All Floras      Advanced Search
FNA Vol. 20 Page 3,9, 11, 12, 14, 17, 36, 204, 256, 257, 334 Login | eFloras Home | Help
FNA | Family List | FNA Vol. 20 | Asteraceae

186. Erigeron Linnaeus, Sp. Pl. 2: 863. 1753; Gen. Pl. ed. 5, 371. 1754.

Fleabane, érigéron, vergerette [Greek eri, early, or erio, woolly, and geron, old man, perhaps alluding to pappus, which becomes gray and accrescent in some species, or to solitary, woolly heads of some of species]

Guy L. Nesom

Achaetogeron A. Gray; Trimorpha Cassini

Annuals, biennials, or perennials [subshrubs, shrubs, trees], (0.5–)2–90(–100) cm (taprooted, fibrous-rooted, or rhizomatous and fibrous-rooted, sometimes with simple or branched caudices, sometimes stoloniferous). Stems erect to ascending, decumbent, or prostrate, simple or branched, glabrous or hairy, sometimes glandular (hairs 2-seriate, minute, sometimes stipitate). Leaves basal and/or cauline (basal persistent or not to flowering); alternate; sessile or petiolate; blades 1-nerved (3-nerved), linear to lanceolate, oblanceolate, or spatulate (bases sometimes clasping), margins entire or ± dentate to pinnatifid, faces glabrous or hairy, sometimes glandular. Heads usually radiate, sometimes discoid or disciform (erect, nodding, or arching-pendent in bud), borne singly or in loose, corymbiform or paniculiform arrays. Involucres turbinate to hemispheric, 5–35 mm diam. Phyllaries 30–125(–150) in 2–5 series, 1- or 3-nerved (nerves golden-resinous; usually flat, rarely broadly keeled to convex), narrowly elliptic- to linear-lanceolate, unequal to equal, margins scarious or not, faces hairy or glabrous, sometimes glandular. Receptacles flat to conic, pitted, epaleate. Ray florets 0 or 12–350 in 1(–2+) series, pistillate, fertile; corollas usually white to bluish or purplish to pink, less commonly yellow (coiling from apices, reflexing at tube/lamina junction, or remaining ± straight and spreading). Peripheral florets (disciform heads) 50–200 in 1–4 series, pistillate. Disc florets 25–450, bisexual, fertile; corollas yellow (nerves orange-resinous), tubes shorter than usually tubular, sometimes strongly inflated and indurate throats, lobes 5, erect to spreading, deltate; style-branch appendages mostly deltate (papillate). Cypselae (tan) oblong to oblong-obovoid, compressed to flattened, 2(–4)-nerved, or subterete, 5–14-nerved (sect. Wyomingia and some other species), faces glabrous or strigose or sericeous, eglandular; pappi persistent or readily falling, usually of outer setae or scales (0.1–0.4 mm), sometimes connate, plus 5–40(–50), stramineous, barbellate bristles, sometimes pappi only on ray or only on disc cypselae, or 0. x = 9.

Species ca. 390 (173 in the flora): nearly worldwide, mostly in temperate regions.

The North American and Central American species of Erigeron have been divided into sections (G. L. Nesom 1989c, 1990g, 1994b; Nesom and R. D. Noyes 1999), emphasizing variation in habit (especially taprooted versus rhizomatous and fibrous-rooted), vestiture, arrangement of heads in arrays and orientation before flowering (erect, nodding, or arching-pendent), behavior of ray corolla laminae (straight, reflexing, or coiling), cypsela and pappus morphology, and other morphologic features. The sequence and groupings of species treated here reflect significant modifications of earlier arrangements.

G. L. Nesom (1989d) hypothesized that Trimorpha [Erigeron sect. Trimorpha (Cassini) de Candolle] is separate from Erigeron, more closely related to Conyza. Studies by W. Huber and colleagues (e.g., Huber 1993; Huber and Ö. Nilsson 1995) and R. D. Noyes (2000) have shown that Trimorpha species are closely related to those of sect. Erigeron and that both sections are relatively recently derived within the genus. As suggested by Nesom (1994b) and by Huber and Nilsson, and as discussed in detail and experimentally confirmed by Noyes, autogamous breeding systems apparently have arisen independently in groups of Astereae, including Trimorpha and Conyza, where the pistillate florets of a head are greatly increased in number (often outnumbering the bisexual florets), in multiple series, the inner sometimes with filiform, elaminate corollas, and the outer with reduced laminae.

In the molecular analysis by R. D. Noyes (2000), Conyzinae comprises Erigeron, American Conyza, the four genera of the South American Leptostelma group, and the North American Aphanostephus; the cladistically basal and terminal taxa of the subtribe are members of Erigeron. Noyes (p. 107) observed that "strictly speaking, although the Conyzinae form a monophyletic group [with caveats regarding Old World Conyza], Erigeron is paraphyletic, as five other genera are derived from within it." The molecular study included 46 of the 173 species treated here.

Polyploidy is common among species of Erigeron, and agamospermy apparently is a common correlate of polyploidy, especially in odd-polyploid plants. Molecular phylogenetic data (R. D. Noyes 2000) indicate that agamospermy has arisen at least three times within the genus.

