Asteraceae tribe Astereae

Annuals, biennials, perennials, subshrubs, shrubs, or trees. Leaves usually cauline, sometimes mostly basal; alternate [opposite, whorled]; usually petiolate, sometimes sessile; margins entire or dentate to pinnatifid (often gland-dotted, especially in xerophytes). Heads homogamous (discoid; unisexual in Baccharis) or heterogamous (disciform or radiate), usually in corymbiform, paniculiform, racemiform, or spiciform arrays, sometimes borne singly. Calyculi 0. Phyllaries persistent or falling, usually in 3–5+ series (usually in spirals, sometimes in vertical ranks), distinct, unequal, and herbaceous to chartaceous or scarious or margins and/or apices notably scarious, sometimes in 1–2 series, distinct, subequal, and herbaceous with margins and/or apices barely to notably scarious. Receptacles usually flat to conic, sometimes concave, usually epaleate, rarely paleate (often foveolate, socket margins often fimbrillate; paleate in Eastwoodia and Rigiopappus). Ray florets 0 or in 1(–2+) series, usually pistillate, rarely neuter or styliferous and sterile; corollas usually yellow, cyanic, or white (laminae sometimes very reduced, e.g., Conyza spp.). Peripheral (pistillate) florets 0 or (in disciform heads) in 1–3+ series; corollas usually present, usually yellow, sometimes white, ochroleucous, or reddish to cyanic. Disc (inner) florets usually bisexual and fertile, rarely functionally staminate (e.g., Benitoa); corollas usually yellow, sometimes white, ochroleucous, or cyanic, actinomorphic, not 2-lipped, lobes (4–)5; anther bases obtuse or rounded, not tailed, apical appendages usually triangular to linear, sometimes none; styles abaxially glabrous and smooth or papillate (distally), branches ± linear, adaxially stigmatic in 2 lines from bases to apices or appendages, appendages usually deltate to lanceolate (abaxially papillate to hispidulous, adaxially smooth, glabrous). Cypselae monomorphic or dimorphic within heads, usually ± columnar to prismatic and 5-ribbed, sometimes compressed and 2-ribbed, rarely beaked, bodies smooth, muricate, ribbed, or rugulose (glabrous or hairy, hairs often glandular); pappi (rarely 0) usually persistent, usually of barbellulate to barbellate bristles in (1–)2–3+ series, sometimes of scales (scales sometimes aristate), rarely of both scales and bristles or of awns.

Distribution

Almost worldwide, mostly temperate.

Discussion

Genera 170, species 2800+ (77 genera, 719 species in the flora).

The classification and phylogeny of tribe Astereae has been the object of recent work, both morphologic (K. Bremer 1994; G. L. Nesom 1994, 2000) and molecular (notably the seminal paper by R. D. Noyes and L. H. Rieseberg 1999). Noyes and Rieseberg showed that most genera present in North America belong to a single monophyletic clade, called the North American clade. A series of subsequent studies done in various generic groups or subtribes led to a redefinition of many genera (see literature cited in each genus) and to the transfer of species between genera. The current treatment of the tribe reflects much of these novelties, many presented in a floristic work for the first time. Nesom and H. Robinson (unpubl.) present a worldwide overview of the classification of the tribe.

Large genera such as Erigeron, Symphyotrichum, and Solidago all originated on the continent and subsequently spread to Eurasia or South America. A few genera entered North America from neighboring continents, such as Aster in the strict sense (from Eurasia) or Baccharis (from Central America). A majority of Astereae genera in the flora of North America are endemic to the continent (more so if Mexico were included).

The generic order of the present treatment attempts to reflect the phylogenetic relationships established in recent molecular phylogenetic work.

Selected References

Anderson, L. C. and J. B. Creech. 1975. Comparative leaf anatomy of Solidago and related Asteraceae. Amer. J. Bot. 62: 486–493.

Beck, J. B. et al. 2004. Is subtribe Solidagininae (Asteraceae) monophyletic? Taxon 53: 691–698.

Brouillet, L., L. E. Urbatsch, and R. P. Roberts. 2004. Tonestus kingii and T. aberrans are related to Eurybia and the Machaerantherinae (Asteraceae: Astereae) based on nrDNA (ITS and ETS) data: Reinstatement of Herrickia and a new genus, Triniteurybia. Sida 21: 889–900.

Cronquist, A. and D. D. Keck. 1957. A reconstitution of the genus Machaeranthera. Brittonia 9: 231–239.

Fiz, O., V. Valcárcel, and P. Vargas. 2002. Phylogenetic position of Mediterranean Astereae and character evolution of daisies (Bellis, Asteraceae) inferred from nrDNA ITS sequences. Molec. Phylogen. Evol. 25: 157–171.

Hall, H. M. 1928. The genus Haplopappus: A phylogenetic study in the Compositae. Publ. Carnegie Inst. Wash. 389.

Hartman, R. L. 1976. A Conspectus of Machaeranthera (Compositae: Astereae) and a Biosystematic Study of the Section Blepharodon. Ph.D. dissertation. University of Texas.

Hartman, R. L. 1990. A conspectus of Machaeranthera (Asteraceae: Astereae). Phytologia 68: 439–465.

Jones, A. G. 1980. A classification of New World species of Aster (Asteraceae). Brittonia 32: 230–239.

Jones, A. G. and D. A. Young. 1983. Generic concepts of Aster (Asteraceae): A comparison of cladistic, phenetic and cytological approaches. Syst. Bot. 8: 71–84.

Kapoor, B. M. and J. R. Beaudry. 1966. Studies on Solidago. VII. The taxonomic status of the taxa Brachychaeta, Brintonia, Chrysoma, Euthamia, Oligoneuron, and Petradoria in relation to Solidago. Canad. J. Genet. Cytol. 8: 422–443.

Lane, M. A. 1982. Generic limits of Xanthocephalum, Gutierrezia, Amphiachyris, Gymnosperma, Greenella, and Thurovia. (Compositae: Astereae). Syst. Bot. 7: 405–416.

Lane, M. A. et al. 1996. Relationships of North American genera of Astereae, based on chloroplast DNA restriction site data. In: D. J. N. Hind et al., eds. 1996. Proceedings of the International Compositae Conference, Kew, 1994. 2 vols. Kew. Vol. 1, pp. 49–77.

Morgan, D. R. and B. B. Simpson. 1992. A systematic study of Machaeranthera (Asteraceae) and related groups using restriction site analysis of chloroplast DNA. Syst. Bot. 17: 511–531.

Morgan, D. R. 1997. Reticulate evolution in Machaeranthera (Asteraceae). Syst. Bot. 22: 599–615.

Morgan, D. R. 2003. nrDNA external transcribed spacer (ETS) sequence data, reticulate evolution, and the systematics of Machaeranthera (Asteraceae). Syst. Bot. 28: 179–190.

Morgan, D. R. and R. L. Hartman. 2003. A synopsis of Machaeranthera (Asteraceae: Astereae), with recognition of segregate genera. Sida 20: 1837–1416.

Nesom, G. L. 1991b. A phylogenetic hypothesis for the goldenasters (Asteraceae: Astereae). Phytologia 71: 136–151.

Nesom, G. L. 1993b. Taxonomic infrastructure of Solidago and Oligoneuron (Asteraceae: Astereae) and observations on their phylogenetic position. Phytologia 75: 1–44.

Nesom, G. L. 1994. Subtribal classification of the Astereae (Asteraceae). Phytologia 76: 193–274.

Nesom, G. L. 1994b. Review of the taxonomy of Aster sensu lato (Asteraceae: Astereae), emphasizing the New World species. Phytologia 77: 141–297.

Nesom, G. L. 1997. Taxonomic adjustments in North American Aster sensu latissimo (Asteraceae: Astereae). Phytologia 82: 281–288.

Nesom, G. L. 2000. Generic Conspectus of the Tribe Astereae (Asteraceae) in North America, Central America, the Antilles, and Hawaii. Fort Worth. [Sida Bot. Misc. 20.]

Noyes, R. D. and L. H. Rieseberg. 1999. ITS sequence data support a single origin for North American Astereae (Asteraceae) and reflect deep geographic divisions in Aster s.l. Amer. J. Bot. 86: 398–412.

Noyes, R. D. 2000. Biogeographical and evolutionary insights on Erigeron and allies (Asteraceae) from ITS sequence data. Pl. Syst. Evol. 220: 93–114.

Ruffin, J. 1974. A taxonomic evaluation of the genera Amphiachyris, Amphipappus, Greenella, Gutierrezia, Gymnosperma, Thurovia, and Xanthocephalum (Compositae). Sida 5: 301–333.

