Poaceae
Poaceae tribe Cynodonteae
grass family
annual or perennial, herbaceous or woody, usually erect or ascending, sometimes prostrate or decumbent for much of their length, occasionally climbing, rarely floating;
nodes prominent, sometimes concealed by the leaf sheaths;
internodes hollow or solid, bases meristematic; branching from the basal nodes only or from the basal, middle, and upper nodes;
basal branching extravaginal or intravaginal; branching from the upper nodes intravaginal, extravaginal, or infravaginal.
1-500 cm, not woody, usually not branched above the base.
usually open, often with coarse hairs at the top;
auricles rarely present;
ligules of hairs or membranous, if membranous, often ciliate, cilia sometimes longer than the membranous base;
blades often with stiff, coarse marginal hairs adjacent to the ligules, glabrous or variously pubescent elsewhere.
alternate, 2-ranked, each composed of a sheath and blade encircling the culm or branch;
sheaths usually open, sometimes closed, the margins fused for all or part of their length;
auricles (lobes of tissue extending beyond the margins of the sheaths on either side) sometimes present;
ligules usually present at the sheath-blade junction, particularly on the adaxial surface, abaxial ligules common in the Bambusoideae, membranous, sometimes ciliate, adaxial ligules usually present, of membranous to hyaline tissue, a line of hairs, or a ciliate membrane;
blades usually linear to lanceolate, occasionally ovate to triangular, bases sometimes pseudopetiolate (having a petiole-like constriction), venation usually parallel, sometimes with evident cross veins, occasionally divergent.
(synflorescences) usually compound, composed of simple or complex aggregations of primary inflorescences, aggregations paniculate, spicate, or racemose or of spikelike branches, often with an evident rachis (central axis), primary inflorescences spikelets, pseudospikelets, or spikelet equivalents;
inflorescence branches usually without obvious bracts.
terminal, sometimes also axillary, simple panicles, panicles of 1-many spikelike branches, spikelike racemes, spikes, or, in 1 genus, a solitary spikelet, in dioecious taxa the staminate and pistillate inflorescences sometimes morphologically distinct;
disarticulation usually beneath the fertile florets or the glumes but, particularly if the panicle branches are short, sometimes at the base of the branches.
with (0-1)2(3-6) glumes (empty bracts) subtending 1-60 florets, glumes and florets distichously attached to a rachilla (central axis);
pseudospikelets with bud-subtending bracts below the glumes.
usually laterally compressed, with 1-60 florets, sterile or reduced florets, if present, usually distal to the bisexual florets.
usually with an odd number of veins, sometimes awned.
from shorter than the adjacent florets to exceeding the distal florets;
lemmas 1-3-veined or 7-13-veined, rarely 5-veined, if with 7-13 veins, the veins often in 3 groups;
lodicules 2, or absent, x = 7, 8, 9, 10, 12.
bisexual, staminate, or pistillate, usually composed of a lemma (lower bract) and palea (upper bract), lodicules, and reproductive organs, often laterally or dorsally compressed, sometimes round in cross section;
lemmas usually with an odd number of veins, often awned, bases frequently thick and hard, forming a callus, backs rounded or keeled over the midvein, awns usually 1(-3), arising basally to terminally;
paleas usually with 2 major veins, with 0 to many additional veins between the major veins, sometimes also in the margins, often keeled over the major veins;
lodicules (0)2-3, inconspicuous, usually without veins, bases swelling at anthesis;
stamens usually 3, sometimes 1(2) or 6+, filaments capillary, anthers versatile, usually all alike within a floret, sometimes 1 or 2 evidently longer than the others;
ovaries 1-loculed, with (1)2-3(4) styles or style branches, stigmatic region usually plumose.
caryopses, pericarp usually dry and adhering to the seed, sometimes fleshy or dry and separating from the seed at maturity or when moistened;
embryos ⅕ as long as to almost equaling the caryopses, highly differentiated with a scutellum (absorptive organ), a shoot with leaf primordium covered by the coleoptile (shoot sheath), and a root covered by the coleorhiza (root sheath);
hila punctate to linear.
= 5,6, 7, 9, 10, 11, 12.
Poaceae
Poaceae tribe Cynodonteae
The Poaceae or grass family includes approximately 700 genera and 11,000 species (Chen et al. 2006). The two grass volumes in this series treat 10 subfamilies, 25 tribes, 236 genera, and 1373 species. Of these, all the subfamilies, 22 tribes, 136 genera, and 892 species are native to the Flora region; 2 tribes, 78 genera, and 290 species have become established in the region. The remaining taxa include ornamental species; species grown for research purposes; species that, if introduced to the region, would pose a threat to important agricultural species; and a few waifs, i.e., species that have been found in the region but have not become established. Most of the waifs are species that were found on ballast dumps near ports around the turn of the last century.
Grasses constitute the fourth largest plant family in terms of number of species. Nevertheless, the family is clearly more significant than any other plant family in terms of geographic, ecological, and economic importance. Grasses grow in almost all terrestrial environments, including dense forests, open deserts, and freshwater streams and lakes. There are no truly marine grasses, but some species grow within reach of the highest tides.
In addition to being widely distributed, grasses are often dominant or co-dominant over large areas. The importance of such areas to humans is reflected in the many words that exist for grasslands, words such as meadow, palouse, pampas, prairie, savanna(h), steppe, and veldt. Not surprisingly, given their abundance and prevalence, grasses are of great ecological importance as soil stabilizers and as providers of shelter and food for many different animals.