In the descriptions and keys, some characteristics are assumed constant unless otherwise indicated (usually in parentheses); particular application of terms is discussed here. The indumentum of erigerons is often complex; in order to simplify descriptions, glabrous applies here only to absence of non-glandular hairs, eglandular to the absence of glandular hairs; a totally glabrous plant (in the usual sense) would be glabrous and eglandular. Petiole margins are eciliate or sparsely ciliate unless otherwise indicated. Leaf bases of most erigerons are broadened or not, not thickened and white-indurate. Margins of leaves in some erigerons are entire but for tiny callous enations that correspond to the callous tips of teeth on some leaves with serrate margins. Here, margins with such tiny enations are described as denticulate. Heads of some erigerons are "pseudodisciform" in the sense that the outer pistillate florets have relatively small, ± filiform laminae (such florets are technically "ray florets" even though their "rays" are inconspicuous) and the inner pistillate florets have no laminae on their corollas. The distinction between corollas without and those with laminae is sometimes arbitrary. Ray laminae are considered strap-shaped and spreading unless otherwise indicated. Descriptions of ray color as "blue" should be read as lavender-blue.

Artificial distinctions are used in the key to groups of species recognized by leafy runners, pinnately lobed or dissected leaves, discoid or disciform heads, and yellow rays. Otherwise, species tend to be identified within natural groups. Couplets that use basal parts for distinction or inference of duration may be difficult if collections lack diagnostic basal parts or if the nature of the basal parts is not clear. Yet, these differences are significant in delimiting species groups and often critical in identification, and the pertinent species otherwise would be scattered widely in a more artificial key.


Cronquist, A. 1947. A revision of the North American species of Erigeron, north of Mexico. Brittonia 6: 121–302. Nesom, G. L. 1989c. Infrageneric taxonomy of New World Erigeron (Compositae: Astereae). Phytologia 67: 67–93. Nesom, G. L. 1989d. The separation of Trimorpha (Compositae: Astereae) from Erigeron. Phytologia 67: 61–66. Nesom, G. L. 1990g. Taxonomy of the Erigeron coronarius group of Erigeron sect. Geniculactis (Asteraceae: Astereae). Phytologia 69: 237–253. Nesom, G. L. 2004e. Taxonomic reevaluations in North American Erigeron (Asteraceae: Astereae). Sida 21: 19–40. Nesom, G. L. and R. D. Noyes. 1999. Notes on sectional delimitations in Erigeron (Asteraceae: Astereae). Sida 18: 1161–1165.

Group 14

1 Stems densely white-strigose (at least proximally), eglandular; leaves linear   53 Erigeron filifolius (in part)
+ Stems glabrous or villous, puberulous, hispid, or hirsute, or, if sparsely strigose, then not whitish because of vestiture, glandular or eglandular; leaves mostly narrowly obovate to oblanceolate, oblong, or elliptic, if linear, then stems glabrous or sparsely strigose   (2)
2 (1) Stems sparsely villous, minutely stipitate-glandular   104 Erigeron aequifolius
+ Stems puberulous, villous, hispid, hirsute, hirsutulous, sparsely strigose, or glabrous, eglandular   (3)
3 (2) Stems puberulous to villous, hispid, or hirsute to hirsutulous (hairs spreading to spreading-deflexed)   (4)
+ Stems glabrous or sparsely strigose (hairs ascending-appressed)   (8)
4 (3) Phyllaries densely canescent-hirsutulous, minutely glandular; stems puberulous to villosulous (hairs crisped); cypselae glabrous   94 Erigeron blochmaniae
+ Phyllaries either densely minutely glandular (otherwise glabrous or sparsely hairy) or hispido-hirsute and minutely glandular; stems densely hirsutulous to hirsute, hispidulous, hispido-hirsute, or piloso-hirsute (hairs straight, spreading to deflexed); cypselae strigose   (5)
5 (4) Phyllaries strigoso- to hispido-hirsute, minutely glandular   106 Erigeron breweri (in part)
+ Phyllaries glabrous or sparsely hairy, densely glandular   (6)
6 (5) Plants 7–15 cm; stems prostrate to procumbent or decumbent   106 Erigeron breweri (in part)
+ Plants 6–15(–20) or 20–60 cm; stems usually ascending   (7)
7 (6) Plants 6–15(–20) cm; caudex branches with lignescent offsets from woody roots; stem hairs spreading, 0.2–1 mm; inner phyllaries lacking green apical areas (margins white, relatively broad, thickened)   95 Erigeron klamathensis
+ Plants 12–60 cm; caudex branches rhizomelike, fibrous-rooted; stem hairs slightly to strongly deflexed, 0.1–0.4 mm; inner phyllaries with green apical areas   106 Erigeron breweri (in part)
8 (3) Stems with axillary tufts of smaller leaves at most nodes; margins of inner phyllariesbroadly scarious   105 Erigeron mariposanus
+ Stems without axillary leaf tufts; margins of inner phyllaries narrowly scarious   (9)
9 (8) Stems prostrate to decumbent-trailing; rhizomes relatively slender, fibrous-rooted,or caudex branches rhizomelike; leaves 5–20 mm   107 Erigeron elmeri (in part)
+ Stems erect or ascending; taproots woody; leaves 10–50(–100) mm   (10)
10 (9) Mid and distal cauline leaves shorter than internodes, eciliate   93 Erigeron oxyphyllus
+ Mid and distal cauline leaves longer than internodes, ciliate (cilia ascending-apressed)   (11)
11 (10) Cilia on leaf margins thick-based; phyllaries glabrous or moderately to densely strigoso-hirsute, sometimes densely and prominently glandular; rays 15–60   96 Erigeron foliosus
+ Cilia on leaf margins thin-based; phyllaries glabrate (barely perceptible), densely minutely glandular; rays 9–13   98 Erigeron serpentinus

List of Keys

  • List of lower taxa


    Related Objects  

    Flora of Chile  
  • PDF
  • PDF

  •  |  eFlora Home |  People Search  |  Help  |  ActKey  |  Hu Cards  |  Glossary  |