, awns 0.5-18 mm long, sometimes subterminal. > 8
8 Disarticulation below the glumes. > 9
9 Spikelets borne on stipes; disarticulation at the base of the stipes; lemmas 0.5-2 mm long; glumes usually awned, sometimes unawned Polypogon
9 Spikelets borne on pedicels; disarticulation immediately below the glumes; lemmas 1.5-7.5 mm long; glumes usually unawned. > 10
10 Paleas absent or greatly reduced; lemma awns attached at midlength or below; glume bases often fused; rachillas not prolonged beyond the floret base Alopecurus
10 Paleas from 3/4 to nearly as long as the lemmas; lemma awns subterminal; glume bases not fused; rachillas usually prolonged beyond the base of the distal floret as a minute stub or slender bristle Cinna
8 Disarticulation above the glumes. > 9
11 Rachillas not prolonged beyond the base of the distal floret; paleas absent, minute, or subequal to the lemmas; lemmas 0.5-4 mm long. > 12
12 Lemmas usually glabrous, sometimes pubescent, unawned or awned, if awned, the awns usually shorter than 4.5 mm, sometimes to 10 mm long, basal, dorsal, subterminal, or terminal; veins usually not excurrent, if excurrent, not forming awnlike teeth; panicles often open, sometimes contracted and cylindrical Agrostis
12 Lemmas pilose and dorsally awned, awns 4.5-6 mm long; lateral lemma veins excurrent, forming 4 teeth, teeth sometimes awnlike; panicles dense Bromidium
11 Rachillas prolonged beyond the base of the distal floret; paleas at least 1/2 as long as the lemmas; lemmas 1-8 mm long. > 12
13 Plants annual; calluses glabrous or sparsely hairy; lemma apices entire; marginal veins not excurrent; awns subterminal Apera
13 Plants perennial; calluses usually abundantly, sometimes sparsely hairy, hairs 0.2-6.5 mm long; lemma apices denticulate or the marginal veins excurrent; awn attachment from nearly basal to subterminal. > 14
14 Lemma surfaces mostly glabrous; lemma apices denticulate; marginal lemma veins not excurrent Calamagrostis
14 Lemma surfaces hairy; lemma apices erose or toothed; marginal lemma veins excurrent Lachnagrostis
6 Lemmas unawned or, if awned, awns shorter than 2 mm. > 7
15 Disarticulation below the glumes. > 16
16 Glumes attached to stipes, disarticulation at the base of the stipes; glumes usually awned, awns flexuous Polypogon
16 Glumes attached to pedicels, disarticulation immediately beneath the glumes; glumes unawned or with stiff awns. > 17
17 Lemma awns subterminal; glume bases not fused; paleas from 3/4 to nearly as long as the lemmas; rachillas prolonged beyond the base of the distal floret for 0.1-1.3 mm Cinna
17 Lemma awns attached at midlength or below; glume bases often fused; paleas absent or greatly reduced; rachillas not prolonged beyond the base of the distal floret Alopecurus
15 Disarticulation above the glumes. > 16
18 Glumes 8-15 mm long; plants strongly rhizomatous Ammophila
18 Glumes 1-10 mm long; plants rhizomatous or not. > 19
19 Spikelets dorsally compressed; lemmas dark, coriaceous, lustrous, and glabrous Milium
19 Spikelets laterally compressed, sometimes weakly so; lemmas not simultaneously dark, coriaceous, lustrous, and glabrous. > 20
20 Lower glumes exceeded by the florets, upper glumes exceeded by to exceeding the florets; sheaths usually closed for up to 1/5 their length Arctagrostis
20 Both glumes subequal to or exceeding the florets; sheaths open to the base. > 21
21 Paleas absent or minute to subequal to the lemmas, not veined; rachillas not prolonged beyond the base of the distal florets; lemmas often unawned, sometimes awned, awn attachment basal to terminal Agrostis
21 Paleas more than 1/2 as long as the lemmas, 2-veined; rachillas prolonged beyond the base of the floret by at least 0.1 mm; lemmas often awned, awn attachment usually on the proximal 1/2 of the lemmas. > 22