The economic importance of grasses to humans is almost impossible to overestimate. The wealth of individuals and countries is dependent on the availability of such sources of grain as Triticum (wheat), Oryza (rice), Zea (corn or maize), Hordeum (barley), Avena (oats), Secale (rye), Eragrostis (tef), and Zizania (wild rice). Most countries invest heavily in research programs designed to develop better strains of these grasses and the many other grasses that are used for livestock, soil stabilization, and revegetation. Developing improved grasses for recreation areas, such as playing fields, golf courses, and parks, is also a major industry in many parts of the world; increasing recognition of the aesthetic value af grasses is reflected in their prominence in horticultural catalogs.
There are, of course, grasses that are considered undesirable, at least in some parts of the world, but even the most obnoxious grasses may be well-regarded over a portion of their range. For instance, Bromus tectorum (cheatgrass) is a noxious, fire-prone invader of western North American ecosystems; it is also welcomed as a source of early spring feed in some parts of the Flora region. Cynodon dactylon (bermudagrass) is listed as a noxious weed in some jurisdictions; in others it is valued as a lawn grass.
Although grasses are widespread and often dominant in open areas, all evidence points to an origin of the family in forests, most likely in the Southern Hemisphere, at least 55-70 mya (Grass Phylogeny Working Group 2001). Recent evidence from phytoliths (isolated silica bodies commonly produced inside the epidermal cells of grasses and some other plants) embedded in fossil coprolites strongly suggests that grasses evolved earlier in the Cretaceous than previously thought (Prasad et al. 2005). Living representatives of the three earliest lineages of the grass family, together comprising about 30 species, are perennial, broad-leaved plants of relatively small stature, native to tropical or subtropical forests in South America, Africa, southeast Asia, some Pacific Islands, and northern Australia. The major diversification of the family probably occurred in the mid-Cenozoic, and was associated with climatic changes that produced more open habitats. All major lineages of the grass family were present by the middle of the Miocene (Jacobs et al. 1999), and C4 photosynthesis in grasses had evolved by then, as well.
Molecular and morphological data unequivocally support a single origin for the Poaceae (Grass Phylogeny Working Group 2001). The caryopsis, a single-seeded, usually dry and indehiscent fruit with the pericarp usually strongly adherent to the seed, and the laterally positioned, highly differentiated embryo are unique to grasses. Beyond the three early-diverging lineages (Anomochlooideae Potztal, Pharoideae, and Puelioideae L.G. Clark et al.), the great diversity of grasses can be divided into two major lineages: the BEP clade (Bambusoideae, Ehrhartoideae, and Pooideae); and the PACMCAD clade (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae Pilger, Centothecoideae, Aristidoideae, and Danthonioideae, i.e., the PACCAD clade of volume 25 plus the Micrairoideae, support for recognition of which was obtained after publication of that volume). Relationships among the BEP grass lineages remain uncertain, and some evidence points to the Pooideae as being more closely related to the PACMCAD clade than to the Bambusoideae or Ehrhartoideae. The PACMCAD clade includes all known C4 or warm-season grasses.
The closest relatives of the Poaceae lie within a group of six families, all native primarily to the Southern Hemisphere: Joinvilleaceae Toml. & A.C. Sm., Ecdeiocoleaceae D.F. Cutler &c& Airy Shaw, Restionaceae R. Br., Centrolepidaceae Endl., Anarthriaceae D.E Cutler &c& Airy Shaw, and Flagellariaceae Dumort. (Poales Small, sensu stricto). Joinvilleaceae, Ecdeiocoleaceae, and Poaceae constitute a three family clade, with Ecdeiocoleaceae probably being closer than Joinvilleaceae to the Poaceae (Bremer 2000; Bremer 2002; Michelangeli et al. 2003). Rudall et al. (2005), based on a study of reproductive structures in the Ecdeiocoleaceae, suggest that the grass caryopsis may represent "one end of a transformation series embodied by the reduced gynoecial structure and indehiscent fruit of other Poales such as Flagellaria and Ecdeiocolea" (p. 1441).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Most members of the Cynodonteae in the Flora region can be recognized by their possession of two or more of the following characteristics: 1-3- or 7-13-veined lemmas, laterally compressed spikelets, spikelike inflorescence branches, and the presence of coarse hairs near the junction of the sheath and blade. All employ the NAD-ME or PCK C4 photosynthetic pathways, have Kranz blade anatomy, and tend to grow in hot, dry areas. Having said this, it must be acknowledged that each of these characteristics can be found in other tribes and, within the Cynodonteae, there are genera that lack one or more of them.