Ruffin, J. 1977. Palynological survey of the genera Amphiachyris, Amphipappus, Greenella, Gutierrezia, Gymnosperma, and Xanthocephalum (Compositae). Contr. Gray Herb. 207: 117–131.

Semple, J. C. and L. Brouillet. 1980. A synopsis of North American asters: The subgenera, sections and subsections of Aster and Lasallea. Amer. J. Bot. 67: 1010–1026.

Semple, J. C., G. S. Ringius, and J. J. Zhang. 1999. The Goldenrods of Ontario: Solidago L. and Euthamia Nutt., ed. 3. Waterloo. [Univ. Waterloo Biol. Ser. 39.]

Semple, J. C. and L. Tebby. 1999. A cladistic analysis of subtribe Chrysopsidinae (Asteraceae: Astereae). In: International Botanical Congress. [1999.] Abstracts. XVI International Botanical Congress, St. Louis, USA, August 1–7, 1999. [St. Louis.] Abstr. 2852, poster 401.

Semple, J. C., S. B. Heard, and L. Brouillet. 2002. Cultivated and Native Asters of Ontario (Compositae: Astereae). Aster L. (Including Asteromoea Blume, Diplactis Raf. and Kalimeris (Cass.) Cass.), Callistephus Cass., Galatella Cass., Doellingeria Nees, Oclemena E. L. Greene, Eurybia (Cass.) S. F. Gray, Canadanthus Nesom, and Symphyotrichum Nees (Including Virgulus Raf.). Waterloo. [Univ. Waterloo Biol. Ser. 41.]

Semple, J. C. and J. L. A. Hood. 2005. Pappus variation in North American Asters. I. Double, triple and quadruple pappus in Symphyotrichum and related aster genera (Asteraceae: Astereae). Sida 21: 2141–2159.

Solbrig, O. T. 1960. The status of the genera Amphiachyris, Amphipappus, Greenella, Gutierrezia, Gymnosperma, and Xanthocephalum (Compositae). Rhodora 62: 43–53.

Suh, Y. and B. B. Simpson. 1990. Phylogenetic analysis of chloroplast DNA in North American Gutierrezia and related genera (Asteraceae: Astereae). Syst. Bot. 660–670.

Turner, B. L. 1987b. Taxonomic study of Machaeranthera, sections Machaeranthera and Hesperastrum (Asteraceae). Phytologia 62: 207–266.

Urbatsch, L. E., R. P. Roberts, and V. Karaman. 2003. Phylogenetic evaluation of Xylothamia, Gundlachia, and related genera (Asteraceae, Astereae) based on ETS and ITS nrDNA sequence data. Amer. J. Bot. 90: 634–649.

Xiang, C. and J. C. Semple. 1996. Molecular systematic study of Aster sensu lato and related genera (Asteraceae: Astereae) based on chloroplast DNA restriction site analyses and mainly North American taxa. In: D. J. N. Hind et al., eds. 1996. Proceedings of the International Compositae Conference, Kew, 1994. 2 vols. Kew. Vol. 1, pp. 393–423.

Zanowiak, D. J. 1991. An Analysis of Systematic and Phyletic Relationships within Baccharidinae (Asteraceae: Astereae). Ph.D. dissertation. Texas A&M University.

Zhang, J. J. 1996. A Molecular Biosystematic Study on North American Solidago and Related Genera (Asteraceae: Astereae) Based on Chloroplast DNA RFLP Analysis (Phylogenetics). Ph.D. dissertation. University of Waterloo.

Lower Taxa

Acamptopappus, Almutaster, Ampelaster, Amphiachyris, Amphipappus, Aphanostephus, Arida, Aster, Astranthium, Baccharis, Bellis, Benitoa, Bigelowia, Boltonia, Bradburia, Brintonia, Canadanthus, Chaetopappa, Chloracantha, Chrysoma, Chrysopsis, Chrysothamnus, Columbiadoria, Conyza, Corethrogyne, Croptilon, Cuniculotinus, Dichaetophora, Dieteria, Doellingeria, Eastwoodia, Egletes, Ericameria, Erigeron, Eucephalus, Eurybia, Euthamia, Grindelia, Gundlachia, Gutierrezia, Gymnosperma, Hazardia, Herrickia, Heterotheca, Ionactis, Isocoma, Laënnecia, Lessingia, Lorandersonia, Machaeranthera, Monoptilon, Neonesomia, Nestotus, Oclemena, Oreochrysum, Oreostemma, Oönopsis, Pentachaeta, Petradoria, Pityopsis, Psilactis, Pyrrocoma, Rayjacksonia, Rigiopappus, Sericocarpus, Solidago, Stenotus, Symphyotrichum, Thurovia, Toiyabea, Tonestus, Townsendia, Tracyina, Triniteurybia, Xanthisma, Xanthocephalum, Xylorhiza

Keys

Key to Genera of Tribe Astereae

1	Trees, shrubs (sometimes clambering, sprawling, or vinelike), or subshrubs	Key A
1	Annuals, biennials, or perennials	> 2
2	Annuals or biennials	Key B
2	Perennials	Key C