22 Calluses hairy, hairs 0.5-4.5 mm long; lemmas usually awned, awns usually attached to the proximal 1/2, if the attachment higher, the callus hairs longer than 2 mm and/or the awns geniculate Calamagrostis
22 Calluses glabrous or with hairs to about 1 mm long; lemmas unawned or terminally awned, awns to 1(2.2) mm long. > 23
23 Glumes 4-9 mm long; sheaths closed for 1/2 - 2/3 their length; plants of arctic and subarctic regions Dupontia
23 Glumes 1.6-4.3 mm long; sheaths open; plants of western North America, from Alaska to California Podagrostis

POEAE SUBKEY II

1 One or both glumes exceeding the adjacent lemmas, sometimes exceeding the distal floret. > 2
2 All lemmas within a spikelet unawned or with awns shorter than 2 mm. > 3
3 Spikelets usually with 2 florets, lemmas of the lower florets unawned, lemmas of the upper florets awned, the awns strongly curved or hooked Holcus
3 Spikelets with 2-22 florets, all lemmas unawned or if awned, the awns straight. > 4
4 Leaf sheaths closed for at least 1/2 their length; caryopses falling free of the lemma and palea; plants of arctic or subarctic regions. > 5
5 Lemma apices obtuse; paleas subequal to the lemmas Arctophila
5 Lemma apices acute to acuminate; paleas shorter than the lemmas Dupontia
4 Leaf sheaths open for most of their length; caryopses usually falling with the lemma and palea attached; plants of temperate, arctic, or subarctic regions. > 5
6 Glumes 15-50 mm long; plants annual Avena
6 Glumes 0.4-9 mm long; plants annual or perennial. > 7
7 Lemmas inflated, about as wide as long, with broadly rounded backs; calluses glabrous; spikelets pendulous Briza
7 Lemmas not inflated, longer than wide, keeled to rounded over the midvein; calluses usually with hairs, sometimes glabrous; spikelets not pendulous. > 8
8 Plants annual; spikelets with 2 florets; lemmas evenly hairy, 3-veined Dissanthelium
8 Plants usually perennial, sometimes annual; spikelets with 2-10 florets; lemmas usually glabrous or with unevenly distributed hairs, never both annual and with evenly distributed hairs, 3-9-veined. > 9
9 Rachilla internodes hairy, hairs at least 1 mm long. > 10
10 Lemma apices truncate, erose to 2-4-toothed Deschampsia
10 Lemmas apices acute, bifid Trisetum
9 Rachilla internodes glabrous or with hairs shorter than 1 mm on the distal portion. > 10
11 Plants strongly rhizomatous; glumes 5-9 mm long Scolochloa
11 Plants not or weakly rhizomatous; glumes 0.4-9 mm long. > 12
12 Panicle branches densely pubescent, hairs 0.1-0.2 mm long; lemma apices entire, sometimes mucronate; lemma veins converging distally Koeleria
12 Panicles branches glabrous, sometimes scabrous; lemma apices entire or serrate to erose, not mucronate; lemma veins more or less parallel distally Puccinellia
2 One or all lemmas within a spikelet awned, the awns at least 2 mm long. > 3
13 Lemmas 14-40 mm long; glumes 7-11-veined Avena
13 Lemmas 1.3-16 mm long; glumes 1-9-veined. > 14
14 Lemmas 7-16 mm long. > 15
15 Adaxial surfaces of the leaves ribbed; rachillas pilose on all sides; ligules truncate to rounded, 0.5-1.5 mm long Helictotrichon
15 Adaxial surfaces of the leaves unribbed; rachillas glabrous on the side adjacent to the paleas, hairy elsewhere; ligules acute to truncate, 0.5-7 mm long Avenula
14 Lemmas 1.3-7 mm long. > 15
16 Lemmas 1-veined, awned, awns articulated near the middle, the proximal segment yellow-brown to dark brown, the distal segment pale green to whitish, the junction marked by a ring of minute, conical protuberances Corynephorus
16 Lemmas 3-7-veined, at least some lemmas awned, awns not articulated. > 17
17 Disarticulation below the glumes. > 18