The tribe Cynodonteae, as interpreted here, includes genera that are normally placed in two tribes, the Cynodonteae sensu stricto, and the Eragrostideae Stapf (Clayton and Renvoize 1986; Peterson et al. 2001; Grass Phylogeny Working Group 2001, but see Campbell 1985). Genera 17.01 to 17.34 correspond to the Eragrostideae and genera 17.35 to 17.53 to their Cynodonteae. The two are treated as one here because recent morphological, anatomical, and molecular studies (Van den Borre 1994; Van den Borre and Watson 1997; Hilu and Alice 2001) indicate that the distinction between the two is artificial. There is, however, no agreement on an alternative treatment as is indicated by Peterson et al. (2001) who listed 23 of the 53 genera treated here as being of uncertain position within the subfamily Chloridoideae. Part of the problem is that several of the genera (e.g., Eragrostis, Chloris, Muhlenbergia, and Sporobolus) are polythetic (Van den Borre and Watson 1997; Hilu and Alice 2001).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key to Tribes
1. Leaf blades with divergent veins; spikelets unisexual and dimorphic, the pistillate lemmas with uncinate hairs (Pharoideae; FNA 24:11) | Phareae |
1. Leaf blades with parallel veins; spikelets bisexual, unisexual, or modified into plantlets, the pistillate lemmas never with uncinate hairs. | → 2 |
2. Culms perennial, woody or herbaceous, often developing complex branching systems from the upper nodes; leaves on the upper portion of the culms, or distal on the branches, usually pseudopetiolate (Bambusoideae). | → 3 |
3. Culms woody, to 30 m tall; leaves strongly dimorphic, those of the main culms (culm leaves) with expanded sheaths and often with reduced, non-photosynthetic blades, those of the branches (foliage leaves) with abaxial ligules; blades of the distal leaves not folding at night or under stress; florets bisexual; plants native or introduced, often cultivated (FNA 24:15) | Bambuseae |
3. Culms herbaceous, to 3.5 m tall or climbing; leaves not strongly dimorphic; blades of the distal leaves often folding at night or under stress; florets unisexual; plants known only in cultivation in the Flora region (FNA 24:29) | Olyreae |
2. Culms usually annual, sometimes facultatively perennial, rarely woody, sometimes branching from the upper nodes but the branching system not complex; leaves usually not pseudopetiolate. | → 4 |
4. Spikelets almost always with 2 florets, the lower florets in the spikelets always sterile or staminate, frequently reduced to lemmas, occasionally missing, the upper florets bisexual, staminate, or sterile, unawned or awned from the lemma apices or, if the lemmas bilobed, from the sinuses; glumes membranous and the upper lemma stiffer than the lower lemma, or both florets reduced and concealed by the stiff to coriaceous glumes; rachilla not prolonged beyond the second floret (Panicoideae, in part). | → 5 |
5. Glumes flexible, membranous, the lower glumes usually shorter than the upper glumes, sometimes missing, the upper glumes usually subequal to or exceeded by the upper floret; lower lemmas membranous; upper lemmas usually coriaceous to indurate, sometimes membranous; upper paleas similar in texture; spikelets usually single or in pairs, occasionally in triplets and all pedicellate, often shortly so) (FNA 25:353) | Paniceae |
5. Glumes stiff, coriaceous to indurate, often subequal, at least 1 and usually both exceeding the upper floret (excluding the awn); both lemmas hyaline; paleas hyaline or absent; most spikelets in pairs or triplets, at least 1 spikelet in each group usually sessile; pedicels shorter or only a little longer than the sessile spikelets (FNA 25:602) | Andropogoneae |
4. Spikelets either with other than 2 florets or, if with 2, the lower floret bisexual or the upper floret awned from the back or base of the lemma, or the spikelets bulbiferous; glumes usually membranous; lemmas scarious to indurate; rachilla sometimes prolonged beyond the distal floret. | → 6 |
6. Spikelets with 1 floret; lemmas terminating in a 3-branched awn (the lateral branches sometimes greatly reduced); callus well developed; ligules usually of hairs, sometimes ciliate membranes, the cilia longer than the membranous base (Aristidoideae; FNA 25:314) | Aristideae |
6. Spikelets with more than 1 floret or, if only 1, the lemma not terminating in a 3-branched awn; callus development various; ligules various. | → 7 |
7. Spikelets with 1 sexual floret or the spikelets bulbiferous; glumes absent or less than ¼ as long as the adjacent floret; lower glumes, if present, without veins, upper glumes, if present, veinless or 1-veined. | → 8 |
8. Upper glumes present, 1-veined; lower glumes absent or much shorter than the upper glumes and lacking veins (Pooideae, in part; FNA 24:57) | Brachyelytreae |
8. Both glumes absent or lacking veins. | → 9 |
9. Inflorescences 1-sided spikes; triangular in cross section, [Pooideae, in part; FNA 24:62) | Nardeae |
9. Inflorescences panicles; spikelets laterally compressed or terete. | → 10 |
10. Culms aerenchymatous, 20-500 cm long; plants of wet places, often emergent, sometimes floating; lemmas of the bisexual or pistillate florets 3-14-veined; paleas 3-10-veined (Ehrhartoideae, in part; FNA 24:36) | Oryzeae |
10. Culms not aerenchymatous, 2-300 cm tall; plants of wet or dry habitats but not emergent or floating; lemmas of the bisexual or pistillate florets 1-3-veined; paleas 2-veined. | → 11 |
11. Culms 2-19 cm tall; plants of cold or damp habitats, not rhizomatous; sheaths of the flag leaves closed for at least 1/2 their length; caryopses exposed at maturity (Pooideae, in part; FNA 24:378) | Poeae |