Key A Trees, shrubs (sometimes clambering, sprawling, or vinelike), or subshrubs

1	Phyllaries unequal and disposed in vertical ranks	> 2
1	Phyllaries equal or unequal and disposed in spirals	> 7
2	Heads radiate	> 3
2	Heads discoid	> 4
3	Leaves cauline, blades 1-nerved (sometimes with 1–2 fainter lateral pairs)	Chrysoma
3	Leaves basal and cauline, blades 3–5-nerved (veins raised, parallel)	Petradoria
4	Leaves basal and cauline, blades 3-nerved; heads in glomerate clusters grouped in flat-topped, corymbiform arrays; phyllaries yellowish, sometimes green distally	Bigelowia
4	Leaves cauline, blades 1-nerved (sometimes with 1–2 fainter lateral pairs); heads (sometimes clustered) in paniculiform, corymbiform, or cymiform arrays, or borne singly; phyllaries stramineous, tan, or green, green or purplish distally	> 5
5	Leaf faces gland-dotted (in pits); heads in dense, cymiform arrays	Chrysoma
5	Leaf faces gland-dotted (sessile) or stipitate-glandular; heads borne singly or in condensed, cymiform clusters, grouped in paniculiform or corymbiform arrays, or in congested, cymiform to corymbiform arrays	> 6
6	Heads in congested, cymiform to corymbiform arrays; disc florets 4–15; cypselae oblong to obconic	Lorandersonia
6	Heads borne singly or in condensed, cymiform clusters grouped in paniculiform or corymbiform arrays; disc florets (2–)5–6(–40); cypselae subcylindric	Chrysothamnus
7	Trees, shrubs (sometimes clambering, sprawling, or vinelike)	> 8
7	Subshrubs	> 19
8	Plants unisexual, often glutinous; heads discoid	Baccharis
8	Plants bisexual, sometimes glutinous, gland-dotted, or stipitate-glandular; heads radiate, discoid, or disciform	> 9
9	Heads discoid or disciform	> 10
9	Heads radiate	> 14
10	Heads disciform (pistillate florets 4–9), in compact glomerules grouped in terminal corymbiform arrays; disc corollas orange-yellow; pappi 0, or minute crowns	Gymnosperma
10	Heads discoid, borne singly, or in clusters grouped in cymiform or racemiform arrays, or in cymiform, spiciform, racemiform, paniculiform, or corymbiform arrays; disc corollas yellow or white; pappi of scales or bristles	> 11
11	Cypselae 3–4-angled, strigoso-sericeous; pappi of (5–8) linear-lanceolate scales	Eastwoodia
11	Cypselae prismatic, terete, subterete, or compressed, glabrous or ± densely hairy; pappi of bristles	> 12
12	Stems not resinous; leaves entire or toothed (teeth sometimes bristly); heads usually in spiciform, racemiform, narrowly paniculiform, or corymbiform arrays, rarely borne singly;phyllaries not resinous; pappi reddish brown	Hazardia
12	Stems resinous; leaves entire; heads borne singly or in clusters (at branch tips), and/or in usually cymiform or racemiform, sometimes paniculiform or thyrsiform arrays; phyllaries resinous; pappi whitish tan to reddish	> 13
13	Leaves filiform, linear, lanceolate, or spatulate (adaxially sulcate, concave or plane), margins sometimes undulate or crisped; heads borne singly or in usually cymiform or racemiform, sometimes paniculiform or thyrsiform arrays; involucres hemispheric or obconic; disc florets 4–70, corolla lobes equal (cypselae 2–10 mm)	Ericameria
13	Leaves filiform, margins flat or involute; heads in clusters at branch tips, grouped in cymiform or racemiform arrays; involucres turbinate; disc florets 3–7, corolla lobes unequal (cypselae 1–3 mm)	Gundlachia
14	Shrubs clambering, sprawling, or vinelike; rays pale rose-purple to pale pink (Atlantic coastal plain)	Ampelaster
14	Shrubs not clambering, sprawling, or vinelike; rays yellow or white	> 15
15	Plants spinescent (at least with age); corollas yellow	> 16
15	Plants not spinescent; corollas white or yellow	> 17
16	Leaves sometimes in axillary fascicles; heads borne singly or in loose, corymbiform arrays; ray florets 5–14; disc florets 13–80, bisexual, fertile; pappi of barbellate scales	Acamptopappus
16	Leaves not in axillary fascicles; heads (2–4) in glomerate clusters, these grouped in corymbiform arrays; ray florets 1–2; disc florets 3–7, functionally staminate; pappi of flattened bristles (those of discs sometimes undulate to twisted)	Amphipappus
17	Leaves entire or toothed (teeth sometimes bristly; bases clasping or subclasping); heads usually in racemiform, narrowly paniculiform, or corymbiform arrays, rarely borne singly; phyllaries in 5–9 series; cypselae fusiform to deltoid, 4–5-nerved; pappi reddish brown	Hazardia
17	Leaves entire (bases not clasping); heads borne singly or in cymiform or racemiform (sometimes paniculiform or thyrsiform) arrays; phyllaries in 3–6+ series; cypselae ellipsoid to obconic or obovoid, ± 5–12-ribbed or -nerved; pappi whitish tan to reddish	> 18
18	Involucres hemispheric, obconic, or cylindric; disc corolla lobes equal; cypselae prismatic	Ericameria
18	Involucres turbinate; disc corolla lobes unequal; cypselae± turbinate	Neonesomia
19	Plants unisexual; heads discoid	Baccharis
19	Plants bisexual; heads radiate, disciform, or discoid	> 20
20	Heads disciform or discoid	> 21
20	Heads radiate	> 26
21	Stems eglandular; leaves entire	> 22
21	Stems gland-dotted or stipitate-glandular; leaves entire, toothed, or pinnatifid	> 23
22	Heads borne singly or in cymiform-racemiform arrays; involucres 11–15(–17) mm; florets 4–7; cypselae oblong, 5–6-ribbed, glabrous	Cuniculotinus
22	Heads borne singly in cymiform arrays; involucres 5–7 mm; florets 12–25+; cypselae narrowly oblong, 8–13-nerved (per face), ± sericeous	Arida
23	Heads borne singly (at tips of branches) or in corymbiform arrays; cypselae dimorphic (ray ± 3-sided, disc compressed)	Xanthisma
23	Heads usually in spiciform, racemiform, corymbiform, or cymiform arrays, rarely borne singly; cypselae monomorphic (terete, subterete, or compresssed)	> 24
24	Involucres broadly urceolate to hemispheric or globose; phyllaries usually looped to hooked, usually resinous	Grindelia
24	Involucres campanulate, obconic, turbinate, or cylindric; phyllaries not hooped or hooked, not resinous	> 25
25	Basal leaves persistent; heads in compact clusters grouped in corymbiform arrays; involucres 3–9.5 mm; disc corollas goblet-shaped (tubes elongating, elevating throats above involucres at flowering); cypselae obpyramidal, 5–11-ribbed (ribs sometimes thick and resinous), sericeous	Isocoma
25	Basal leaves withering by flowering; heads in spiciform, racemiform, or cymiform arrays; involucres 11–13 mm; disc corollas ± tubular (tubes not elevating throats); cypselae fusiform to deltoid, 4–5-nerved, glabrous	Hazardia
26	Rays white, light blue, or purple	> 27
26	Rays yellow (sometimes drying red-purple)	> 32
27	Plants often thorny (thorns green); leaves usually entire, rarely 1–2-denticulate; heads borne singly or in loose, corymbo-paniculiform arrays; involucres 4.5–7.5 mm; rays white; disc corolla veins orange, resinous	Chloracantha
27	Plants not thorny; leaves entire, dentate or serrate (teeth spinulose); heads borne singly or in corymbiform arrays; involucres 6–20 mm; rays white, light blue, or purple; disc corolla veins not orange-resinous	> 28
28	Cypselae 7–10-nerved, glabrous (Animas River Basin, n New Mexico,s Colorado)	Herrickia
28	Cypselae 2–7-nerved or -ribbed, hairy	> 29
29	Cypselae dimorphic (ray 3-sided, disc compressed), obovoid or oblong	Xanthisma
29	Cypselae monomorphic (compressed or terete), ovoid, fusiform, cuneiform, or linear	> 30
30	Cypselae flattened, 2–(3–4)-nerved; pappi of outer, shorter bristles orscales plus inner, longer bristles	Ionactis
30	Cypselae ± compressed or not, 4–7-ribbed; pappi of ± unequal bristles (outer not in notably distinct series)	> 31
31	Stems glabrous or villous to tomentose, sometimes stipitate-glandular; phyllaries keeled; ray florets bisexual, fertile; cypselae ovoid, fusiform, or linear, 4-nerved, sericeous	Xylorhiza
31	Stems usually densely white-tomentose, sometimes glabrate or ± stipitate-glandular distally; phyllaries flat; ray florets neuter; cypselae cuneiform or linear, 5–7-ribbed, puberulent to pilose	Corethrogyne
32	Phyllaries in vertical ranks; heads congested or glomerate, usually in corymbiform or cymiform, sometimes spiciform, arrays	> 33
32	Phyllaries in spirals; heads borne singly, 3–6, or glomerate, in flat-topped or multi-storied, corymbiform arrays, or in ± loose corymbiform, racemiform, narrowly paniculiform, or spiciform arrays	> 34
33	Leaves basal and cauline (not crowded), 3–5-nerved (veins parallel, raised); heads in glomerules in corymbiform arrays; ray florets 1–3; disc florets functionally staminate, corolla lobes lanceolate; cypselae cylindric, plump orslightly compressed	Petradoria
33	Leaves cauline (often crowded), usually 1-nerved, sometimes with 1–2 collateral pairs; heads in congested cymiform or corymbiform arrays; ray florets (1–)6–8; disc florets bisexual, fertile; cypselae oblong to obconic or prismatic	Lorandersonia
34	Involucres usually broadly urceolate, globose, or hemispheric; phyllaries filiform to linear, apices often looped or hooked, faces usually ± resinous	Grindelia
34	Involucres cylindro-turbinate, turbinate, obconic, campanulate, or hemispheric; phyllaries ovate, lanceolate, oblanceolate, or lanceolate to linear, apices straight or recurved (not looped or hooked), faces sometimes gland-dotted (not resinous).	> 35
35	Basal leaves pinnatifid (lobes bristle-tipped); pappi of setiform scales (or basally flattened bristles)	Xanthisma
35	Basal leaves not pinnatifid; pappi of bristles and/or scales	> 36
36	Pappi of scales	Gutierrezia
36	Pappi of bristles, or of outer, shorter scales plus inner, longer bristles	> 37
37	Stems prostrate to erect, mat-forming, branched; leaves cauline (crowded); heads borne singly	Nestotus
37	Stems erect, not mat-forming, branched or simple; leaves basal and cauline or mostly cauline (then not crowded); heads in spiciform, racemiform, corymbiform, or cymiform arrays, or glomerate and/or pedunculate-solitary in flat-topped or multi-storied, corymbiform arrays	> 38
38	Plants rhizomatous; heads usually glomerate, sometimes pedunculate-solitary, in flat-topped or multi-storied, corymbiform arrays	Euthamia
38	Plants taprooted or fibrous-rooted; heads not glomerate, in spiciform, racemiform, corymbiform, subumbelliform, paniculiform, or cymiform arrays	> 39
39	Leaves densely short-woolly (hairs flagelliform); heads in subumbelliform to paniculiform arrays; pappi of outer, triangular scales plus inner bristles in (2–)3 series; e North America	Chrysopsis
39	Leaves glabrous, sparsely puberulent or stipitate-glandular, or scabroso-hispidulous (hairs not flagelliform); heads in spiciform, racemiform, corymbiform, or cymiform arrays, sometimes borne singly; pappi of unequal bristles in 1–4 series; w North America	> 40
40	Leaves basal and cauline, margins entire; involucres cylindro-turbinate; ray florets 5–8; cypselae narrowly oblong, 8-nerved, moderately strigose	Columbiadoria
40	Leaves mostly cauline, margins serrate (teeth bristle-tipped); involucres campanulate; ray florets 5–18; cypselae fusiform to deltoid, 4–5-nerved, glabrous	Hazardia