18 Spikelets usually with 2 florets, the lower florets bisexual with unawned lemmas, the upper florets staminate or sterile with awned lemmas Holcus
18 Spikelets with 2-5 florets, all florets bisexual or sometimes the distal florets sterile; all lemmas awned Trisetum
17 Disarticulation above the glumes. > 18
19 Lowest lemma within a spikelet unawned or with a straight awn up to 4 mm long, the distal lemmas within a spikelet always awned, awns 10-16 mm long, geniculate Ventenata
19 All lemmas within a spikelet similarly awned or the awns of the lower lemmas longer than those of the upper lemmas, or the upper lemmas with awns shorter than 10 mm. > 20
20 Callus hairs about 1/2 as long as the lemmas; rachillas not prolonged or prolonged about 0.5 mm or less beyond the base of the distal floret; plants loosely cespitose Vahlodea
20 Calluses usually glabrous or the hairs much shorter than 1/2 the length of the lemmas, if about 1/2 as long, the rachillas prolonged more than 0.5 mm beyond the base of the distal floret and the plants usually densely cespitose. > 21
21 Plants annual; culms 1-60 cm tall; rachillas not prolonged beyond the base of the distal florets Aira
21 Plants perennial or annual; culms 5-150 cm tall; rachillas prolonged beyond the base of the distal florets, the prolongations hairy. > 22
22 Rachilla internodes glabrous or with hairs shorter than 1 mm on the distal portion; panicle branches densely pubescent, not scabrous Koeleria
22 Rachilla internodes hairy, hairs at least 1 mm long; panicles branches usually glabrous, sometimes scabrous. > 23
23 Lemma apices truncate, erose or 2-4-toothed Deschampsia
23 Lemmas apices acute, bifid Trisetum
1 Both glumes shorter than or subequal to the adjacent lemmas. > 2
24 Upper lemma(s) in a spikelet with hooked or geniculate awns, awns 2-16 mm long; lowest lemmas unawned or terminally awned, awns straight, to 4 mm long. > 25
25 Spikelets 9-15 mm long, with 2-20 florets; awns of the distal florets 10-16 mm long Ventenata
25 Spikelets 3-7 mm long, with 2 florets; awns of the distal floret 2-5 mm long Holcus
24 Lemmas all similarly awned or unawned. > 25
26 Lower lemmas with awns longer than 2 mm. > 27
27 Calluses hairy; rachillas prolonged beyond the base of the distal florets. > 28
28 Glumes shorter than the adjacent lemmas; ligules 4.5-20 mm long Amphibromus
28 Glumes subequal to the adjacent lemmas; ligules 0.5-6 mm long Trisetum
27 Calluses glabrous or sparsely hairy; rachillas sometimes prolonged beyond the base of the distal florets. > 28
29 Panicles dense, spikelike; plants annual Rostraria
29 Panicles not both dense and spikelike; plants perennial or annual. > 30
30 Anthers 1; plants annual Vulpia
30 Anthers 3; plants perennial. > 31
31 Leaves without auricles; blades flat, conduplicate, involute, or convolute Festuca
31 Lower leaves with auricles; blades flat Schedonorus
26 Lower lemmas unawned, mucronate, or with awns up to 2 mm long. > 27
32 Lemmas inflated, about as wide as long; spikelets pendulous Briza
32 Lemmas not inflated, longer than wide; spikelets appressed to divergent, not pendulous. > 33
33 Lemmas apices rounded, truncate, obtuse, or emarginate. > 34
34 Lemmas conspicuously 3-veined; lower glumes 0-3-veined. > 35
35 Lower glumes without veins; lemmas not keeled over the lateral veins Catabrosa
35 Lower glumes 1-3-veined; lemmas keeled over each vein Cutandia
34 Lemmas (3)5-9-veined, the veins often inconspicuous; lower glumes 1-5-veined. > 35
36 Inflorescences usually exceeded by the leaves; lemmas indurate at maturity; pedicels 0.5-0.8 mm thick; culms usually prostrate to procumbent, sometimes ascending; upper glumes 2.6-6.2 mm long Sclerochloa
36 Inflorescences exceeding the leaves at maturity; lemmas usually membranous at maturity, sometimes coriaceous; pedicels less than 0.5 mm thick; culms usually erect; upper glumes 0.7-4.5(9) mm long. > 37
