39. Helianthus floridanus A. Gray ex Chapman, Fl. South. U.S. ed. 2. 629. 1883.
Perennials, 100–200 cm (rhizomatous). Stems (green) erect, hispid to hispidulous. Leaves cauline; usually opposite or alternate, rarely whorled; petioles 0–1 cm; blades (1- or 3-nerved) lanceolate to elliptic or lance-ovate, 4–15 × 0.5–6 cm, bases rounded to cuneate, margins entire or serrulate (often undulate, often ± revolute), faces ± scabrous to tomentulose and gland-dotted (abaxial) or scabrous (adaxial). Heads 1–6. Peduncles 2–15 cm. Involucres ± hemispheric, 12–19 × 7–9 mm. Phyllaries 33–38, lanceolate, 5–9 × 1.5–3 mm, apices (at least outer) obtuse, abaxial faces hispidulous to hispid, gland-dotted. Paleae 4.5–6 mm, entire or weakly 3-toothed (apices purplish, glabrate to puberulent, often gland-dotted). Ray florets 10–20; laminae 20–25 mm (abaxial faces gland-dotted). Disc florets 90+; corollas 4–5 mm, lobes usually reddish, sometimes yellow; anthers dark brown or black, appendages dark (style branches yellow). Cypselae 2.5–3 mm, glabrous; pappi of 2 aristate scales 1.5–2.2 mm. 2n = 34.
Flowering late summer to fall. Sandy, open areas; 0–50 m; Ala., Fla., Ga., La., N.C., S.C.
Helianthus floridanus is similar to and intergrades with H. angustifolius, which has narrower leaves, and H. simulans, which is more robust and has longer leaves without undulate margins.