Key B Annuals or biennials

1	Heads discoid or disciform (sometimes radiant)	> 2
1	Heads radiate	> 11
2	Heads discoid	> 3
2	Heads disciform	> 7
3	Pappi of (1–)2–10 setiform to subulate scales	> 4
3	Pappi 0, or of 3–55 bristles	> 5
4	Plants eglandular; heads sessile or subsessile, in secund, spiciform arrays	Thurovia
4	Plants usually gland-dotted and/or vernicose; heads usually in corymbiform arrays, rarely borne singly	Grindelia
5	Plants (gracile) 2–14 cm; leaves (linear to filiform) entire; pappi 0, or of (3–)5 bristles or setiform scales	Pentachaeta
5	Plants (1–)2–100 cm; leaves entire, toothed, or pinnately lobed; pappi of 3–55 bristles	> 6
6	Leaf adaxial faces glabrous, puberulent, or canescent; involucres turbinate; phyllaries usually spreading to reflexed, rarely appressed; corollas yellow (limbs of peripheral florets not expanded); pappus bristles white to tawny, distinct	Dieteria
6	Leaf adaxial faces sparsely tomentose to woolly; involucres hemispheric, obconic, campanulate, or narrowly cylindric; phyllaries erect or recurved; corollas white, pink, lavender, or yellow (limbs of peripheral florets freqently palmately expanded, heads ± radiant); pappus bristles tan to reddish, distinct or connate	Lessingia
7	Annuals (eglandular); disc corollas without prominent orange veins, style appendages lanceolate or linear	> 8
7	Biennials or annuals (usually gland-dotted or stipitate-glandular, sometimes eglandular, in Conyza); disc corollas sometimes with prominent orange veins (Conyza, Erigeron), style appendages deltate	> 9
8	Heads borne singly; peripheral pistillate (or reduced ray) florets in 1 series; pappi 0, or of (3–)5 bristles or subulate scales (not surpassing corollas at flowering); grassy areas, chaparral, California	Pentachaeta
8	Heads in paniculiform arrays (borne singly in small plants); peripheral pistillate florets in 2+ series; pappi of (20–)25–40(–55) bristles (surpassing corollas at flowering); ± saline habitats, edges of ponds, irrigation ditches, salted road-sides, saltmarshes; Rocky Mountains eastward	Symphyotrichum
9	Biennials; stems ascending; heads borne singly (at ends of branches), disc corolla throats somewhat inflated, white-indurate; pappi of outer, shorter setae plus 15–20 inner, barbellate bristles	Erigeron
9	Annuals; stems erect; heads usually in corymbiform, paniculiform or racemiform arrays, rarely borne singly; disc corollas narrowly funnelform (throats neither inflated nor indurate); pappi of 10–30 barbellate bristles	> 10
10	Leaf faces often stipitate-glandular or gland-dotted; phyllaries lacking orange to brown midnerves; cypselae densely sericeous, ± strigillose, or glabrous, often stipitate-glandular and/or gland-dotted	Laënnecia
10	Leaf faces eglandular; phyllaries with orange to brownish midnerves; cypselae glabrous or strigillose, eglandular	Conyza
11	Rays usually yellow or orange, sometimes cream, whitish, or white	> 12
11	Rays white, pink, purple, or blue	> 25
12	Pappi usually 0, or coroniform, or of scales, rarely of relatively short bristles (Xanthocephalum)	> 13
12	Pappi of bristles, or of outer, shorter setae or scales plus inner, longer bristles, or of outer bristles plus inner, subulate to setiform scales	> 17
13	Stems and leaves eglandular; phyllaries subequal (± navicular, inner usually each ± enfolding floret); receptacles sparsely paleate between ray and disc florets (paleae resembling phyllaries); ray corollas yellowish, often tinged with red or purple (laminae inconspicuous); disc corolla lobes 2–4	Rigiopappus
13	Stems and leaves (at least partly) stipitate-glandular; phyllaries unequal (not navicular nor each enfolding floret); receptacles epaleate; ray corollas yellow to orange-yellow or occasionally suffused with red (laminae conspicuous); disc corolla lobes 5	> 14
14	Disc corollas abruptly ampliate, throats usually campanulate, sometimes funnelform	> 15
14	Disc corollas not abruptly ampliate, throats funnelform or cylindric	> 16
15	Cypselae terete or slightly compressed with rounded edges or 4–6-sided, without prominent nerves, glabrous or slightly strigose; pappi of rays 0, outer discs 0 or minute crowns, inner 0, or usually of scales, rarely bristles; Arizona, Texas	Xanthocephalum
15	Cypselae ± triquetrous, 3-nerved, sericeous; pappi of 2–8 subulate, barbellate scales; California	Benitoa
16	Leaves not glutinous; heads in paniculiform or corymbiform arrays; phyllaries glutinous; disc florets functionally staminate	Amphiachyris
16	Leaves glutinous; heads borne singly or in clusters of 3–6; phyllaries not glutinous; disc florets bisexual, fertile	Gutierrezia
17	Stems and leaves usually gland-dotted and/or resinous; involucres usually globose to hemispheric or broadly urceolate, sometimes campanulate or obconic; phyllaries hooked, looped, patent, recurved, straight, or incurved	Grindelia
17	Stems and leaves usually not resinous, sometimes gland-dotted or stipitate-glandular; involucres hemispheric, campanulate, turbinate, obconic, or cylindric; phyllaries appressed, spreading, reflexed, or recurved	> 18
18	Cypselae dimorphic (rays often ± 3-angled, discs ± compressed)	> 19
18	Cypselae monomorphic (all ± compressed or all ± 3-angled)	> 21
19	Biennials; stems strigose and/or hispid, stipitate-glandular; pappi of rays 0, of discs of outer scales plus 30–45 inner bristles	Heterotheca
19	Annuals or biennials; stems glabrous or hispid, gland-dotted or stipitate-glandular; pappi of basally flattened bristles (or setiform scales) in 2–4 series	> 20
20	Heads borne singly or in corymbiform arrays (peduncles not cobwebby); involucres 4–10 mm; disc corolla throats gradually ampliate, ± funnelform; style-branch appendages lanceolate	Xanthisma
20	Heads borne singly or (2–3) in paniculiform or subcorymbiform-cymiform arrays (peduncles often cobwebby); involucres 7–16 mm; disc corolla throats abruptly ampliate, funnelform; style-branch appendages deltate	Rayjacksonia
21	Stems glabrous or glabrate, eglandular; cauline leaves narrowly oblanceolate, linear, or filiform, margins entire, ciliate, faces glabrous or glabrate, eglandular; heads borne singly (at ends of branches); phyllaries not thickened or keeled; rays yellow and often reddish or purplish-tinged	> 22
