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FNA | Family List | FNA Vol. 20 | Asteraceae

187k. Asteraceae Martinov tribe Astereae Cassini, J. Phys. Chim. Hist. Nat. Arts. 88: 195. 1819.

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.

Genera 170, species 2800+ (77 genera, 719 species in the flora): almost worldwide, mostly temperate.

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.


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

Key C Perennials

1 Heads discoid or disciform   (2)
+ Heads radiate   (18)
2 (1) Heads disciform   (3)
+ Heads discoid   (5)
3 (2) 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   201 Pyrrocoma (in part), p. 413
+ 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 (3) 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)   142 Laënnecia (in part), p. 36
+ 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   186 Erigeron (in part), p. 256
5 (2) Disc corollas white or pale yellow; pappi of 10 basally connate scales   153 Thurovia (in part), p. 86
+ 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 (5) Stems and leaves resinous, gland-dotted; phyllary apices hooked or looped, or slightly recurved to straight; pappi of 2–8 bristles   202 Grindelia (in part), p. 424
+ Stems and leaves sometimes resinous, sometimes stipitate-glandular or gland-dotted; phyllary apices straight to squarrose; pappi of 10+ bristles   (7)
7 (6) Phyllary midveins translucent and swollen at least basally (not resinous)   (8)
+ Phyllary midveins usually not notably swollen (orange-resinous in Erigeron)   (9)
8 (7) Disc corollas white   162 Brintonia, p. 106
+ Disc corollas yellow   163 Solidago (in part), p. 107
9 (7) Phyllary and corolla nerves orange-resinous; pappi of outer, shorter setae or scales plus inner, longer bristles   186 Erigeron (in part), p. 256
+ Phyllary and corolla nerves not orange-resinous, or only corolla nerves orange-resinous; pappi of equal or unequal bristles.   (10)
10 (9) Phyllaries subequal, foliaceous   169 Toiyabea, p. 172
+ Phyllaries unequal (sometimes subequal, then outer not foliaceous), outer ± herbaceous (sometimes foliaceous), or chartaceous, or proximally indurate   (11)
11 (10) 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)
+ 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 (11) 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   143 Eucephalus (in part), p. 39
+ 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   185 Heterotheca (in part), p. 230
13 (11) Leaf faces densely scabrous and short-stipitate-glandular; phyllaries ± keeled proxi-mally (Esmeralda County, Nevada)   172 Tonestus (in part), p. 181
+ Leaf faces glabrous or canescent, ± puberulent, hispidulous, tomentose, or villous, and/or sometimes ± stipitate-glandular or gland-dotted; phyllaries sometimes keeled   (14)
14 (13) Leaves basal and cauline, basal and proximal petiolate, distal sessile; disc floret style appendages lanceolate   (15)
+ Leaves cauline, sessile; disc floret style appendages triangular   (16)
15 (14) 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   194 Triniteurybia, p. 382
+ 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   197 Dieteria (in part), p. 395
16 (14) Phyllary margins scarious; disc corolla lobes unequal; cypselae obpyramidal, sericeous; pappi of 40–50 tawny bristles   205 Isocoma (in part), p. 439
+ 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 (16) Stems glabrous or scabrous, eglandular; leaf bases not subclasping, margins entire; cypselae prismatic or narrowly turbinate; pappus bristles barbellate   200 Oönopsis (in part), p. 410
+ Stems scabrous to sparsely tomentulose, distally stipitate-glandular; leaf bases subclasping, margins serrate; cypselae fusiform to deltoid; pappus bristles smooth   206 Hazardia (in part), p. 445
18 (1) Rays usually yellow or orange, sometimes cream-colored or white   (19)
+ Rays white, pink, purple, or blue   (38)
19 (18) Pappi 0, or crowns, or of scales   (20)
+ Pappi of bristles, or of outer shorter setae, bristles, or scales plus inner, longer bristles, or of setiform awns.   (21)
20 (19) 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   155 Gutierrezia (in part), p. 88
+ 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   176 Townsendia (in part), p. 193
21 (19) Pappi of outer shorter setae, bristles, or scales plus inner, longer bristles in 2 series   (22)
+ Pappi of setiform scales or bristles in 1–4 series   (26)
