Perennials, to 200 cm (rhizomatous, rhizomes stout). Stems densely hirsute (hairs mostly antrorse, to 0.5 mm). Leaves: blades ovate to elliptic (not lobed), margins denticulate to serrate, apices acute to obtuse or acuminate, faces densely hirsute and gland-dotted (glands fewer adaxially); basal 15-30 × 3-10 cm, bases attenuate; cauline petiolate, ovate to elliptic, proximal 3-25 × 1-15 cm, usually 3-5-lobed, bases truncate to cuneate or rounded. Heads (8-25) in loose, corymbiform to paniculiform arrays. Phyllaries to 1.5 cm (faces hairy and ± gland-dotted). Receptacles conic to hemispheric; paleae 4-6 mm, apices acute, abaxial tips hirsute and gland-dotted. Ray florets 10-16; laminae (yellow to yellow-orange) linear to oblanceolate, 20-40 × 5-8 mm, abaxially sparsely hairy, abundantly gland-dotted. Discs 10-17 × 5-15 mm. Disc florets 200-400+; corollas yellowish green on basal 1/2, otherwise brown-purple, 3-4.2 mm; style branches ca. 1 mm, apices acute. Cypselae 2-3.5 mm; pappi coroniform, to ca. 0.2 mm. 2n = 38. Flowering late summer-fall. Mesic to wet prairies, stream banks, and woodland openings; 20-300 m; Ark., Conn., Ill., Ind., Iowa, Kans., Ky., La., Mass., Mich., Miss., Mo., N.Y., N.C., Okla., Tenn., Tex., Wis. Rudbeckia subtomentosa is often cultivated as an ornamental.
From Flora of Indiana (1940) by Charles C. Deam
Infrequent in rather wet prairie habitats in the northwestern part of the state, mostly along roadsides; and in the southwestern part of the state in low, open woods, where it is usually associated with prairie plants.
Perennial from a stout rhizome; stem 6-20 dm, glabrous below, ±densely short-hairy above; lvs firm, densely short-hairy, especially beneath, ovate to sometimes lance-elliptic, petiolate, serrate, generally some of the larger ones deeply trilobed; disk dark purple or brown, 8-16 mm wide, not elongating; rays 12-21, yellow, 2-4 cm; receptacular bracts obtuse or acutish, distally viscidulous-canescent; pappus a minute crown; 2n=38. Prairies and low ground; Mich. to Wis., s. to w. Tenn., La., and Okla. July-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.