5. Helenium flexuosum Rafinesque, New Fl. 4: 81. 1838.
Purplehead sneezeweed, hélénie nudiflore
Helenium nudiflorum Nuttall
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.
Flowering (Apr–)May–Jul(–Oct). Ditches, fields, washes, along streams; 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.