34. Helianthus mollis Lamarck in J. Lamarck et al., Encycl. 3: 85. 1789.
Helianthus mollis var. cordatus S. Watson
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.
Flowering summer–early fall. Prairies, roadsides; 10–600+ m; Ont.; Ala., Ark., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Miss., Mo., Nebr., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Va., W.Va., Wis.
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).