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). 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.
Robust, fibrous-rooted perennial 5-15 dm; lvs ovate or lance- ovate, often subtruncate at base, serrate, 5-15 נ2.5-8 cm, on petioles 5-35 mm; heads naked-pedunculate, the disk 1-2.5 cm wide; rays 8-16, rather pale yellow, 1.5-4 cm; achenes essentially glabrous; 2n=28. Rich to dry woods, prairies, and waste places; Que. to B.C., s. to Ga. and N.M. July-Oct. Var. helianthoides, with glabrous, often glaucous stem and rather thin lvs smooth on both sides or merely slightly scabrous above, occurs from N.Y. to Mich. and Ill., and s. to Ga. and Miss. Var. scabra (Dunal) Fernald, with firmer lvs scabrous on both sides, the stem often scabrous as well, occurs in the Great Plains and prairie region, and e. across the n. part of our range to the Atlantic. (H. scabra)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.