Helianthus decapetalus L.

Perennials, 60–200 cm (rhizomatous). Stems erect, glabrous. Leaves cauline; opposite (proximal or all) or alternate (distal); petioles (1–)2–5 cm; blades (green, 3-nerved distal to bases) lanceolate to ovate, 7–21 × 4–10 cm, bases rounded to cuneate (often shortly decurrent onto petioles, margins usually serrate (moderately to notably in larger leaves), abaxial faces ± scabro-hispidulous, relatively sparsely gland-dotted. Heads 3–6(–10). Peduncles 2–12 cm (not gland-dotted). Invo-lucres hemispheric, 12–25 mm diam. Phyllaries 20–25 (often reflexed), lance-linear to lanceolate, 11–16 × 2–3 mm (sometimes leaflike, longest surpassing discs by 1/2+ their lengths), (margins ciliate) apices attenuate, abaxial faces strigillose to glabrate, not gland-dotted. Paleae 8–10 mm, 3-toothed. Ray florets 8–12; laminae 20–25 mm. Disc florets 40+; corollas 6.5–7.2 mm, lobes yellow; anthers usually dark brown to black (rarely reddish brown ), appendages dark or reddish brown. Cypselae 3.5–5 mm; pappi of 2 aristate scales 3–4 mm. 2n = 34, 68.