Vernonia angustifolia
Asteraceae tribe Vernonieae
tall ironweed
sparsely appressed-puberulent, glabrescent.
mostly cauline;
blades (mid stem) lance-linear to filiform, 5–12 cm × 2–4(–8+) mm, l/w = (8–)12–30(–60+), abaxially glabrous but for scattered hairs on midribs or scabrellous (hairs awl-shaped), resin-gland-dotted or not, adaxially scabrellous.
usually cauline, sometimes basal or basal and cauline; alternate (rarely subopposite distally) [opposite]; usually petiolate, sometimes sessile (or petioles winged);
margins usually ± dentate, sometimes entire [lobed or dissected].
8–25 mm.
± campanulate to obconic, 5–7(–10) × 4–6(–9) mm.
flat to convex, usually epaleate (often foveolate, sometimes setose).
12–20(–30).
0 (corollas of peripheral florets enlarged, zygomorphic, ± raylike in Stokesia).
bisexual, fertile;
corollas white, ochroleucous, or pink to cyanic [yellow];
anther bases ± sagittate [tailed], apical appendages ovate to lanceolate;
styles abaxially hirsutulous (at least distally), branches lance-linear to ± lanceolate, adaxially continuously stigmatic from bases nearly to apices, apices acute, appendages essentially none.
22–45+ in 5–6 series, sparsely scabrellous, glabrescent, margins ciliolate, the outer lanceolate to subulate, 1.5–3 mm, inner lance-ovate to lanceolate, 5–9+ mm, tips acuminate to subulate.
usually persistent [readily falling], in 2–8+ series, distinct, unequal, herbaceous to chartaceous, margins and/or apices sometimes scarious.
0.
in ± corymbiform to paniculiform arrays.
homogamous (discoid, pseudo-radiant or -liguliflorous in Stokesia), usually in corymbiform, paniculiform, or scorpioid arrays, sometimes borne singly or in glomerules [aggregated in second-order heads].
2.5–3 mm;
pappi stramineous to purplish, outer scales 25–30, 0.5–1.2+ mm, contrasting with 35–40+, 5.5–6+ mm inner bristles.
± monomorphic within heads, columnar to clavate, fusiform, or prismatic, sometimes compressed, not beaked, bodies smooth, nerved, or ribbed (glabrous or hirsutulous to strigillose, sometimes resin-gland-dotted as well);
pappi usually persistent, usually in 2 series (outer series of shorter, stouter bristles or narrow scales, inner of longer, usually barbellate bristles), sometimes in 1 series (bristles or scales, scales often aristate).
= 34.
Vernonia angustifolia
Asteraceae tribe Vernonieae
Genera 100–140, species ca. 1300 (6 genera, 25 species in the flora).
Most members of Vernonieae are herbs, subshrubs, or shrubs (Vernonia arborea Buchanan-Hamilton of tropical Asia may form trees to 33 m). They are characterized by discoid heads of bisexual florets with purple to pink or white corollas, calcarate anthers, attenuate, abaxially hirsutulous style branches stigmatic ± uniformly (rather than in two lines or bands) nearly to their tips, and pollen grains with regular, polygonal, patterns of ± spiny to smooth ridges. Centers of species concentration for the tribe are found in Africa, Madagascar, South America, and Antilles. In the flora, most species are found in the eastern and southern states of the United States. The plants are often associated with open, prairie or savanna-like areas.
Treating clades recognized by J. L. Panero and V. A. Funk (2002) as corresponding to tribes, Vernonieae is sister to Liabeae (none in the flora) and is included with Arctotideae (introduced), Cichorieae, and Gundelieae (none in the flora) within Cichorioideae.
Historically, 80% or so of the species in the tribe were included in Vernonia. H. Robinson (1999) has argued for resurrections and recircumscriptions of some old genera and recognition of some “new” genera, resulting in a Vernonia of ca. 20 species.
Stokesia laevis and some Vernonia species are grown as ornamentals. Some Vernonia species have been used medicinally in folk remedies and some may be locally troublesome as weeds (e.g., V. baldwinii).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Heads pseudo-radiant (corollas of peripheral, bisexual florets enlarged, zygomorphic); margins of phyllaries (at least the outer), pectinately spinose-toothed | Stokesia |
1. Heads ± discoid; margins of phyllaries not pectinately spinose-toothed | → 2 |
2. Heads sessile, borne in congested clusters; florets (1–)4(–5) in each head | → 3 |
2. Heads mostly pedunculate, not borne in congested clusters; florets 9–100+ in each head | → 4 |
3. Heads (1–)10–40 per cluster, each cluster subtended by (2–)3 ± deltate bracts; pappi of 5(–6) 1-aristate scales (look closely for squamiform, gradually to abruptly tapering base of each arista), no scales tipped with plicate aristae | Elephantopus |
3. Heads 1–5+ per cluster, each cluster subtended by 1–2 lanceolate to spatulate or linear bracts; pappi of 6–10 ± laciniate to aristate scales, 2(–3+) of aristate scales each with awnlike arista plicate (2-folded) distally | Pseudelephantopus |
4. Annuals (perhaps persisting); cypselae not ribbed | Cyanthillium |
4. Perennials or functionally annuals; cypselae 8–10-ribbed | → 5 |
5. Heads each subtended by 3–8+, ± foliaceous bracts; pappi caducous | Centratherum |
5. Heads not each subtended by foliaceous bracts; pappi persistent | Vernonia |
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