21	Stems ± hispid, pilose, woolly or arachnose, sometimes glabrous, stipitate-glandular or eglandular; cauline leaves ovate, oblanceolate, elliptic, lanceolate, or linear, margins entire, serrate, or apically dentate, sometimes coarsely ciliate, faces usually hairy, sometimes glabrous, sometimes stipitate-glandular; heads borne singly or in corymbiform, subumbelliform, or paniculiform arrays; phyllaries thickened or keeled; ray florets yellow to yellow-orange	> 23
22	Involucres campanulate to turbinate; phyllaries equal or subequal; cypselae oblanceoloid, 3–5-nerved, not beaked; pappus bristles (3–)5–20 (usually in multiples of 5) in 1 series	Pentachaeta
22	Involucres ± cylindric to turbinate or obconic; phyllaries unequal; cypselae ± fusifom, 5-nerved, beaked; pappus bristles (12–)30–40 in (1–)2 series (outer shorter)	Tracyina
23	Biennials, stems arachnose to woolly or glabrous, often stipitate-glandular; heads in corymbiform, subumbelliform, or paniculiform arrays; pappus bristles relatively fine (mainly Florida, Atlantic coastal plain)	Chrysopsis
23	Annuals, stems sparsely hispid or pilose, sometimes stipitate-glandular; heads borne singly or in loose paniculiform arrays; pappus bristles relatively thick and rigid, outer sometimes scalelike	> 24
24	Leaves 1-nerved, faces hispido-pilose; involucres campanulate, 6–9 mm; phyllaries linear, sparsely stipitate-glandular; cypselae obconic, compressed, smooth or slightly ribbed; Gulf coastal plain, Mississippi embayment, adjacent lowlands	Bradburia
24	Leaves 3-nerved (nerves ± parallel), faces thin-arachnose (in minute, abaxial lacunae); involucres narrowly turbinate to subcylindric, 4–8 mm; phyllaries lanceolate to linear-lanceolate, eglandular; cypselae turbinate, terete to weakly angled, 6–14-nerved; sc United States, adjacent Mexico	Croptilon
25	Receptacles conic; pappi 0, or coroniform, or of scales	> 26
25	Receptacles flat to convex; pappi usually of bristles (sometimes only discs or rays), or of setiform scales, or of bristles plus scales, or toothed cups with 1 bristle, sometimes of scales, or coroniform, or 0	> 30
26	Leaves usually pinnatifid to dentate, sometimes entire; rays without midstripe abaxially; cypselae not or slightly compressed, glabrous or sparsely strigose (hairs not glochidiform); pappi cartilaginous crowns, or crowns of scales or setae, or 0	> 27
26	Leaves usually entire, sometimes dentate or lobed; rays usually with pink or purplish midstripe abaxially; cypselae strongly compressed or flattened, glabrous or hairy (hairs glochidiform); pappi usually of awns, scales, bristles, or 2-horned crowns, sometimes 0	> 28
27	Plants gland-dotted; cypselae oblong to narrowly obovoid, slightly compressed, 2-nerved, sometimes gland-dotted	Egletes
27	Plants eglandular; cypselae columnar to prismatic, usually 4-angled, 4–12-ribbed (ribs relatively thick), eglandular	Aphanostephus
28	Phyllaries in 4–6+ series, unequal; pappi of 12–35+ lanceolate or subulate to setiform scales	Townsendia
28	Phyllaries in 2(–3) series, subequal; pappi 0, or crowns of setae or scales, or of 2 long plus ring of shorter awns	> 29
29	Leaves spatulate-obovate (basal), narrower distally; cypsela margins ribbed; pappi 0, or crowns of setae or scales	Astranthium
29	Leaves oblanceolate; cypsela margins winglike; pappi of 2 long plususually ring of shorter awns	Dichaetophora
30	Disc corollas with orange-resinous veins	> 31
30	Disc corolla veins not orange-resinous	> 34
31	Heads borne singly; pappi crowns (sometimes each with 1 bristle) or of alternating scales and bristles	> 32
31	Heads usually in corymbiform or paniculiform arrays, sometimes borne singly; pappi of bristles, or of outer, shorter setae or scales plus inner, longer bristles	> 33
32	Phyllaries in 2–6 series, unequal; pappi hyaline crowns (nearly 0) oralternating bristles and scales	Chaetopappa
32	Phyllaries in 1(–2) series, equal; pappi toothed crowns plus 1 distallyplumose bristle, or of 1–12 bristles alternating with scales	Monoptilon
33	Disc corolla throats slightly indurate and inflated; pappi usually of outer setae or scales plus 10–30 inner bristles, sometimes 0	Erigeron
33	Disc corolla throats not indurate or inflated; pappi of 15–25+ bristles in 1 series	Conyza
34	Pappi of 12–35+ scales	Townsendia
34	Pappi of 5–80+ bristles or setiform scales	> 35
35	Pappus bristles usually 5, rarely 0	Pentachaeta
35	Pappus bristles or setiform scales usually 20–80+ (ray sometimes 0)	> 36
36	Stems glabrous or hairy in lines distally, sometimes stipitate-glandular distally; leaf margins entire, subserrate, serrate, or pinnately lobed; heads usually in paniculiform or corymbiform arrays, sometimes borne singly	> 37
36	Stems hairy or glabrous, sometimes stipitate-glandular; leaf margins entire, serrate, dentate, laciniate, lobed, or ± deeply 1–2-pinnatifid (teeth or lobes apiculate, bristly, or spiny); heads borne singly (at ends of branches) or in cymiform or corymbiform arrays	> 38
37	Stems distally stipitate-glandular; cauline leaf bases clasping to subclasping, margins entire, coarsely toothed, or pinnately lobed, faces appressed-hairy or glabrous (distal stipitate-glandular); heads in corymbiform arrays; involucres broadly turbinate to hemispheric; phyllaries herbaceous distally, stipitate-glandular; ray florets 20–70 in 1 series, corollas white, blue, or purple; pappi: rays 0, discs of bristles	Psilactis
37	Stems eglandular; cauline leaf bases attenuate, cuneate, or rounded, margins entire or serrulate, faces glabrous, eglandular; heads in paniculiform arrays; involucres cylindro-campanulate, cylindric, or turbinate; phyllaries with distinct green zones distally, eglandular; ray florets 16–54 in 1–3 series, or 90–110 in 4–5 series, corollas white, pink, or lavender; pappi of bristles	Symphyotrichum
38	Leaves deeply 1–2-pinnatifid, at least many lobes or teeth acute and bristly	Machaeranthera
38	Leaves entire or toothed or lobed, if 1–2-pinnatifid, teeth or lobes often rounded, sometimes apiculate, mostly not bristly	> 39
39	Plants hairy, sometimes stipitate-glandular; leaves entire or toothed; ray pappi of 40–50 bristles	Dieteria
39	Plants glabrous and leaves entire or toothed (ciliate or teeth bristle-tipped or apiculate), or plants hairy, sometimes stipitate-glandular, and leaves 1–2-pinnatifid; ray pappi usually 0 (if 20–30 bristles, leaves 1–2-pinnatifid)	Arida

