Prairie Ironweed

Plants 3–12+ dm. Stems puberulent, glabrescent. Leaves mostly cauline; blades ± lanceolate, 5–12(–20+) cm × 5–18(–40+) mm, l/w = 5–9(–14+), abaxially glabrate (pitted, with awl-shaped hairs in pits), adaxially scabrellous, resin-gland-dotted (sometimes pitted). Heads in congested, corymbiform arrays. Peduncles 1–8(–12+) mm. Involucres ± campanulate, 5–7(–8+) × 4–6 mm. Phyllaries 25–35+ in 4–5+ series, glabrescent, margins arachno-ciliolate, the outer lance-ovate, 1–3 mm, inner oblong to linear-oblong, 5–7+ mm, tips acute or rounded-apiculate. Florets 12–25+. Cypselae 3.5–4 mm; pappi fuscous to purplish, outer subulate scales or bristles 20–30, 0.5–3+ mm, intergrading with 35–45+, 5–7+ mm inner subulate scales or bristles. 2n = 34.

Vernonia fasciculata subsp. corymbosa (Schweinitz) S. B. Jones; V. fasciculata var. corymbosa (Schweinitz) B. G. Schubert

Vernonia fasciculata Michx. Fl. Bor. Am. 2: 94. 1803
Cacalia fasciculata Kuntze, Rev. Gen. 970. 1891.
Vernonia fasciculata nebraskensis Gleason, Bull. Torrey Club 46: 247. 1919.
Stems erect, glabrous, purple or greenish-purple, 6-12 dm. high; leaves numerous, erect or ascending, the blades thin, bright-green, linear to narrowly lanceolate, or broadly lanceolate in some forms, 8-15 cm. long, 4-7 mm. wide, long-acuminate or acute, denticulate to sharply dentate with ascending or salient teeth, narrowed to a sessile base, glabrous on both sides or minutely puberulent, deeply pitted beneath; inflorescence dense, hemispheric or flattened, 4-10 cm. wide; heads crowded, sessile or short-peduncled, 18-21 -flowered; involucre narrowly campanulate to subcylindric, 6 mm. high, red or purple; scales appressed and regularly imbricate, subacute to rounded, glabrous, sparsely ciliate, or rarely puberulent, the exposed portion not more than 2 mm. wide; achenes 3 mm. long, puberulent on the ribs, resinous in the furrows; pappus purple, the inner bristles 7-8 mm. long, the outer series similar but shorter.
Type locality: Illinois.
Distribution: Ohio to Minnesota and Oklahoma.

Vernonia fasciculata, the smooth ironweed or common ironweed, or prairie ironweed is a species of perennial plant in the family Asteraceae. It is native to Manitoba in Canada and the north-central U.S.A.

Vernonia fasciculata inhabits areas with moist soils and prairies. It flowers in July to September.