Silverleaf sunflower

Annuals, 100–300 cm. Stems (silvery white) erect, usually tomentose or floccose. Leaves mostly cauline; mostly alternate; petioles 2–10 cm; blades ovate to lance-ovate, 15–25 × 10–20 cm, bases truncate to subcordate, margins entire or serrulate, abaxial faces usually floccose, sericeous, or tomentose, gland-dotted . Heads 1–5. Peduncles 2–8 cm. Involucres hemispheric, 20–30 mm diam. Phyllaries 20–35, ovate to lance-ovate, 15–18 × (2–)5–8 mm, apices long-attenuate, abaxial faces usually densely white-villous, gland-dotted. Paleae 10–11 mm, 3-toothed (apices glabrous or sparsely villous). Ray florets 15–20; laminae 20–30 mm. Disc florets 150+; corollas 6.5–7.5 mm, lobes reddish; anthers dark, appendages dark (style branches reddish ). Cypselae 4–6 mm, glabrate; pappi of 2 aristate scales 2–2.7 mm. 2n = 34.

Flowering late summer–fall. Open areas, sandy soils; 0–30+ m; Fla., N.C., Tex.; introduced in South America (Argentina), Africa, Australia.

Helianthus argophyllus hybridizes naturally with H. annuus.