New Fl. 4: 81. 1838.
Perennials, 30–100 cm. Stems usually 1, usually branched distally, strongly winged, glabrous or sparsely hairy proximally, sparsely to moderately hairy distally. Leaves glabrous or sparsely to moderately hairy; basal blades oblanceolate to obovate or spatulate, entire or serrate; proximal and mid-blades oblanceolate to lanceolate, entire or toothed; distal blades lanceolate to lance-linear, entire. Heads (1–) 5–50 (–80+) per plant, in paniculiform arrays. Peduncles 3–10 cm, sparsely to moderately hairy. Involucres globoid to usually ovoid, 8–17 × 9–17 mm. Phyllaries (connate proximally) moderately to densely hairy. Ray-florets usually 8–13, neuter, sometimes 0; corollas yellow to reddish-brown to red to purple, 10–20 × 5–10 mm. Disc-florets 250–500 (–700+); corollas yellow proximally and purple distally or purple throughout, 2.3–3.7 mm, lobes 4 (–5). Cypselae 1–1.2 mm, moderately hairy; pappi of 5–6 entire, aristate scales 0.6–1 (–1.7) mm. 2n = 28.
Phenology: Flowering (Apr–)May–Jul(–Oct).
Habitat: Ditches, fields, washes, along streams
Elevation: 10–900 m
N.S., Ont., Que., Ala., Ark., Fla., Ga., Ill., Ind., Ky., La., Md., Mass., Mich., Miss., Mo., N.J., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va., Wis.
It has been suggested that Helenium flexuosum may be of hybrid origin from H. campestre (perennial, 2n = 28) and some member of Helenium sect. Tetrodus (H. F. L. Rock 1957). The only member of sect. Tetrodus that has a chromosome number of 2n = 28 is H. linifolium, an annual from southern Texas.