Longdisk sneezeweed

Annuals, 30–100 cm. Stems usually 1, branched distally, moderately to strongly winged, glabrous or sparsely hairy. Leaves glabrous or sparsely hairy; blades narrowly elliptic to lance-linear, usually entire; proximal blades sometimes pinnately lobed. Heads 5–15(–50+) per plant, in paniculiform arrays. Peduncles 3–13 cm, sparsely to moderately hairy. Involucres ovoid to conic, 7–11(–14) × 6–11 mm. Phyllaries (connate proximally) sparsely to densely hairy. Ray florets 10–15, pistillate, fertile; corollas yellow, 7–12.4 × 4–8.8 mm. Disc florets 225–500+; corollas yellow proximally, yellow to brown to reddish brown distally, 1.1–1.8 mm, lobes 4. Cypselae 0.6–1.2 mm, moderately hairy; pappi of usually 6 entire, non-aristate scales 0.1–0.3 mm. 2n = 26.

Flowering Mar–Jun (year round). Sandy or clay soils, ditches, around ponds and lakes, along streams; 0–1800 m; Ala., La., Miss., Pa., Tex.; Mexico; West Indies (Cuba); Central America (Belize, Guatemala).

Helenium quadridentatum is introduced in Pennsylvania.