13. Helianthus salicifolius A. Dietr. (willow-leaved sunflower)

Pl. 280 c, d; Map 1200

Plants perennial herbs, with long-creeping, branched rhizomes, often occurring as colonies of stems. Stems not densely clumped, 50–200(–250) cm long, glabrous, often somewhat glaucous. Leaves numerous (sometimes appearing in irregular fascicles) and well developed along the stem (usually many more than 30 nodes), mostly alternate, sessile or nearly so, often appearing arched or drooping. Blades of the stem leaves 4–20 cm long, 0.1–1.0 cm wide, linear or those of the lowermost leaves sometimes narrowly lanceolate (mostly 12–20 times as long as wide), not folded longitudinally, tapered at the base, tapered to a sharply pointed tip, the margins entire, mostly curled under, the surfaces glabrous or sparsely pubescent with minute, slender, soft, appressed hairs, also with moderate to dense, sessile, yellow to brown glands, with 1 main vein. Inflorescences of solitary terminal heads or more commonly appearing as open, few-headed clusters or open panicles, the heads mostly long-stalked. Involucre 9–14 mm long, 10–18 mm in diameter, mostly extending beyond the tips of the disc corollas, the bracts in 2 or 3 subequal series, narrowly lanceolate to nearly linear, tapered to a sharply pointed, slender, loosely ascending to more commonly spreading or recurved tip, the margins with a dense fringe of short hairs, the surfaces glabrous or inconspicuously and minutely hairy and often also with scattered, sessile, yellow glands. Receptacle shallowly convex, the chaffy bracts 6–9 mm long, oblong-oblanceolate, tapered to a sharply pointed, green, minutely hairy tip, the outer surface also minutely hairy. Ray florets 10–21, the corolla 2.5–3.5 cm long, glabrous. Disc florets with the corolla 5–6 mm long, the lobes and sometimes also the tip of the tube reddish brown to dark purple above a yellow basal portion. Pappus of 2 scales 3.0–3.5 mm long, these oblong-lanceolate, tapered abruptly to a sharply pointed, minutely awnlike tip, often with an additional pair of thin, irregular apical lobes, also usually with 2–6 additional minute, oblong scales 0.2–0.5 mm long. Fruits 4–6 mm long, narrowly wedge-shaped, flattened but 4-angled in cross-section, the surface glabrous, often finely mottled with dark brown and lighter brown patches. 2n=34. August–October.

Scattered in the Unglaciated Plains Division north locally to Jackson County; introduced in Scott County (Texas, Oklahoma, Kansas, and Missouri; introduced sporadically farther north and east). Upland prairies and rarely sand prairies and calcareous glades; also roadsides.

In recent years, this species has become available as an ornamental through native plant nurseries. In its native habitat, the plants generally grow in rather poor, dry soils. Gardeners who grow willow-leaved sunflowers under typical garden conditions may be surprised when the plants produce numerous stems more than 4 m long. The species also may spread aggressively by rhizomes and seeds. Finches and other seed-eating birds relish the achenes.