22 (21) 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   186 Erigeron (in part), p. 256
+ 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 (22) 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   183 Pityopsis, p. 222
+ 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 (23) Plants proximally woolly, distally arachnose or pilose (hairs flagelliform); basal leaves sessile   182 Chrysopsis (in part), p. 213
+ Plants sparsely to ± densely hispid, strigose, or pilose (hairs not flagelliform); basal leaves petiolate   (25)
25 (24) 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   181 Bradburia (in part), p. 211
+ 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   185 Heterotheca (in part), p. 230
26 (21) 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   202 Grindelia (in part), p. 424
+ 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 (26) Plants ± colonial (rhizomatous); heads usually glomerate, and/or sometimes pedunculate-solitary in flat-topped or multi-storied, corymbiform arrays   158 Euthamia (in part), p. 97
+ 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 (27) Plants rhizomatous (often colonial); heads in dense corymbiform or paniculiform arrays   (29)
+ 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 (28) 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   163 Solidago (in part), p. 107
+ 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   164 Oreochrysum, p. 166
30 (28) 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)
+ 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 (30) 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   163 Solidago (in part), p. 107
+ 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)   206 Hazardia (in part), p. 445
32 (30) 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)
+ 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 (32) 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   195 Xanthisma (in part), p. 383
+ Leaves linear to oblanceolate, coarsely serrate to entire; involucres 7–16 mm; phyllaries herbaceous; disc corolla throats abruptly ampliate, style-branchappendages deltate   204 Rayjacksonia (in part), p. 437
34 (32) Leaves 3-nerved, faces arachnose (in minute, abaxial lacunae); involucresnarrowly turbinate to subcylindric; pappi tawny to reddish brown   184 Croptilon (in part), p. 228
+ 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 (34) Plants sometimes mat-forming; stems clustered; leaves 1–5-nerved; margins of outer phyllaries scarious; pappi whitish   (36)
+ Plants not mat-forming; stems single or clustered; leaves 1-nerved; margins of outer phyllaries herbaceous (sometimes proximally indurate); pappi brownish   (37)
36 (35) 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   170 Stenotus, p. 174
+ 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   172 Tonestus (in part), p. 181
37 (35) 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   200 Oönopsis (in part), p. 410
+ 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   201 Pyrrocoma (in part), p. 413
38 (18) Receptacles conic; rays white (pink or purplish-tinged abaxially)   (39)
+ Receptacles flat or convex; rays white, pink, blue, or purple (not tinged abaxially)   (40)
39 (38) 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   139 Bellis, p. 22
+ 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   188 Aphanostephus (in part), p. 351
40 (38) 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)   190 Chloracantha (in part), p. 358
+ 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 (40) Cypselae usually obconic or obovoid, sometimes lanceoloid, flattened or compressed, margins ribbed (sometimes 1–2 nerves also on faces)   (42)
+ 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 (41) Leaves cauline; phyllaries keeled   (43)
+ Leaves basal and/or cauline; phyllaries not keeled   (44)
43 (42) 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   143 Eucephalus (in part), p. 39
+ 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   150 Ionactis (in part), p. 82
44 (42) Leaf faces eglandular; corolla lobes lanceolate; pappi of 20–30 bristles   138 Aster, p. 20
+ 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 (44) 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   176 Townsendia (in part), p. 193
+ 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   186 Erigeron (in part), p. 256
46 (41) 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)
+ Pappi of bristles or setiform scales   (50)