Key C Perennials

1	Heads discoid or disciform	> 2
1	Heads radiate	> 18
2	Heads disciform	> 3
2	Heads discoid	> 5
3	Cauline leaf margins entire or spinulose-serrate; heads borne singly or 2–3 in ± corymbiform arrays; cypselae subcylindric-fusiform, 3–4-angled, ± compressed, with 10–12 faint nerves; pappi of 15–60 rigid, unequal, smooth bristles in 1 series	Pyrrocoma
3	Cauline leaf margins entire, dentate, or pinnatifid (lobed); heads in corymbiform arrays; cypselae oblong or oblong-obovoid to elliptic or obovoid, ± compressed or flattened, 2(–4)-nerved or ± nerved on edges; pappi of outer setae or scales plus 5–40 bristles, or of 30–40+ bristles in 2 series (outer usually shorter)	> 4
4	Plants ± densely white-tomentose (at least some surfaces); phyllaries 1-nerved, nerves not golden-resinous; disc corollas yellowish, throats narrowly funnelform, not indurate, veins light, not resinous; pappi of 30–40+ bristles in 2 series (outer usually shorter)	Laënnecia
4	Plants ± hirsute or pilose; phyllaries usually 1–3-nerved, nerves golden-resinous; disc corollas yellow, strongly constricted basally, throats sometimes strongly inflated-indurate, nerves often orange-resinous; pappi of outer setae (or 0) plus 7–25 inner bristles	Erigeron
5	Disc corollas white or pale yellow; pappi of 10 basally connate scales	Thurovia
5	Disc corollas yellow (white in Brintonia); pappi usually of distinct bristles or of outer, shorter setae or scales plus inner, longer bristles, sometimes 0	> 6
6	Stems and leaves resinous, gland-dotted; phyllary apices hooked or looped, or slightly recurved to straight; pappi of 2–8 bristles	Grindelia
6	Stems and leaves sometimes resinous, sometimes stipitate-glandular or gland-dotted; phyllary apices straight to squarrose; pappi of 10+ bristles	> 7
7	Phyllary midveins translucent and swollen at least basally (not resinous)	> 8
7	Phyllary midveins usually not notably swollen (orange-resinous in Erigeron)	> 9
8	Disc corollas white	Brintonia
8	Disc corollas yellow	Solidago
9	Phyllary and corolla nerves orange-resinous; pappi of outer, shorter setae or scales plus inner, longer bristles	Erigeron
9	Phyllary and corolla nerves not orange-resinous, or only corolla nerves orange-resinous; pappi of equal or unequal bristles.	> 10
10	Phyllaries subequal, foliaceous	Toiyabea
10	Phyllaries unequal (sometimes subequal, then outer not foliaceous), outer ± herbaceous (sometimes foliaceous), or chartaceous, or proximally indurate	> 11
11	Phyllaries keeled, distally only with relatively small green zones or green along midveins; pappus bristles in 2–3 series (outer in notably shorter series or relatively few)	> 12
11	Phyllaries usually flat, sometimes keeled, distally herbaceous or green; pappi of equal or unequal bristles in 1–3 series (outer not in notably shorter series)	> 13
12	Leaves cauline (proximal withering by flowering), margins without coarse spreading cilia near bases; phyllary margins often reddish, sometimes hyaline, abaxial faces glabrous or glabrate to woolly, sometimes stipitate-glandular	Eucephalus
12	Leaves basal and cauline (basal and proximal withering by flowering), margins with coarse spreading cilia near bases or on petioles; phyllary margins not reddish, scarious, abaxial faces ± hispid or stipitate-glandular	Heterotheca
13	Leaf faces densely scabrous and short-stipitate-glandular; phyllaries ± keeled proximally (Esmeralda County, Nevada)	Tonestus
13	Leaf faces glabrous or canescent, ± puberulent, hispidulous, tomentose, or villous, and/or sometimes ± stipitate-glandular or gland-dotted; phyllaries sometimes keeled	> 14
14	Leaves basal and cauline, basal and proximal petiolate, distal sessile; disc floret style appendages lanceolate	> 15
14	Leaves cauline, sessile; disc floret style appendages triangular	> 16
15	Plants densely stipitate-glandular, with caudices; stems densely clustered, simple; leaf blades obovate or oblong to broadly oblanceolate; phyllaries keeled; disc corolla throats cylindric; cypselae white strigoso-hirsute	Triniteurybia
15	Plants sparsely, if at all, stipitate-glandular, taprooted; stems single, usually branched; leaf blades lanceolate to oblanceolate; phyllaries flat; disc corolla throats funnelform; cypselae sparsely appressed-hairy	Dieteria
16	Phyllary margins scarious; disc corolla lobes unequal; cypselae obpyramidal, sericeous; pappi of 40–50 tawny bristles	Isocoma
16	Phyllary margins not scarious; disc corolla lobes equal; cypselae prismatic, narrowly turbinate, fusiform, or deltoid, glabrous or sparsely scabrous; pappi of 15–30 reddish brown to brownish bristles	> 17
17	Stems glabrous or scabrous, eglandular; leaf bases not subclasping, margins entire; cypselae prismatic or narrowly turbinate; pappus bristles barbellate	Oönopsis
17	Stems scabrous to sparsely tomentulose, distally stipitate-glandular; leaf bases subclasping, margins serrate; cypselae fusiform to deltoid; pappus bristles smooth	Hazardia
18	Rays usually yellow or orange, sometimes cream-colored or white	> 19
18	Rays white, pink, purple, or blue	> 38
19	Pappi 0, or crowns, or of scales	> 20
19	Pappi of bristles, or of outer shorter setae, bristles, or scales plus inner, longer bristles, or of setiform awns.	> 21
20	Leaves cauline (basal withering by flowering), blades linear to lanceolate or spatulate, stipitate-glandular; heads borne singly or in clusters of 3–6; phyllaries in 2–4 series; cypselae clavate or cylindric, not compresssed, 5–8-nerved, white-hairy (hairs clavate to bulbous); pappi usually of 5–10 scales, sometimes crowns or 0	Gutierrezia
20	Leaves basal (present at flowering) and cauline, blades spatulate, eglandular; heads borne singly (± sessile); phyllaries in 3–7+ series; cypselae obovoid to lanceoloid, flattened, 2-nerved, hairy (hairs glochidiform); pappi of 10–12 (ray) or 20–35+ (disc), lanceolate to subulate or setiform scales	Townsendia
21	Pappi of outer shorter setae, bristles, or scales plus inner, longer bristles in 2 series	> 22
21	Pappi of setiform scales or bristles in 1–4 series	> 26
22	Plants taprooted or with simple caudices (and fibrous-rooted); heads borne singly or in 2s or 3s; phyllaries in 2–3 series, equal or subequal, flat, usually 1–3-nerved (nerves golden-resinous); cypselae 2-nerved, not resinous	Erigeron
22	Plants taprooted, rhizomatous, or with branched caudices; heads in corymbiform, ± paniculiform, or subumbelliform arrays, sometimes borne singly; phyllaries in 3–5 series, unequal, usually thickened or keeled (not in Bradburia), 1-nerved, not golden-resinous; cypselae smooth or 1–14-nerved or -ribbed, nerves or ribs sometimes resinous	> 23
23	Stems and leaves silky-sericeous, rarely glabrate; leaves sessile, blades 3–11-parallel-nerved (nerves sunken), linear to lanceolate or ovate (often grasslike), margins entire; involucres turbinate	Pityopsis
23	Stems and leaves whitish-strigose, pilose, hispid, or arachnose to woolly (hairs flagelliform, soft), or glabrous; leaves sessile or basal petiolate, blades usually 1-nerved (veins reticulate, raised abaxially), spatulate, ovate-oblanceolate, ovate, elliptic, elliptic-oblong, oblanceolate, linear-lanceolate, or (usually distal) linear, margins entire, serrate, or dentate (sometimes coarsely ciliate); involucres campanulate or turbinate	> 24
24	Plants proximally woolly, distally arachnose or pilose (hairs flagelliform); basal leaves sessile	Chrysopsis
24	Plants sparsely to ± densely hispid, strigose, or pilose (hairs not flagelliform); basal leaves petiolate	> 25
25	Perennials (taproots relatively short and/or caudices woody); basal petioles ciliate; cauline leaves much reduced distally, not clasping; heads borne singly or in lax paniculiform arrays; cypselae monomorphic, ray pappi of outer, shorter, setiform scales or bristles plus inner, longer bristles	Bradburia
25	Perennials (caudices woody); basal petioles long-strigoso-ciliate; cauline leaves ± reduced distally, sometimes clasping or subclasping; heads borne singly or in corymbiform, sometimes paniculiform arrays; cypselae dimorphic or monomorphic, ray pappi 0, or of outer, linear-lanceolate scales plus inner, longer bristles	Heterotheca
26	Stems and leaves resinous, gland-dotted; involucres usually globose, hemispheric, or broadly urceolate, sometimes campanulate to obconic, usually ± resinous; pappi of (1–)2–8 white, straight, contorted, or curled, barbellate or smooth awns or setiform scales in 1 series	Grindelia
26	Stems and leaves usually not resinous, sometimes stipitate-glandular or gland-dotted; involucres hemispheric, campanulate, turbinate, or cylindric, not resinous, sometimes viscid or stipitate-glandular or gland-dotted; pappi of white, tawny, brownish, or reddish, barbellate bristles in 1–4 series	> 27
27	Plants ± colonial (rhizomatous); heads usually glomerate, and/or sometimes pedunculate-solitary in flat-topped or multi-storied, corymbiform arrays	Euthamia