11. Culms 5-300 cm tall; plants usually of warm or dry habitats, often rhizomatous; sheaths of the flag leaves open to the base; caryopses not exposed at maturity (Chloridoideae, in part; FNA 25:14) | Cynodonteae |
7. Spikelets usually with more than 1 sexual floret; usually with 2 glumes, 1 or both glumes often longer than ¼ the length of the adjacent floret and/or with more than 1 vein, always longer in taxa with 1 sexual floret. | → 12 |
12. Lemmas unawned, flabellate or with (5)7-15 awnlike teeth (Chloridoideae, in part). | → 13 |
13. Plants not viscid, usually perennial; ligules present, composed of hairs (FNA 25:285) | Pappophoreae |
13. Plants viscid annuals; ligules absent (FNA 25:290) | Orcuttieae |
12. Lemmas awned or unawned, lanceolate, rectangular, or ovate, apices entire, mucronate, bilobed, or bifid, occasionally 4-lobed or 4-5-toothed, sometimes erose. | → 14 |
14. Cauline leaf sheaths closed for 1/2 their length or more; glumes usually exceeded by the distal florets, sometimes greatly so (Pooideae, in part). | → 15 |
15. Spikelets 5-80 mm long, not bulbiferous; lemmas usually awned, often bilobed or bifid, veins convergent distally; ovary apices hairy (FNA 24:193) | Bromeae |
15. Spikelets 0.7-60 mm long, sometimes bulbiferous; lemmas often unawned, not both bilobed/bifid and with convergent veins; ovary apices usually glabrous. | → 16 |
16. Lemma veins (4)5-15, usually prominent, parallel distally; spikelets 2.5-60 mm long, not bulbiferous (FNA 24:67) | Meliceae |
16. Lemmas veins 1-9, often inconspicuous, usually convergent distally; spikelets 0.7-18(20) mm long, sometimes bulbiferous (FNA 24:378) | Poeae |
14. Cauline leaf sheaths open for at least 1/2 their length; glumes exceeding or exceeded by the distal florets. | → 17 |
17. Spikelets with 1 floret; lemmas terminally or subterminally awned, the junction of the awn and lemma conspicuous; rachillas not prolonged beyond the base of the floret (Pooideae, in part; FNA 24:109) | Stipeae |
17. Spikelets with 1-60 florets; lemmas unawned or awned, awns basal to terminal, if terminal or subterminal, the lemma-awn junction not conspicuous; rachillas often prolonged beyond the base of the distal floret. | → 18 |
18. Ligules, at least of the flag leaves, of hairs, a ciliate ridge or membrane bearing cilia longer than the basal ridge or membrane; leaves usually hairy on either side of the ligule; auricles absent. | → 19 |
19. Lemmas of the fertile florets with 3-11 inconspicuous veins, never glabrous, if with 3 veins, pilose throughout or with transverse rows of tufts of hair, if with 5-11 veins, the margins pilose proximally, the hairs not papillose-based; lemma apices usually bilobed or bifid and awned or mucronate from the sinus, if acute to acuminate, the lemmas pilose; awns twisted proximally (Danthonioideae; FNA 25:298) | Danthonieae |
19. Lemmas of the fertile florets usually with 1-3 conspicuous veins, sometimes with 3 inconspicuous veins or 5-11 veins, often glabrous, if with 3 veins, usually glabrous throughout or hairy over the veins, sometimes the margins with papillose-based hairs; lemma apices acute to obtuse, bilobed, or 4-lobed, often mucronate or awned from the sinuses; awns usually not twisted. | → 20 |
20. Lemmas 1-11-veined, veins glabrous or hairy, margins without papillose-based hairs; rachillas and calluses not pilose, sometimes strigose or strigulose; basal internodes of the culms not persistent, not swollen and clavate (Chloridoideae, in part; FNA 25:14) | Cynodonteae |
20. Lemmas 3(5)-veined, veins glabrous, margins sometimes with papillose-based hairs; rachillas or calluses pilose or the basal internodes of the culms persistent, often swollen and clavate (Arundinoideae, in part; FNA 25:7) | Arundineae |
18. Ligules membranous, if ciliate, the cilia shorter than the membranous base; leaves usually glabrous on either side of the ligule; auricles present or absent. | → 21 |
21. Inflorescences panicles or unilateral racemes, not spikelike, without spike-like branches; spikelets solitary, the lowest 0-4 florets in a spikelet sterile or staminate, the distal florets sexual. | → 22 |
22. Spikelets with (1)2-25 bisexual florets; all lemmas similar in size and shape; glumes and lemmas membranous (Centothecoideae). | → 23 |
23. Culms 35-150 cm tall; spikelets with (2)3-26 florets, including the lowest (0)1-4 sterile or staminate florets; lower glumes (1)2-9-veined (FNA 25:344) | Centotheceae |
23. Culms 150-400 cm tall; spikelets with 2-4 florets, including the lowest sterile floret; glumes 0-1-veined (FNA 25:349) | Thysanolaeneae |
22. Spikelets with 1 bisexual or unisexual floret; lemmas of the sterile florets usually differing in size and shape from those of the sexual floret; glumes membranous, lemmas of the sexual florets firmer. | → 24 |
24. Lemmas of the lower florets coriaceous, at least the upper exceeding the sexual floret (Ehrhartoideae, in part; FNA 24:33) | Ehrharteae |
24. Lemmas of the lower florets membranous, often both much shorter than the sexual floret, sometimes subequal to it, sometimes only 1 sterile floret present (Pooideae, in part; FNA 24:378) | Poeae |
21. Inflorescences panicles, racemes, or spikes; spikelets sometimes in pairs or triplets, sterile florets, if any, distal to the bisexual or pistillate florets. | → 25 |
25. Lemmas with 1-3 or 9-11 conspicuous veins; sheaths open; blade cross sections with Kranz leaf anatomy (Chloridoideae, in part; FNA 25:14) | Cynodonteae |
25. Lemmas with (1)3-15 often inconspicuous veins, if with 3 conspicuous veins, the sheaths closed; sheaths open or closed; blade cross sections without Kranz leaf anatomy. | → 26 |
