8. Helianthus microcephalus Torr. & A. Gray (small woodland sunflower)

Pl. 281 a, b; Map 1195

Plants perennial herbs, lacking rhizomes or with short, thick rhizomes, often occurring as clumps. Stems usually few to several, 50–250(–450) cm long, glabrous below the inflorescence, often somewhat glaucous. Leaves well developed along the stem (usually with 8–20 nodes), gradually reduced toward the stem tip, all or mostly opposite, mostly with a short petiole less than 4 cm long. Leaf blades 4–18 cm long, 1–6 cm wide, relatively thick-textured, lanceolate to narrowly ovate (mostly 4–9 times as long as wide), flat, not folded longitudinally, rounded to short-tapered at the base, tapered to a sharply pointed tip, the margins finely toothed to nearly entire, flat, the upper surface strongly roughened with moderate, minute, stout, broad-based hairs, the undersurface moderately to densely pubescent with short, softer, loosely appressed hairs and also with sparse to moderate, sessile, yellow glands, with 3 main veins, the lateral pair branching from the midnerve well above the base of the blade, arching upward. Inflorescences appearing as open clusters or more commonly open panicles. Involucre 5–7 mm long, 8–10 mm in diameter, about as long as or slightly longer than the tips of the disc corollas, the bracts in 3 or 4 more or less subequal, overlapping series, narrowly lanceolate, tapered to a sharply pointed, loosely ascending to spreading or recurved tip, the margins with a fringe of short, spreading to ascending hairs, the outer surface glabrous or sparsely hairy toward the base but usually lacking glands. Receptacle convex to short-conical, the chaffy bracts 5–7 mm long, narrowly oblong to narrowly oblong-oblanceolate, with 3 short-tapered, sharply pointed lobes at the tip, these straw-colored or rarely purplish-tinged, the outer surface minutely hairy toward the tip. Ray florets 5–8, the corolla 1.0–1.5 cm long, the outer surface usually with sparse, sessile, yellow glands. Disc florets with the corolla 4.0–5.5 mm long, the corollas yellow, the lobes minutely hairy on the outer surface. Pappus of 2 scales 1.5–2.5 mm long, these lanceolate to narrowly triangular, tapered to a sharply pointed, often minutely awnlike tip. Fruits 3.5–4.5 mm long, wedge-shaped to narrowly obovate, only slightly flattened but more or less bluntly 4-angled in cross-section, the surface glabrous, with fine, darker and lighter brown mottling. 2n=34. August–September.

Uncommon in the Crowley’s Ridge Section of the Mississippi Lowlands Division and the adjacent eastern portion of the Ozarks (eastern U.S. west to Minnesota and Louisiana). Mesic upland forests, banks of streams, and margins of acid seeps; rarely also old fields.

Heiser et al. (1969) noted that this species hybridizes with H. divaricatus (such hybrids have been called H. ×glaucus Small); such hybrids have not been reported for Missouri but might be found in the state in the future.