27	Plants colonial (sometimes rhizomatous, stems single or clustered, usually from ± woody taproots or caudices); heads borne singly, or (2–5) in paniculiform to corymbiform arrays, or in open or dense corymbiform, paniculiform (diversely shaped in Solidago), racemiform, or spiciform arrays (if glomerate, not in flat-topped, corymbiform arrays, arrays not storied)	> 28
28	Plants rhizomatous (often colonial); heads in dense corymbiform or paniculiform arrays	> 29
28	Plants usually taprooted or with caudices, sometimes also from spreading roots (stems single or clustered); heads usually borne singly, sometimes (2–5) in loose corymbiform, cymiform, or paniculiform arrays, or in spiciform, racemiform, paniculiform, or corymbiform arrays, or glomerate (some Oönopsis)	> 30
29	Stems and leaves sometimes stipitate-glandular or gland-dotted; cauline leaf bases not clasping, faces sometimes resinous; heads in rounded, club-shaped, wand-shaped, or pyramid-shaped paniculiform (often secund) arrays, or in flat-topped, corymbiform arrays; involucres campanulate to cylindric, 3–12 mm, sometimes stipitate-glandular; phyllary midveins usually swollen, translucent, apices often with green zone, sometimes reflexed; ray florets 3–15(–21); disc corolla lobes lanceolate, erect to reflexed, style-branch appendages triangular; cypselae obconic, terete or ± compressed, 5–8-nerved; pappi of unequal bristles in 1–2(–3) series	Solidago
29	Stems and leaves stipitate-glandular; cauline leaf bases clasping or subclasping, faces resinous; heads in dense, flat-topped, corymbiform arrays; involucres campanulate to hemispheric, 10–11 mm, stipitate-glandular; phyllary midveins not swollen, apices green-tipped and spreading-reflexed; ray florets 12–20; disc corolla lobes triangular, spreading, style-branch appendages linear; cypselae fusiform, distinctly compressed, 12–16-nerved (nerves whitish, raised); pappi of equal bristles in 2(–3) series; w United States	Oreochrysum
30	Stems sometimes clustered; heads usually in rounded, club-shaped, wand-shaped, or pyramid-shaped, paniculiform, or flat-topped, corymbiform (often secund) arrays, or in spiciform, racemiform, or cymiform arrays, sometimes borne singly	> 31
30	Stems single or clustered; heads borne singly or (2–5) in loose, corymbiform or paniculiform arrays, or 2–5(–15) in racemiform, spiciform, or corymbiform arrays	> 32
31	Plants with caudices (stems clustered); leaves basal and cauline; heads in rounded, club-shaped, wand-shaped, or pyramid-shaped, paniculiform (often secund) or flat-topped corymbiform arrays; involucres campanulate to cylindric, 3–12 mm; phyllary midveins usually swollen and translucent; cypselae 5–8-nerved	Solidago
31	Plants taprooted; leaves mostly cauline; heads usually in spiciform, racemiform, or cymiform arrays, sometimes borne singly; involucres campanulate, 11–13 mm; phyllary midveins not swollen; cypselae 4–5-nerved (California, Oregon)	Hazardia
32	Stems single, usually branched; cypselae dimorphic (rays 3-angled, discs ± compressed), obovoid, oblong, or obscurely cordate, or rays broadly ellipsoid to obovoid (thick-walled) and discs broadly ellipsoid to clavate (thin-walled); pappi of coarse, barbellate bristles or setiform scales	> 33
32	Stems single or clustered, usually simple; cypselae monomorphic, terete or compressed to ± flattened, prismatic (3–4-angled), narrowly turbinate, subcylindric-fusiform, cylindric, or linear (usually thin-walled); pappi of relatively fine barbellate bristles	> 34
33	Basal leaves 1–2-pinnatifid, cauline deeply incised to coarsely dentate or ± entire; involucres 6–10 mm; phyllaries stiff, leathery or bases indurate, apices herbaceous; disc corolla throats not abruptly ampliate, style-branch append-ages lanceolate	Xanthisma
33	Leaves linear to oblanceolate, coarsely serrate to entire; involucres 7–16 mm; phyllaries herbaceous; disc corolla throats abruptly ampliate, style-branchappendages deltate	Rayjacksonia
34	Leaves 3-nerved, faces arachnose (in minute, abaxial lacunae); involucresnarrowly turbinate to subcylindric; pappi tawny to reddish brown	Croptilon
34	Leaves 1–3(–5)-nerved, faces glabrous, scabrous, villous, sericeous, tomentose, or lanate; involucres hemispheric to broadly or narrowly campanulate; pappi whitish or brownish	> 35
35	Plants sometimes mat-forming; stems clustered; leaves 1–5-nerved; margins of outer phyllaries scarious; pappi whitish	> 36
35	Plants not mat-forming; stems single or clustered; leaves 1-nerved; margins of outer phyllaries herbaceous (sometimes proximally indurate); pappi brownish	> 37
36	Stems eglandular or stipitate-glandular, sometimes resinous; leaf margins entire, faces glabrous, scabrous, villous, or lanate, usually stipitate-glandular, sometimes eglandular; phyllaries unequal, proximally indurate, distally chartaceous or herbaceous; ray florets 5–17; cypselae usually sericeous, sometimes glabrous	Stenotus
36	Stems densely stipitate-glandular (viscid); leaf margins entire, coarsely and irregularly serrate, dentate, or lobed, faces glabrous or scabrous, sometimes stipitate-glandular; phyllaries subequal, outer foliaceous; ray florets 11–23(–35); cypselae glabrous or villous	Tonestus
37	Stems and leaves glabrous or sparsely tomentose, eglandular; leaves basal (usually withering by flowering) and cauline, blades narrowly oblanceolate to lanceolate or linear, margins entire; heads borne singly, or 2–12 in glomerules or in loose, corymbiform arrays (subtended by little-reduced distal leaves); rays 6–25; cypselae prismatic or narrowly turbinate	Oönopsis
37	Stems and leaves loosely tomentose to woolly, sometimes gland-dotted or stipitate-glandular; leaves basal (persistent) and cauline, basal blades oblanceolate to elliptic or linear, cauline lanceolate, margins entire, spinulose-dentate or -serrate, or shallowly laciniate; heads borne singly or (2–15, ± sessile) in racemiform, spiciform, or loose, corymbiform arrays (at ends of scapiform stems or peduncles); rays 10–80; cypselae subcylindric-fusiform	Pyrrocoma
38	Receptacles conic; rays white (pink or purplish-tinged abaxially)	> 39
38	Receptacles flat or convex; rays white, pink, blue, or purple (not tinged abaxially)	> 40
39	Plants 5–20 cm (scapiform, short-rhizomatous); leaves mostly basal, margins crenate-serrate; phyllary margins herbaceous; rays in 3–4 series (closing at night); cypselae obconic, compressed, margins thickened, riblike, apices not cupped; pappi 0	Bellis
39	Plants 5–50 cm (leafy, taprooted); leaves basal and cauline, margins entire or toothed to pinnatifid; phyllary margins broadly scarious; rays in 1(–2) series (not closing at night); cypselae columnar, usually 4-angled, 4–12-ribbed, apices usually cupped; pappi of awns, aristate scales, short bristles, or 0	Aphanostephus
40	Plants colonial; stems branched (lateral branches strongly ascending, commonly modified to green thorns); leaves early withering; phyllaries (1–)3(–5)-nerved (usually wet sites in arid, sw United States)	Chloracantha
40	Plants sometimes colonial; stems single or clustered, simple or branched (not becoming thorny); at least distal leaves persistent through flowering; phyllaries usually 1-nerved, seldom 3-nerved	> 41
41	Cypselae usually obconic or obovoid, sometimes lanceoloid, flattened or compressed, margins ribbed (sometimes 1–2 nerves also on faces)	> 42
41	Cypseale ± narrowly obconic, obovoid, oblanceoloid, lanceoloid, fusiform, or linear, ± compressed or terete, sometimes winged or wings reduced and resembling marginal nerves or ribs (then pappi 0 or of minute scales), usually 3–12+-nerved on faces (margins not ribbed)	> 46
42	Leaves cauline; phyllaries keeled	> 43
42	Leaves basal and/or cauline; phyllaries not keeled	> 44
43	Plants 10–160 cm, minutely stipitate-glandular distally; proximalmost leaves scalelike, proximal withering by flowering, cauline distally increasing in size to mid stems, mid and distal blades lanceolate or lance-ovate to elliptic; heads in racemiform or corymbiform arrays; cypselae glabrous, pilose, or strigose, eglandular; pappi of outer, shorter plus inner, longer bristles in 3 series	Eucephalus
43	Plants 4–30(–70) cm, sometimes stipitate-glandular; leaves persistent to flowering, mostly equal in size and shape, blades spatulate (proximal), linear, narrowly oblong, or elliptic-lanceolate; heads borne singly or in 2s or 3s, or in corymbiform arrays; cypselae densely strigose or sericeous, sometimes stipitate-glandular; pappi of outer shorter bristles or scales plus inner, longer bristles in 2 series	Ionactis
44	Leaf faces eglandular; corolla lobes lanceolate; pappi of 20–30 bristles	Aster
44	Leaf faces often gland-dotted; corolla lobes deltate or lance-deltate; pappi usually of 12–35+ scales, or of outer setae or scales plus 5–40(–50) bristles (sometimes only on rays or on discs), sometimes 0	> 45
45	Plants taprooted or with branched caudices; heads borne singly; leaves usually entire, rarely toothed or lobed; phyllaries unequal, 1-nerved (nerves not golden-resinous); disc corolla throats funnelform; cypselae glabrous or hairy (hairs glochidiform); pappi of 12–35+ scales	Townsendia