26. Inflorescences spikes or spikelike; spikelets 1-5+ per node, at least 1 spikelet sessile or subsessile (Pooideae, in part). | → 27 |
27. Upper glumes 5-9-veined; spikelets subsessile and solitary at the nodes; auricles absent (FNA 24:187) | Brachypodieae |
27. Upper glumes 1-5-veined; spikelets 1-5+ per node, usually at least 1 sessile at each node, sometimes highly reduced branches present; auricles present or absent. | → 28 |
28. Inflorescences with 1-5 spikelets at a node, if 3, usually with 1 sessile and 2 pedicellate spikelets, if 1, the spikelet tangential to or embedded in the rachis, with 2 glumes, the glumes facing each other; ovaries with hairy apices; auricles often present (FNA 24:238) | Triticeae |
28. Inflorescences spikelike panicles with highly reduced branches, or spikes with spikelets radial to the rachises and all but the terminal spikelet with only 1 glume, or spikes with spikelets tangential to the rachises and having 2 glumes adjacent to each other; ovaries with glabrous apices; auricles usually absent (FNA 24:378) | Poeae |
26. Inflorescences panicles, with no sessile spikelets. | → 29 |
29. Caryopses with a thick pericarp forming a distinct apical knob or beak at maturity; lemmas 3(5)-veined (Pooideae, in part; FNA 24:64) | Diarrheneae |
29. Caryopses usually with a thin pericarp, never with a distinct apical beak or knob; lemmas 3-9-veined. | → 30 |
30. Glumes subulate, stiff; lemmas unawned or with awns to 4 mm long (Pooideae, in part; FNA 24:238) | Triticeae |
30. Glumes lanceolate, membranous; lemmas awned or unawned, awn length varied. | → 31 |
31. Rachillas hairy, hairs 2-3 mm long; lemmas coriaceous; plants established in California, sometimes cultivated as ornamentals (Pooideae, in part; FNA 24:109) | Stipeae |
31. Rachillas glabrous to hairy, hairs shorter than 2 mm; lemmas membranous to coriaceous; plants native, established, or cultivated. | → 32 |
32. Leaves to 2 cm wide, usually not conspicuously distichous; culms 0.01-2.75 m tall, usually less than 1 cm thick (Pooideae, in part; FNA 24:378) | Poeae |
32. Leaves 2-10 cm wide, often conspicuously distichous; culms 2-10(15) m tall, often more than 1 cm thick. | → 33 |
33. Lower cauline blades disarticulating, upper cauline blades forming a flat, fan-shaped arrangement (Panicoideae, in part; FNA 25:352) | Gynerieae |
33. Lower cauline blades persistent, upper cauline blades not forming a flat, fan-shaped arrangement (Arundinoideae, in part; FNA 25:7) | Arundineae |
1. Inflorescences clearly exceeded by the upper leaves, often completely or almost completely enclosed in the upper leaf sheaths; culms 1-30(75) cm tall. | → 2 |
2. Lemmas 3-lobed, the lobes ciliate; spikelets with 4 florets | Blepharidachne |
2. Lemmas not 3-lobed or the lobes not ciliate; spikelets with 1-60 florets. | → 3 |
3. Spikelets (and often the plants) unisexual. | → 4 |
4. Leaves strongly distichous; lemmas 9-11-veined; plants unisexual, growing in saline and alkaline soils. | → 5 |
5. Pistillate and staminate inflorescences consisting of a single spikelet | Monanthochloë |
5. Pistillate and staminate inflorescences consisting of more than 1 spikelet | Distichlis |
4. Leaves not strongly distichous; lemmas 1-5-veined; plants unisexual or, if bisexual, with separate pistillate and staminate inflorescences, growing in a variety of soils. | → 6 |
6. Spikelets 5-26 mm long; pistillate and staminate inflorescences similar, simple panicles; glumes and lemmas unawned, mucronate, or 1-awned | Eragrostis |
6. Spikelets 2.5-7 mm long; pistillate and staminate inflorescences strongly dimorphic; staminate inflorescences with pectinate, spikelike branches; pistillate spikelets with conspicuously 3-awned glumes or distal florets. | → 7 |
7. Upper glumes of the pistillate spikelets white, rigid, globose structures termin¬ating in 3 awnlike teeth; pistillate spikelets with 1 floret, without rudimentary florets, the floret unawned or shortly 3-awned; staminate spikelets 4-6 mm long; anthers 2.5-3 mm long, brownish, red, or orange; widespread species of the central plains | Buchloë |
7. Upper glumes of the pistillate spikelets membranous, unawned; pistillate spikelets with one 3-awned floret and a distal 3-awned rudiment; staminate spikelets 3-4 mm long; anthers 2-2.5 mm long, pale; known, within the Flora region, only from Florida | Opizia |
3. Spikelets bisexual, usually at least the lowest floret in each spikelet bisexual, in Dasyochloa the third floret in each spikelet bisexual or pistillate, if pistillate, the lowest 2 florets staminate. | → 8 |
8. Lemma margins with a tuft of hairs at midlength, glabrous elsewhere; blades with white, thickened margins and sharply pointed | Munroa |
8. Lemma margins glabrous, or with hairs but the hairs not forming a tuft at midlength; blades without white cartilaginous margins, not sharply pointed. | → 9 |
9. Lemmas awned, the awns 1-11 mm long. | → 10 |
10. Plants stoloniferous; inflorescences 1-2.5 cm long, dense panicles; lemmas bilobed, the lobes about 1/2 as long as the lemmas; ligules of hairs | Dasyochloa |
10. Plants not stoloniferous; inflorescences 1.5-76 cm long, not dense; lemmas entire or minutely bilobed; ligules membranous, sometimes ciliate | Leptochloa |
9. Lemmas unawned, sometimes mucronate, with mucros less than 1 mm long. | → 11 |
11. Spikelets with 2-20 florets; inflorescences panicles of 2-120 spikelike branches | Leptochloa |
11. Spikelets with 1(3) florets; inflorescences simple panicles, often highly contracted, without spikelike branches. | → 12 |
12. Inflorescences 0.3-7.5 cm long, dense, spikelike or capitate panicles 1-8 times longer than wide; glumes strongly keeled; plants annual | Crypsis |
