Vernonia

Perennials, 2–20(–30+) dm (rhizomatous or not). Leaves usually mostly cauline (rarely mostly basal or basal and cauline); sessile or petiolate; blades ovate, elliptic, lanceolate, oblanceolate, spatulate, linear, or filiform, bases usually ± cuneate (rounded-truncate in V. pulchella), margins usually toothed (rarely entire), apices acute to attenuate, abaxial faces usually ± scabrellous to strigillose or tomentose to pannose, sometimes glabrate or glabrous, usually resin-gland-dotted (sometimes ± pitted), adaxial faces ± scabrellous or glabrate, sometimes resin-gland-dotted (rarely pitted). Heads discoid, ± pedunculate, not subtended by foliaceous bracts, (6–)40–100+ in ± corymbiform to paniculiform arrays (6–)10–25+ cm diam. Involucres ± campanulate to obconic or hemispheric, 3–8(–11+) mm diam. Phyllaries 18–70+ in 4–7+ series, the outer ovate to lanceolate or subulate, inner ± lanceolate to oblong, all ± chartaceous, margins entire, often ciliolate, tips rounded (then sometimes apiculate), or acuminate, subulate, or filiform, faces glabrous or sparsely strigillose to tomentose, sometimes ± gland-dotted. Florets 9–30(–65+); corollas usually purplish or pink (rarely white), tubes longer than funnelform throats, lobes 5, lance-linear, ± equal. Cypselae ± columnar, sometimes arcuate, 8–10-ribbed, glabrous or ± strigillose to hirtellous, often resin-gland-dotted; pappi persistent, of 20–30+ outer, erose to subulate scales or bristles plus 20–40+ inner, longer, subulate to setiform scales or bristles. x = 17.

Distribution

Mainly c, e North America, n Mexico, 2–3 species in South America.

Discussion

Species 20 or so (17 in the flora).

The circumscription of Vernonia adopted here follows that of H. Robinson (1999).

Vernonias hybridize; almost every one of the species recognized here has been noted as sometimes hybridizing with one or more others. Putative hybrid plants are usually intermediate between parentals in some traits; such plants may not “key” satisfactorily to any of the species treated here. Some putative hybrids have been named. Vernonia guadalupensis is “without much doubt a hybrid of V. baldwinii Torrey and V. lindheimeri Engelmann & Gray” (L. H. Shinners 1950); V. vulturina Shinners (known only from the type collection) may be a product of V. baldwinii × V. marginata; V. ×georgiana Bartlett may refer to V. acaulis × V. angustifolia. Additional putative hybrids (S. B. Jones 1964) are V. ×concinna Gleason (V. ovalifolia × V. angustifolia), V. ×dissimilis Gleason (V. altissima × V. angustifolia), and V. ×recurva Gleason (V. pulchella × V. angustifolia).

In the key and descriptions, “l/w = ” refers to lengths divided by widths for blades of leaves; lengths of phyllaries include subulate to filiform tips (if any).

Selected References

Gleason, H. A. 1922b. Vernonia. In: N. L. Britton et al., eds. 1905+. North American Flora…. 47+ vols. New York. Vol. 33, pp. 52–95.

Jones, S. B. 1964. Taxonomy of the narrow-leaved Vernonia of the southeastern United States. Rhodora 66: 382–401.

Jones, S. B. and W. Z. Faust. 1978. Vernonia. In: N. L. Britton et al., eds. 1905+. North American Flora…. 47+ volumes. New York. Ser. 2, part 10, pp. 180–195.

Shinners, L. H. 1950. Notes on Texas Compositae. IV. Field & Lab. 18: 25–32.

