Silverleaf Sunflower

Helianthus argophyllus hybridizes naturally with H. annuus.

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.

Helianthus argophyllus is a North American species of sunflower known by the common name silverleaf sunflower. It is native to the coastal regions of the US state of Texas, and naturalized in other places (Florida, North Carolina, Argentina, Africa, Australia, etc.).

Helianthus argophyllus is an annual herb sometimes as much as 300 cm (10 feet) tall. Leaves and stems appear silvery because of a coating of many hairs along the surface. One plant can produce 1-5 flower heads, each 15–20 ray florets surrounding 150 or more disc florets. The plant grows in sandy areas near the seacoast.

Helianthus argophyllus 'Gold and Silver'