12. Inflorescences 1-60 cm long, sometimes dense and spikelike but, if less than 8 cm long, more than 8 times longer than wide; glumes rounded or weakly keeled; plants annual or perennial | Sporobolus |
1. Inflorescences usually equaling or exceeding the upper leaves; culms 1-500 cm tall. | → 13 |
13. Inflorescences with disarticulating branches, disarticulation at the base of the branches or (in Lycurus) the fused pedicels; branches 0.04-7 cm long, often globose or spikelike (fused to the rachis and not evident in Lycurus), usually with fewer than 15 spikelets per branch. | → 14 |
14. Upper glumes with straight or uncinate spinelike projections; spikelets crowded, the branches condensed into burs | Tragus |
14. Upper glumes without spinelike projections; spikelets sometimes crowded, but not forming bur like clusters. | → 15 |
15. Branches not fused to the rachises; spikelets more than 3 per branch, usually all alike, sometimes the proximal spikelet sterile or replaced with short secondary branches. | → 16 |
16. Both glumes much longer than the florets, usually exceeding the distal florets; plants annual | Dinebra |
16. Lower glumes shorter than or subequal to the lower florets, 1 or both glumes usually exceeded by the distal florets; plants usually perennial. | → 17 |
17. Spikelets with 1-2(3) florets; branches disarticulating promptly, before the spikelets disarticulate | Bouteloua |
17. Spikelets with 2-8 florets; branches disarticulating tardily, initially the spikelets disarticulating above the glumes | Pogonarthria |
15. Branches sometimes fused to the rachises; spikelets 1-3 per branch, usually some spikelets on each branch sterile or staminate and 1 pistillate or bisexual. | → 18 |
18. Axes of the branches extending beyond the base of the distal florets | Bouteloua |
18. Axes of the branches terminating at the base of the distal spikelet. | → 19 |
19. Spikelets in pairs; glumes awned, the lower glumes (1)2(3)-awned, the upper glumes 1-awned; panicle branches often fused to the rachises | Lycurus |
19. Spikelets in triplets; glumes unawned, 1-awned, or 3-awned; panicle branches sometimes appressed, but not fused, to the rachises. | → 20 |
20. Branches straight at the base; central spikelets sessile | Hilaria |
20. Branches sharply curved at the base; central spikelets sessile or pedicellate. | → 21 |
21. Central spikelets with 1 bisexual floret; lateral spikelets with 1 floret, varying to rudimentary | Aegopogon |
21. Central spikelets with 3-4 florets, the lowest floret pistillate, bisexual, or staminate, the distal florets staminate or sterile; lateral spikelets usually with 2 florets | Cathestecum |
13. Inflorescences without disarticulating branches; branches, if present, often more than 4.5 cm long, variously shaped, including spikelike but not globose, often with more than 16 spikelets per branch. | → 22 |
22. Inflorescences spikes or racemes. | → 23 |
23. Spikelets with 1 bisexual or staminate floret and no additional florets. | → 24 |
24. Rachises falcate or curved; both glumes exceeding the florets | Microchloa |
24. Rachises straight; lower glumes exceeded by the florets, sometimes absent. | → 25 |
25. Spikelets solitary at each node; disarticulation below the glumes or the spikelets not disarticulating | Zoysia |
25. Spikelets paired, terminal on branches that are fused to the rachises; disarticulation at the base of the fused pedicel pairs | Lycurus |
23. Spikelets with more than 1 floret but sometimes only 1 floret bisexual, the additional florets sterile or staminate. | → 26 |
26. All spikelets unisexual, the functional florets either staminate or pistillate; plants either unisexual or with both pistillate and staminate spikelets. | → 27 |
27. Lemmas 9-11-veined; plants of saline habitats | Distichlis |
27. Lemmas 3-veined; plants of various habitats. | → 28 |
28. Lemmas of the pistillate florets with awns 3.4-6.8 mm long; branches of staminate inflorescences pectinate; staminate spikelets with 1 floret | Opizia |
28. Lemmas of the pistillate florets with awns 30-150 mm long; branches of staminate inflorescences not pectinate; staminate spikelets with 5-20 florets | Scleropogon |
26. Some or all spikelets bisexual, the florets bisexual or unisexual, but both staminate and pistillate florets present within an individual spikelet. | → 29 |
29. Lemmas of the pistillate or bisexual florets with awns 30-150 mm long; bisexual florets rarely found | Scleropogon |
29. Lemmas of the bisexual florets unawned or with awns less than 10 mm long; pistillate florets not present. | → 30 |
30. Inflorescences 5-15 cm long, apparently a pectinate spike, actually a solitary, pectinate, spikelike branch | Ctenium |
30. Inflorescences 1.5-10 cm long, spikes, spikelike racemes, or panicles, linear or densely cylindrical to ovoid. | → 31 |
31. Inflorescences linear, (1.5)4-10 cm long; rachises not concealed by the spikelets | Tripogon |
31. Inflorescences cylindrical to ovoid, 1.5-5 cm long; rachises concealed by the spikelets | Fingerhuthia |
22. Inflorescences simple panicles (sometimes highly condensed) or panicles of 1-120 spikelike branches. | → 32 |
32. Inflorescences simple panicles, sometimes highly contracted, even spikelike in appearance; spikelike branches not evident [for opposite lead, see p. 19]. | → 33 |
33. Spikelets usually with only 1 floret, occasionally with 2-3 florets. | → 34 |
34. Ligules membranous, hyaline, or coriaceous, sometimes ciliate; lemmas 3-veined (occasionally appearing 5-veined), usually awned, sometimes unawned or mucronate. | → 35 |
35. Lemmas and paleas densely sericeous over the veins and margins, glabrous between the veins | Blepharoneuron |
35. Lemmas and paleas glabrous to variously hairy but not densely sericeous over the veins and margins. | → 36 |