47 (46) Phyllary midnerves not swollen, not orange-resinous; disc style-branch appendages triangular or lanceolate   (48)
+ Phyllary midnerves (or 1–3 nerves) orange-resinous; disc style-branch appendages deltate   (49)
48 (47) Leaves usually entire, sometimes dentate or lobed, bases clasping or subclasping; phyllaries subequal; pappi rings or crowns of setae or scales   177 Astranthium (in part), p. 203
+ Leaves entire, bases not clasping; phyllaries unequal; pappi thickened rings, crowns of scales (basally fused or distinct), or minute outer scales plus inner bristles   179 Chaetopappa (in part), p. 206
49 (47) 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   186 Erigeron (in part), p. 256
+ 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   189 Boltonia, p. 353
50 (46) Cypselae ± dimorphic (ray 3-sided and rounded abaxially, disc ± compressed); pappi of relatively coarse (± flattened) bristles or setiform scales   (51)
+ Cypselae monomorphic; pappi of relatively fine bristles   (52)
51 (50) Stems simple; leaves mostly basal, margins serrate or serrulate; involucres depressed-hemispheric; cypselae 3–9-ribbed on each face; pappus bristles coarsely barbellate   195 Xanthisma (in part), p. 383
+ 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   198 Arida (in part), p. 401
52 (50) Plants mostly rhizomatous, sometimes with caudices; heads in paniculiform or racemiform arrays, rarely borne singly   (53)
+ 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 (52) Stems spreading-hirsute, eglandular; heads in narrow (wand-shaped), paniculiform arrays; phyllary midribs translucent and swollen; rays 7–9, corollas white to pale cream   163 Solidago (in part), p. 107
+ 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 (53) Phyllaries usually unequal, sometimes subequal, proximally indurate, distally with defined green zone, sometimes distally foliaceous, or outer whollyfoliaceous, sometimes short-stipitate-glandular   214 Symphyotrichum (in part), p. 465
+ Phyllaries subequal, herbaceous (without definite distal green zones, not foliaceous), short-stipitate-glandular   (55)
55 (54) 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   210 Canadanthus, p. 458
+ 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   212 Almutaster, p. 461
56 (52) 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)
+ 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 (56) 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)   208 Corethrogyne (in part), p. 450
+ 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 (57) Stems simple; leaf margins entire; phyllaries mostly foliaceous (margins sometimes proximally indurate); rays white (maturing or drying bluish or purplish)   (59)
+ 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 (58) Leaves basal and cauline (crowded), blades linear-oblanceolate to lanceolate, 1-nerved; phyllaries not keeled; cypselae 5-nerved   179 Chaetopappa (in part), p. 206
+ Leaves mostly basal (rosettes), blades linear to oblanceolate, 3-nerved; phyllaries often ± keeled; cypselae 5–10-nerved (nerves raised)   191 Oreostemma, p. 359
60 (58) 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)   192 Herrickia (in part), p. 361
+ 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 (60) Stems mostly single; cauline leaf blades lanceolate to oblanceolate; phyllaries not keeled   197 Dieteria (in part), p. 395
+ Stems clustered; cauline leaf blades spatulate to obovate oroblong, rarely elliptic; phyllaries keeled   199 Xylorhiza (in part), p. 406
62 (56) Phyllaries flat, not keeled, midveins orange-resinous or swollen and translucent   (63)
+ Phyllaries ± rounded, sometimes ± keeled, midveins not swollen   (64)
63 (62) 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)   144 Doellingeria, p. 43
+ 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   163 Solidago (in part), p. 107
64 (62) 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   149 Oclemena, p. 78
+ 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 (64) Involucres cylindric; ray florets 1–6, white; disc corollas white or cream-colored; cypselae ± densely strigose   160 Sericocarpus, p. 101
+ Involucres cylindro-campanulate or campanulate; rays 5–60, white to purple; disc corollas yellow; cypselae glabrous or ± densely strigillose   (66)
66 (65) 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)   192 Herrickia (in part), p. 361
+ 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   193 Eurybia, p. 365

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