45	Plants rhizomatous, sometimes taprooted; heads borne singly or in corymbiform arrays; leaves entire, ± dentate, or pin-natifid; phyllaries equal to unequal, 1–3-nerved (nerves golden-resinous); disc corolla throats sometimes strongly inflated-indurate; cypselae glabrous, strigose, or sericeous; pappi usually of outer, shorter setae or scales plus 5–40(–50) inner, longer bristles (sometimes only on rays or discs),sometimes 0	Erigeron
46	Pappi 0, or crowns of setae or scales, or of scales, of alternating scales and bristles, or of outer, shorter setae or scales plus inner, longer bristles	> 47
46	Pappi of bristles or setiform scales	> 50
47	Phyllary midnerves not swollen, not orange-resinous; disc style-branch appendages triangular or lanceolate	> 48
47	Phyllary midnerves (or 1–3 nerves) orange-resinous; disc style-branch appendages deltate	> 49
48	Leaves usually entire, sometimes dentate or lobed, bases clasping or subclasping; phyllaries subequal; pappi rings or crowns of setae or scales	Astranthium
48	Leaves entire, bases not clasping; phyllaries unequal; pappi thickened rings, crowns of scales (basally fused or distinct), or minute outer scales plus inner bristles	Chaetopappa
49	Plants not colonial (stems ± clustered), stems and leaves stipitate-glandular; basal leaves persistent or withering by flowering; heads borne singly or (2–10) in corymbiform arrays; pappi usually of outer setae or scales plus 5–40(–50) inner bristles, sometimes 0	Erigeron
49	Plants colonial, stems and leaves eglandular; basal leaves withering by flowering; heads in corymbiform or diffuse, paniculiform arrays; pappi of 2–3 awns plus shorter bristles or scales, or wholly of minute scales	Boltonia
50	Cypselae ± dimorphic (ray 3-sided and rounded abaxially, disc ± compressed); pappi of relatively coarse (± flattened) bristles or setiform scales	> 51
50	Cypselae monomorphic; pappi of relatively fine bristles	> 52
51	Stems simple; leaves mostly basal, margins serrate or serrulate; involucres depressed-hemispheric; cypselae 3–9-ribbed on each face; pappus bristles coarsely barbellate	Xanthisma
51	Stems usually branched; leaves basal (persistent in rosettes or withering) and cauline (distally ± reduced) or mostly cauline, margins pinnately lobed or pinnatifid, toothed, or entire; involucres turbinate, campanulate, or hemispheric; cypselae 8–13-nerved on each face; pappus bristles barbellulate	Arida
52	Plants mostly rhizomatous, sometimes with caudices; heads in paniculiform or racemiform arrays, rarely borne singly	> 53
52	Plants taprooted, with caudices, or rhizomatous; heads in corymbiform (or flat-topped racemiform) arrays or borne singly, or sometimes grouped into loose corymbiform arrays	> 56
53	Stems spreading-hirsute, eglandular; heads in narrow (wand-shaped), paniculiform arrays; phyllary midribs translucent and swollen; rays 7–9, corollas white to pale cream	Solidago
53	Stems usually glabrous, often distally hairy in lines, sometimes ± densely hairy, sometimes distally stipitate-glandular; heads in ± open or dense (not wand-shaped), paniculiform arrays; phyllary midnerves not translucent and swollen; rays (8–)12–65(–75), corollas white, pink, blue, or purple	> 54
54	Phyllaries usually unequal, sometimes subequal, proximally indurate, distally with defined green zone, sometimes distally foliaceous, or outer wholly foliaceous, sometimes short-stipitate-glandular	Symphyotrichum
54	Phyllaries subequal, herbaceous (without definite distal green zones, not foliaceous), short-stipitate-glandular	> 55
55	Stems ± densely villous; leaves cauline, blades 1-nerved (venation reticulate), lanceolate to elliptic, bases auriculate-clasping, abaxial faces glabrate to ± strigose, adaxial sparsely villous (distal stipitate-glandular); phyllaries often purplish, apices of outer acuminate; disc corollas whitish to pale yellow; cold wet soils, montane (n Cordilleras) and boreal North America	Canadanthus
55	Stems glabrous; leaves basal and cauline, blades 3-nerved (nerves ± parallel), linear, bases subclasping, faces glabrous (distal stipitate-glandular); phyllaries green, apices of outer acute; disc corollas yellow; damp alkaline areas, deserts and dry prairies, w North America	Almutaster
56	Plants usually tapooted, sometimes with caudices (also rhizomatous from fibrous roots in Chaetopappa); stems usually 1 (sometimes 2–5+ in clusters), branched or simple; heads borne singly or in loose corymbiform arrays	> 57
56	Plants rhizomatous or with caudices; stems 1–5+, usually simple; heads usually in corymbiform arrays, sometimes borne singly (then plants long-rhizomatous, rays pink)	> 62
57	Stems and leaves usually densely white-tomentose, sometimes glabrate, stipitate-glandular or gland-dotted; stems simple; ray florets neuter; cypselae cuneiform or linear; pappi reddish to brownish (bristles relatively coarse, California)	Corethrogyne
57	Stems and leaves glabrous, glabrate, canescent, villous, or tomentose, sometimes stipitate-glandular or gland-dotted; stems simple or branched; ray florets pistillate, fertile; cypselae fusiform, cylindric, obovoid, or linear; pappi hyaline or white to tawny	> 58
58	Stems simple; leaf margins entire; phyllaries mostly foliaceous (margins sometimes proximally indurate); rays white (maturing or drying bluish or purplish)	> 59
58	Stems branched or simple; leaf margins entire or toothed (teeth apiculate, ± spinulose, or spine-tipped); phyllaries usually not foliaceous (proximally white-indurate, distally green or herbaceous); rays white, blue, violet, or purple	> 60
59	Leaves basal and cauline (crowded), blades linear-oblanceolate to lanceolate, 1-nerved; phyllaries not keeled; cypselae 5-nerved	Chaetopappa
59	Leaves mostly basal (rosettes), blades linear to oblanceolate, 3-nerved; phyllaries often ± keeled; cypselae 5–10-nerved (nerves raised)	Oreostemma
60	Stems mostly simple (scapiform); leaves mostly basal (rosettes, often marcescent), margins entire or irregularly serrate (teeth apiculate or ± spinulose); phyllaries squarrose; cypselae 8–10-ribbed (canyons, rock faces, Utah)	Herrickia
60	Stems mostly branched; leaves basal and cauline, margins entire or toothed (teeth spinose-tipped); phyllaries appressed, spreading, or reflexed; cypselae 4-nerved, 4–6-ribbed, or smooth	> 61
61	Stems mostly single; cauline leaf blades lanceolate to oblanceolate; phyllaries not keeled	Dieteria
61	Stems clustered; cauline leaf blades spatulate to obovate oroblong, rarely elliptic; phyllaries keeled	Xylorhiza
62	Phyllaries flat, not keeled, midveins orange-resinous or swollen and translucent	> 63
62	Phyllaries ± rounded, sometimes ± keeled, midveins not swollen	> 64
63	Plants 40–200 cm; leaves basal (not persistent, reduced) and cauline, blades 1-nerved (venation brochidodromous), lanceolate to elliptic; phyllary midveins orange-resinous; rays 2–10(–16)	Doellingeria
63	Plants 10–40 cm; leaves basal (persistent, well developed) and cauline (reduced), blades usually 1-nerved, sometimes ± 3-nerved (venation reticulate), linear to linear-lanceolate, phyllary midveins swollen, translucent; ray florets 10–20	Solidago
64	Plants rhizomatous and/or with woody caudices (rhizomes with swollen apical buds); heads in ± loose, corymbiform arrays or borne singly (nodding in bud); phyllaries lance-ovate to linear (membranous), proximally not indurate, green along midnerves; cypselae 5–8-nerved (lateral 2 thicker), glabrous, ± densely gland-dotted; e North America	Oclemena
64	Plants rhizomatous (rhizomes not apically swollen) and/or with caudices; heads in corymbiform arrays (erect in bud); phyllaries ovate, oblong, lanceolate, or linear-lanceolate, proximally indurate, distally with sharply delimited green apical zones; cypselae 7–12(–18)-nerved, glabrous, strigillose, or strigose, eglandular; e, w North America (excluding United States prairies)	> 65
65	Involucres cylindric; ray florets 1–6, white; disc corollas white or cream-colored; cypselae ± densely strigose	Sericocarpus
65	Involucres cylindro-campanulate or campanulate; rays 5–60, white to purple; disc corollas yellow; cypselae glabrous or ± densely strigillose	> 66
66	Stems and leaves usually stipitate-glandular, sometimes eglandular and glaucous; leaves mostly cauline, entire or spinulose-serrate, glabrous or scabrellous; phyllaries sometimes rounded, usually keeled, apices acuteto long-acuminate; rays 8–27; disc corolla tubes shorter than limbs (w Cordilleras)	Herrickia
66	Stems and leaves usually eglandular, sometimes stipitate-glandular (e North America only), not glaucous; leaves basal and/or cauline, serrate (teeth sometimes spinulose or spinose, blades then linear, grasslike, se North America) or entire, hairy or glabrous; phyllaries usually rounded, sometimes keeled, apices obtuse to acute; rays 5–60; disc corolla tubes shorter or longer than limbs	Eurybia