36. Lemmas usually awned or mucronate; spikelets usually with 1 floret | Muhlenbergia |
36. Lemmas unawned or mucronate; spikelets frequently with 2-3 florets | Eragrostis |
34. Ligules of hairs; lemmas 1(3)-veined, unawned, sometimes mucronate. | → 37 |
37. Panicles 0.3-4(7.5) cm long, 3-15 mm wide, spikelike or capitate, 1-8 times longer than wide; plants annual | Crypsis |
37. Panicles 1-80 cm long, 2-600 mm wide, dense to open, if less than 8 cm long, often 10 or more times longer than wide; plants annual or perennial. | → 38 |
38. Calluses usually glabrous or almost so; paleas glabrous; fruits falling free of the lemma and palea | Sporobolus |
38. Calluses evidently hairy, the hairs 1/4 - 7/8 as long as the lemmas; paleas hairy; fruits falling with the lemma and palea | Calamovilfa |
33. Spikelets with more than 1 floret. | → 39 |
39. Lemmas with (5)9-11 veins (the lateral veins obscure in Allolepis). | → 40 |
40. Spikelets unisexual; plants almost always unisexual, occasionally bisexual. | → 41 |
41. Lemmas 9-11-veined; glumes 2-7 veined; plants rhizomatous and/or stoloniferous, found in saline or alkaline soils | Distichlis |
41. Lemmas 1-6-veined; lower glumes of the staminate spikelets 1-veined, those of the pistillate spikelets 1-5-veined; plants stoloniferous or rooting at the lower nodes, not rhizomatous, not found in saline or alkaline soils. | → 42 |
42. Plants perennial, stoloniferous; paleas of the pistillate florets completely surrounding the ovaries, the intercostal region coriaceous | Allolepis |
42. Plants annual, rooting at the lower nodes; paleas of the pistillate florets not completely surrounding the ovaries, the intercostal region membranous or hyaline | Eragrostis |
40. All spikelets with at least 1 bisexual floret. | → 43 |
43. Glumes longer than the adjacent lemmas. | → 44 |
44. Glumes exceeded by the distal florets; spikelets with 3-7 bisexual florets plus reduced distal florets; lemmas of the bisexual florets 5-7-veined throughout | Swallenia |
44. Glumes exceeding the distal florets; spikelets with 2-4 florets, only the lowest floret bisexual; lemmas of the bisexual florets 3-veined basally, 5-7-veined distally | Fingerhuthia |
43. Glumes shorter than the adjacent lemmas. | → 45 |
45. Spikelets ovate-elliptical to ovate-triangular, 15-50 mm long, 6-16 mm wide; lower florets sterile, without paleas | Uniola |
45. Spikelets usually elliptical to lanceolate, 1-26 mm long, 0.6-9 mm wide; lower florets in each spikelet bisexual, with paleas. | → 46 |
46. Calluses glabrous or sparsely pubescent; lemmas (1)3(5)-veined; spikelets 1-26 mm long, 0.6-9 mm wide | Eragrostis |
46. Calluses densely pubescent; lemmas 5-, 7-, or 9-veined; spikelets 10-16 mm long, 2.5-5 mm wide | Vaseyochloa |
39. Lemmas with 1-3 veins (occasionally with scabrous lines that may be mistaken for additional veins). | → 47 |
47. Florets unisexual. | → 48 |
48. Staminate and pistillate florets strongly dimorphic; plants unisexual or bisexual, bisexual plants with unisexual or bisexual spikelets; pistillate spikelets with 3-5 functional florets and lemma awns (30)50-150 mm long; staminate spikelets with 5-10(20) florets and unawned or shortly awned (to 3 mm) lemmas | Scleropogon |
48. Staminate and pistillate florets similar; plants unisexual; spikelets with 4-60 florets, all or almost all functional; lemmas 1.5-10.5 mm, unawned, sometimes mucronate. | → 49 |
49. Plants perennial, stoloniferous; paleas of the pistillate florets completely surrounding the ovaries, the intercostal region coriaceous | Allolepis |
49. Plants annual, rooting at the lower nodes; paleas of the pistillate florets not completely surrounding the ovaries, the intercostal region membranous or hyaline | Eragrostis |
47. At least 1 floret in each spikelet bisexual. | → 50 |
50. Lemmas, including the calluses, glabrous or inconspicuously hairy; lemma apices usually entire, sometimes minutely toothed. | → 51 |
51. Spikelets with (1)2-60 florets; lemmas unawned, sometimes mucronate; ligules usually membranous and ciliate or ciliolate, sometimes of hairs | Eragrostis |
51. Spikelets with 1(2-3) florets; lemmas often awned, sometimes unawned or mucronate; ligules membranous, sometimes ciliolate, not ciliate | Muhlenbergia |
50. Lemma bodies conspicuously hairy over the veins and/or calluses conspicuously hairy; lemma apices usually with emarginate, bilobed, or trilobed apices, sometimes entire. | → 52 |
52. Leaf margins evidently cartilaginous | Erioneuron |
52. Leaf margins not cartilaginous. | → 53 |
53. Palea keels long hairy distally, the distal hairs 0.5-2 mm long | Triplasis |
53. Palea keels glabrous or with hairs less than 0.5 mm long. | → 54 |
54. Lemmas unawned, the midveins sometimes excurrent up to 0.5 mm. | → 55 |
55. Lemmas rounded to truncate, emarginate to bilobed; all 3 lemma veins often pilose basally | Tridens |
55. Lemmas acute, entire or with 3 minute teeth, glabrous or shortly pubescent on the distal 2/3, the pubescence not confined to the veins | Redfieldia |
54. Lemmas awned, the awns 1-7 mm long. | → 56 |
56. Plants 80-500 cm tall; panicles 35-73 cm long, plumose; lemma margins pilose; lemma apices bifid, awned from between the teeth; awns about 3 mm long | Neyraudia |
56. Plants to 2-90 cm tall; panicles 6-30 cm long, not plumose; lemma margins sparsely pilose; lemma apices 3-4-lobed or -toothed and 3-awned; central awns 5-7 mm long, lateral awns 6-7 mm long | Triraphis |
32. Inflorescences panicles of spikelike branches, the branches digitately or racemosely arranged on the rachises [for opposite lead, see p. 18]. | → 57 |
