2. Heliopsis helianthoides (Linnaeus) Sweet, Hort. Brit. 487. 1826.
False sunflower, oxeye, smooth oxeye, héliopside faux-hélianthe
Buphthalmum helianthoides Linnaeus, Sp. Pl. 2: 904. 1753
Perennials, (40–)80–150 cm. Aerial stems (from creeping rhizomes to 4 cm × 2–6 mm, rhizome internodes mostly 2–10 mm) 1–10+, stramineous to reddish brown, glabrous or hairy. Leaf blades ovate to deltate-lanceolate, 6–12(–15) × 2–6(–12) cm, margins regularly to irregularly and coarsely dentate, apices acute to acuminate, faces glabrous, sparsely pubescent, moderately to densely scabrellous, or scabrous. Heads 1–15+. Peduncles 9–25 cm. Involucres 12–25 mm diam. Phyllaries glabrescent to densely pubescent on margins, apices, and abaxial faces. Paleae lanceolate to oblong, apices obtuse, faces glabrous. Ray florets 10–18; corollas golden yellow, laminae mostly 2–4 cm × 6–13 mm. Disc florets 10–75+; corollas yellowish to brownish yellow (lobes brighter than tubes), 4–5 mm, glabrous. Cypselae 4–5 mm, glabrous or pubescent on angles, smooth; pappi 0 or of 2–4 minute, toothlike scales. 2n = 28 (variety unknown).
Varieties 2 (2 in the flora): e North America.
As T. R. Fisher (1957) noted, intermediates occur between var. helianthoides and var. scabra, and artificial hybrids show only slightly decreased pollen stainabilities and normal meiotic pairing. Intermediates are especially common in Missouri, Illinois, and New England, and may also be encountered elsewhere in areas of sympatry. In addition to the key characters, var. helianthoides generally has longer petioles, has smaller heads on shorter peduncles, and occupies less-open habitats than var. scabra.