37 Lower glumes about as long as the upper glumes but no more than 1/2 as wide; disarticulation below the glumes Sphenopholis
37 Lower glumes shorter than the upper glumes or subequal and more than 1/2 as wide; disarticulation above the glumes. > 38
38 Sheaths closed for more than 1/2 their length Arctophila
38 Sheaths open their entire length. > 39
39 Panicle branches stiff; lemmas coriaceous; plants annual; culms to 60 cm tall Desmazeria
39 Panicle branches flexible; lemmas usually membranous, sometimes coriaceous; plants usually perennial, sometimes annual or biennial; culms 2-145 cm tall. > 40
40 Lemma veins excurrent, lemma apices indistinctly 3-lobed or toothed; plants strongly rhizomatous, rhizomes succulent Scolochloa
40 Lemma veins not excurrent, lemma apices entire, serrate, or erose; plants sometimes rhizomatous, rhizomes not succulent. > 41
41 Lemma veins (5)7-9, prominent; plants of non-saline and non-alkaline habitats Torreyochloa
41 Lemma veins (3)5(7), inconspicuous or prominent; plants of saline and alkaline habitats Puccinellia
33 Lemma apices acute to acuminate, sometimes mucronate or shortly awn-tipped. > 34
42 Lemmas (3)5-9-veined, veins more or less parallel distally, conspicuous. > 43
43 Lemma veins (5)7-9; plants rhizomatous, growing in non-saline and non-alkaline habitats Torreyochloa
43 Lemma veins (3)5(7); plants not truly rhizomatous, sometimes the culms rooting at buried lower nodes, growing in saline and alkaline habitats Puccinellia
42 Lemmas 3-9-veined, veins converging distally, usually inconspicuous, sometimes conspicuous. > 43
44 Lemmas conspicuously 3-veined, keeled over each vein; panicle branches divaricate; plants annual Cutandia
44 Lemmas inconspicuously (3)5-9-veined, sometimes keeled over the midvein, not over the other veins; panicle branches divaricate or not; plants annual or perennial. > 45
45 Disarticulation below the glumes; lower glumes subequal to the upper glumes but no more than 1/2 as wide Sphenopholis
45 Disarticulation above the glumes, sometimes above the basal floret; lower glumes shorter than the upper glumes or, if subequal, more than 1/2 as wide. > 46
46 Panicle branches smooth, hairy, hairs soft Koeleria
46 Panicle branches smooth or scabrous, glabrous or strigose, never covered with soft hairs. > 47
47 Rachillas pilose, hairs at least 2 mm long (see Stipeae, p. 110) Ampelodesmos
47 Rachillas glabrous or with hairs shorter than 1 mm. > 48
48 Basal leaves with auricles Schedonorus
48 No leaves with auricles. > 49
49 Lemma veins parallel distally; plants of saline and alkaline habitats Puccinellia
49 Lemma veins converging distally; plants of many habitats, including saline habitats. > 50
50 Leaf blades with translucent lines on either side of the midvein, apices often prow-tipped; lemmas often with a tuft of hair at the base of the midvein; hila round to oval Poa
50 Leaf blades without translucent lines on either side of the midvein, apices not prow-tipped, often flat; lemmas without a tuft of hair below the midvein hila usually linear, always linear in perennial species. > 51
51 Plants perennial. > 52
52 Plants and florets bisexual; glumes not translucent; caryopses obovoid-oblong Festuca
52 Plants unisexual; glumes translucent; caryopses fusiform Leucopoa
51 Plants annual. > 52
53 Ligules up to 1 mm long; lemma apices mucronate or awned Vulpia
53 Ligules 1-4 mm long; lemma apices never awned, sometimes mucronate. > 54
54 Panicle branches up to 2 cm long, stiff, spikelet-bearing to the base; culms procumbent to erect Desmazeria
54 Panicles branches 2-10 cm long, flexible, spikelets confined to the distal portion; culms erect Eremopoa