Perennials, 20-200 cm (with crown buds). Stems erect, glabrous. Leaves cauline; opposite or alternate; petioles 0.3-3 cm; blades (greenish, at least abaxially, 3-nerved at bases) lanceolate, 7.2-15.5 × 1.3-4 cm, bases cuneate, margins entire or serrate, abaxial faces tomentulose, densely gland-dotted. Heads (1-)3-15+. Peduncles 1-3(-8) cm. Involucres cylindric, 5-7 mm diam. Phyllaries 12-17, lance-linear, 3-6.5 × 1.5-2.5 mm, (margins ciliate) apices acuminate, abaxial faces glabrate, not gland-dotted. Paleae 5-7 mm, 3-toothed (apices hairy). Ray florets 5-8; laminae 10-14 mm. Disc florets 15-22; corollas 4-5.5 mm, lobes yellow; anthers dark, appendages dark. Cypselae 3.5-4.2 mm, glabrous; pappi of 2 aristate scales 1.5-2.2 mm. 2n = 34. Flowering late summer-fall. Open woodlands, shaded roadsides; 10-900 m; Ala., Ark., Conn., D.C., Fla., Ga., Ill., Ind., Iowa, Ky., La., Md., Mich., Minn., Miss., N.J., N.C., Ohio, Pa., S.C., Tenn., Va., W.Va. Helianthus microcephalus is distinguished by its relatively small heads, which have relatively few phyllaries, ray florets, and disc florets, as well as the usually tomentulose abaxial faces of the leaves. Hybrids with H. divaricatus are known.
From Flora of Indiana (1940) by Charles C. Deam
This is strictly a woodland sunflower and is well but sparsely distributed in the southern part of the state. It does not form colonies like most of our sunflowers and usually only a single specimen or a few are found together. Its habitat is a dry or sandy wooded slope, and it is usually associated with black and white oak. It was reported from Porter County by Peattie but I have not seen a verifying specimen.
Fibrous-rooted perennial with crown-buds and a short (seldom over 5 cm) rhizome; stems (0.7-)1-2 m, glabrous and generally glaucous; lvs scabrous above, resinous-dotted and usually also loosely short-hairy beneath, sometimes also glaucous, lanceolate or lance-ovate, 7-15(-20) נ(1-)2-5(-6) cm, toothed or entire, gradually tapering distally, ±abruptly narrowed to the 1-3 cm petiole; upper lvs alternate; heads on long, slender peduncles, small, the yellow disk 0.5-1 cm wide; invol bracts few, lanceolate, acuminate or attenuate, ciliolate, otherwise glabrous or nearly so; rays 5-8, 1-1.5 cm; 2n=34, 68. Woods and brushlands; N.J. to nw. Fla., w. to s. Minn., e. Ark., and se. La. Aug., Sept. (H. glaucus; H. smithii)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.