57. Inflorescence branches 1 or more, if more than 1, arranged in terminal, digitate clusters, sometimes with additional branches or whorls below the terminal cluster. | → 58 |
58. Inflorescences with 1(2) falcate branches. | → 59 |
59. Spikelets with 2 well-developed sterile or staminate florets below the bisexual florets; additional sterile or staminate florets present distal to the bisexual floret | Ctenium |
59. Spikelets usually with 1, rarely 2, florets, the lowest or only floret bisexual | Microchloa |
58. Inflorescences with more than 1 branch or, if only 1, the branch not strongly falcate. | → 60 |
60. Plants unisexual. | → 61 |
61. Staminate spikelets 4-6 mm long, with 2 florets; upper glumes of the pistillate spikelets indurate, white | Buchloë |
61. Staminate spikelets 3-4 mm long, with 2 florets; upper glumes of the pistillate spikelets membranous | Opizia |
60. Plants bisexual, all spikelets with at least 1 bisexual floret. | → 62 |
62. Spikelets with more than 1 bisexual floret. | → 63 |
63. Panicle branches 0.4-7 cm long, terminating in a point | Dactyloctenium |
63. Panicle branches 1-22 cm long, terminating in a functional or rudimentary spikelet. | → 64 |
64. Disarticulation eventually below the glumes, initially below the lemmas and caryopses, the paleas persistent; panicle branches terminating in a rudimentary spikelet | Acrachne |
64. Disarticulation above the glumes, usually also below the florets; panicle branches terminating in a functional spikelet. | → 65 |
65. Lemmas 3-awned, the central awns 8-12 mm long | Trichloris |
65. Lemmas not 3-awned. | → 66 |
66. Lemmas usually with hairs over the veins, at least basally, the apices often toothed, sometimes mucronate or awned | Leptochloa |
66. Lemmas glabrous, the apices entire, neither mucronate nor awned | Eleusine |
62. Spikelets usually with only 1 bisexual floret (occasionally 2 in some genera), often with additional staminate, sterile, or modified florets. | → 67 |
67. Spikelets usually without sterile or modified florets; lemmas unawned | Cynodon |
67. Spikelets with 1 or more sterile florets distal to the bisexual floret; lemmas of the bisexual florets often awned. | → 68 |
68. Lowest lemmas in the spikelets 3-awned, the central awns 8-12 mm long, the lateral awns 0.5-12 mm long | Tricbloris |
68. Lowest lemmas in the spikelets usually unawned or with a single awn, if 3-awned, the lateral awns less than 0.5 mm long. | → 69 |
69. Spikelets dorsally compressed | Enteropogon |
69. Spikelets laterally compressed or terete. | → 70 |
70. Upper glumes truncate or bilobed; lowest lemmas unawned or with an awn to 1.2 mm long | Eustachys |
70. Upper glumes acute to acuminate; lowest lemmas usually awned, the awns to 37 mm long | Chloris |
57. Inflorescence branches more than 1, racemosely arranged on the rachises. | → 71 |
71. All spikelets unisexual. | → 72 |
72. Staminate spikelets 4-6 mm long, the anthers 2.5-3 mm long; pistillate spikelets with 1 unawned or shortly awned floret; wide spread species of the central plains | Buchloë |
72. Staminate spikelets 3-4 mm long, the anthers 2-2.5 mm long; pistillate lemmas with awns 3.4-6.8 mm long; in the Flora region, known only as an occasional escape from lawns and experimental plots in Florida | Opizia |
71. All spikelets with at least 1 bisexual floret. | → 73 |
73. Inflorescence branches woody, terminating in hard, sharp points | Cladoraphis |
73. Inflorescence branches not particularly stiff or rigid, terminating in spikelets or points. | → 74 |
74. Spikelets with more than 1 bisexual floret, sometimes also with reduced florets. | → 75 |
75. Lemmas 7-11-veined, mucronate, the mucros 0.1-0.3 mm long; not established in the Flora region | Aeluropus |
75. Lemmas 3-veined, unawned, mucronate, or awned, the awns often much more than 1 mm long; established in the Flora region. | → 76 |
76. Lower glumes exceeding the lowest lemmas, sometimes exceeding the distal lemmas | Trichoneura |
76. Lower glumes not or only slightly exceeding the lowest lemmas. | → 77 |
77. Inflorescences with 50 or more closely spaced, arcuate, tardily deciduous branches | Pogonarthria |
77. Inflorescences with 2-120 straight, non-disarticulating branches. | → 78 |
78. Spikelets with (2)3-12(20) bisexual florets | Leptochloa |
78. Spikelets with 2-4 florets, but only the lowest 1(2) florets bisexual | Gymnopogon |
74. Spikelets with 1 bisexual floret, sometimes with sterile, rudimentary, or modified florets distal to the bisexual floret. | → 79 |
79. Functional spikelets with sterile, rudimentary, or modified florets distal to the bisexual floret. | → 80 |
80. Spikelets widely spaced to slightly imbricate, appressed to the branch axes | Gymnopogon |
80. Spikelets densely imbricate, varying from appressed to strongly divergent. | → 81 |
81. Inflorescence branches usually solitary at each node (sometimes only 1 per panicle); spikelets laterally compressed or terete | Bouteloua |
81. Inflorescence branches usually more than 1 at the lower nodes; spikelets dorsally compressed | Enteropogon |
79. Functional spikelets with only 1 floret, lacking sterile, rudimentary, or modified florets. | → 82 |
82. Spikelets distant to slightly imbricate, appressed to the branches; branches strongly divergent. | → 83 |
83. Blades with thick, white margins and a well-developed midrib | Schedonnardus |
83. Blades lacking both thick, white margins and well-developed midribs | Gymnopogon |
82. Spikelets clearly imbricate, appressed to strongly divergent; branches appressed to strongly divergent. | → 84 |
84. Spikelets laterally compressed, appressed to divergent | Spartina |
84. Spikelets dorsally compressed, appressed | Willkommia |
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