Arkansas Ironweed

Vernonia arkansana was published in April, V. crinita in October 1838.

Plants 8–12(–20) dm. Stems scab-rellous to pilosulous, glabrescent. Leaves mostly cauline; blades lance-linear, 6–14(–20) cm × 7–15(–25) mm, l/w = 7–10(–18), abaxially scabrellous (hairs awl-shaped), resin-gland-dotted, adaxially scaberulous, glabrescent, resin-gland-dotted. Heads in ± corymbiform arrays. Peduncles 2–5 cm. Involucres ± hemispheric, 11–15 × 11–15 mm. Phyllaries (50–)60–70+ in 5–6 series, scabrellous (and resin-gland-dotted), margins ciliolate, the outer lance-ovate, 3–8+ mm, inner lanceolate, 12–15 mm, tips subulate to filiform. Florets 50–100+. Cypselae 3–5 mm; pappi fuscous to purplish, outer scales 25–30+, 0.5–1 mm, contrasting with 25–30+, 5–7 mm inner bristles. 2n = 34.

Vernonia crinita Rafinesque

Vernonia crihita Raf. New Fl. 4: 77. 1838
Vernonia arkansana DC. Prodr. 7: 264. [?D] 1838. Cacalia arkansana Kuntze, Rev. Gen. 969. 1891.
Stems erect, simple or sparingly branched, leafy, glabrous and somewhat glaucous to
minutely puberulent, 1-3 m. high; leaf-blades narrowly lanceolate to broadly linear, 8-15 cm.
long, 5-20 mm. wide, acuminate, entire or with scattered callous teeth, tapering to the base,
glabrous or sparingly pubescent; inflorescence with 5-40 heads; peduncles stout, thickened
above; heads 55-S9-flowered; involucre broadly hemispheric, 12-20 mm. wide; scales glabrous
or pubescent, especially at the tip, lanceolate or ovate at the appressed base, acuminate into
long, flexuous, subulate, erect or spreading tips, involute below, becoming filiform above;
achenes strongly ribbed, glabrous or nearly so, usually resinous in the furrows, 5-6 mm.
long; pappus dull-purple, the bristles 6-7 mm. long.
Type locality: Arkansas.
Distribution: Missouri, Kansas, Arkansas, and Oklahoma.

Vernonia arkansana (also known as Arkansas ironweed and great ironweed) is a species of perennial plant from family Asteraceae found in south-central United States. The plant is 4–6 feet (1.2–1.8 m) high and 3–4 feet (0.91–1.22 m) wide. The flowers bloom from August to September and are pink-purple coloured. The cultivar 'Mammuth' is a recipient of the Royal Horticultural Society's Award of Garden Merit.