Lower Taxa

Vernonia acaulis, Vernonia angustifolia, Vernonia arkansana, Vernonia baldwinii, Vernonia blodgettii, Vernonia fasciculata, Vernonia flaccidifolia, Vernonia gigantea, Vernonia glauca, Vernonia larseniae, Vernonia lettermannii, Vernonia lindheimeri, Vernonia marginata, Vernonia missurica, Vernonia noveboracensis, Vernonia pulchella, Vernonia texana

Key

1	Phyllary tips usually subulate to filiform, sometimes acuminate	> 2
1	Phyllary tips usually acute to rounded or rounded-apiculate, seldom acuminate	> 7
2	Leaves mostly basal (cauline leaves much smaller with narrower blades)	Vernonia acaulis
2	Leaves mostly cauline (basal leaves wanting at flowering or ± like cauline)	> 3
3	Involucres 11–15 mm diam.; phyllaries (50–)60–70+; florets 50–100+	Vernonia arkansana
3	Involucres 4–8(–10) mm diam.; phyllaries 22–46(–60+); florets 12–45(–65)	> 4
4	Involucres ± campanulate to obconic; florets 12–24(–30+)	> 5
4	Involucres ± hemispheric; florets 30–45(–65)	> 6
5	Leaf blades (mid stem) lance-linear to filiform, 5–12 cm × 2–4(–8+) mm.	Vernonia angustifolia
5	Leaf blades (mid stem) oblanceolate to lance-linear, 3–7 cm × (5–)10–20+ mm	Vernonia pulchella
6	Leaf blade l/w = 2.5–3.5(–4); pappi stramineous to whitish, outer bristles or subulate scales intergrading with inner ones	Vernonia glauca
6	Leaf blade l/w = (3.3–)4–6+; pappi fuscous to purplish, outer scales contrasting with inner bristles	Vernonia noveboracensis
7	Phyllaries densely sericeo-tomentose to pannose	> 8
7	Phyllaries usually glabrous or puberulent to scabrellous (rarely sparsely arachno-tomentose)	> 9
8	Leaf blades adaxially densely sericeo-tomentose; florets 40–50+	Vernonia larseniae
8	Leaf blades adaxially usually glabrate, sometimes sparsely arachno-tomentose; florets 12–24+	Vernonia lindheimeri
9	Leaf blades abaxially glabrate (and pitted; best seen at 10× or greater, pits containing awl-shaped hairs or glands 0.1–0.5+ mm)	> 10
9	Leaf blades abaxially scabrellous, scaberulous, or puberulous to tomentose or pannose (not pitted)	> 13
10	Involucres obconic to hemispheric; cypselae 2–3 mm	Vernonia texana
10	Involucres campanulate; cypselae 3–5 mm	> 11
11	Leaf blades 1–3+ mm wide; florets 10–12+	Vernonia lettermannii
11	Leaf blades (2.5–)5–20(–40) mm wide; florets (10–)15–25+	> 12
12	Peduncles (3–)10–35 mm; involucres (7–)9–11 mm; phyllary tips ± acuminate; inner pappi 8–9+ mm	Vernonia marginata
12	Peduncles 1–8(–12+) mm; involucres 5–7(–8+) mm; phyllary tips acute or rounded-apiculate; inner pappi 5–7+ mm	Vernonia fasciculata
13	Leaf blades 2–8+ mm wide	Vernonia blodgettii
13	Leaf blades 15–40(–75+) mm wide	> 14
14	Stems glabrous	Vernonia flaccidifolia
14	Stems puberulent to tomentose (sometimes glabrescent)	> 15
15	Leaf blades abaxially usually scabrellous (with appressed, awl-shaped hairs), sometimes glabrescent, not or sparsely resin-gland-dotted	Vernonia gigantea
15	Leaf blades abaxially usually puberulous to tomentose or pannose (with ± erect, ± curled hairs), seldom glabrescent, conspicuously resin-gland-dotted	> 16
16	Involucres broadly campanulate to urceolate, (6–)7–10+ × 5–9+ mm; (phyllaries seldom resin-gland-dotted); florets 30–55	Vernonia missurica
16	Involucres broadly campanulate to hemispheric, 4–6(–8+) × 4–7+ mm; (phyllaries often resin-gland-dotted); florets (15–)20–25(–35+)	Vernonia baldwinii