Helianthus mollis Lam.

Helianthus mollis is introduced in Ontario and adventive in the eastern United States (e.g., Maine), where it is continuing to spread, particularly along roads. Natural hybrids between H. mollis and H. occidentalis have been named H. cinereus Torrey & A. Gray (R. C. Jackson and A. T. Guard 1957); they differ from H. mollis by having smaller heads with fewer ray florets and narrower leaves with cuneate bases. Hybrids of H. mollis with H. giganteus have been called H. doronicoides Lamarck (Jackson 1956).

Perennials, 50–150+ cm (rhizoma-tous). Stems erect, hirsute to villous. Leaves mostly cauline; mostly opposite (sometimes alternate among heads); sessile; blades (ashy or gray-green, 3-nerved distal to bases) lance-olate to broadly ovate, 5.5–14.5 × 1.8–6.5 cm, bases rounded to cordate, margins entire or serrulate, abaxial faces hispid to tomentose, gland-dotted. Heads 1–15. Peduncles 0.1–15 cm. Involucres broadly hemispheric, 12–25 mm diam. Phyllaries 30–40, lanceolate, (5–)10–16 × 2–3.5 mm, apices usually acute, sometimes acuminate, abaxial faces densely hispid to villous or tomentose, densely gland-dotted. Paleae (oblanceolate) 9–11 mm, entire (1-toothed, densely hairy, densely gland-dotted). Ray florets 17–22; laminae 25–30 mm (abaxial faces densely gland-dotted). Disc florets 75+; corollas 6–7.5 mm, lobes yellow; anthers dark, appendages dark. Cypselae 3.5–4 mm, distally villous; pappi of 2 aristate scales 2.8–3.2 mm. 2n = 34.

Helianthus mollis var. cordatus S. Watson

Helianthus mollis is a species of sunflower known by the common names ashy sunflower, hairy sunflower or downy sunflower. It is widespread across much of the United States and Canada, primarily the Great Lakes region from Ontario south to Texas and Alabama. Additional populations are found in the states of the Atlantic Coast from Maine to Georgia, but these appear to be introduced.

Helianthus mollis grows on prairies, roadsides, dry open woods, rocky glades, fields, and thickets. It is a perennial herbaceous plant up to 1.5 m (4.9 ft) tall, spreading by means of underground rhizomes. The leaves are mostly along the stem rather than crowded near the base, each egg-shaped with teeth along the edges. One plant produces 1-15 flower heads containing 17-22 yellow ray florets surrounding 75 or more yellow disc florets. Flowers bloom from July to September. The Latin specific epithet mollis means soft and is in reference to the downy plant hairs.