3. Helenium flexuosum Raf. (southern sneezeweed, purple-headed sneezeweed)

Pl. 279 h, i; Map 1186

Plants perennial herbs, with fibrous roots. Stems erect or ascending, 20–120 cm long, few- to many-branched above the midpoint, narrowly several-winged, glabrous or sparsely to moderately pubescent with short, sometimes curved or curled, more or less spreading to loosely ascending hairs, also moderately dotted with sessile to impressed, yellow glands. Leaves glabrous or sparsely to moderately pubescent with short, sometimes curved, mostly spreading hairs, also moderately dotted with sessile to impressed, yellow glands. Basal and lowermost stem leaves absent or withered at flowering, not or only slightly smaller than the median stem leaves, the blade narrowly oblanceolate to less commonly narrowly obovate, unlobed or with few to several shallow, rounded, pinnate lobes. Median and upper stem leaves 3–12 cm long, narrowly oblanceolate to oblong-oblanceolate, unlobed, the margins entire or few-toothed (often only above the midpoint), somewhat tapered at the base, long-decurrent as narrow wings of green tissue along the stem, angled or tapered to a usually sharply pointed tip. Involucre 6–18 mm long, 8–18 mm in diameter, the outer series of involucral bracts fused at the base, the midnerve inconspicuous or sometimes somewhat thickened (keeled), the outer surface moderately to densely pubescent with minute, curved hairs, also moderately gland-dotted. Ray florets 8–13 (occasionally absent elsewhere), sterile (lacking stamens and style at flowering and with an ovary that is shorter and thinner than those of the disc florets, not developing into a fruit), the corolla 5–20 mm long, yellow, occasionally with reddish streaks or reddish-tinged toward the base. Disc florets with the corolla 2.5–4.0 mm long, reddish brown to dark purple, usually 4-lobed. Pappus of 5(6) scales, 0.8–2.0 mm long, the awned tip relatively long. Fruits 1.0–1.7 mm long, wedge-shaped, with 5 ribs, the surface brown but this obscured by the often dense, sessile, yellow glands, the ribs moderately to densely pubescent with white hairs. 2n=28. June–November.

Scattered, mostly south of the Missouri River (eastern U.S. west to Wisconsin and Texas; Canada). Banks of streams, rivers, and spring branches, margins of sinkhole ponds, sloughs, swamps, bottomland prairies, moist depressions of upland prairies, bottomland forests, and seepy ledges of bluffs; also pastures, old fields, ditches, railroads, roadsides, and moist, open, disturbed areas.

Although no voucher specimens have been collected thus far, John Knox (personal communication) of Washington and Lee University has reported observing rare hybrids between H. flexuosum and H. autumnale in 1994 from a pasture adjacent to a stream in Shannon County. These hybrids had well-developed but relatively narrow stem leaves and dark-colored disc corollas, and they were sterile. The two species grow in proximity often enough that such hybrids should be searched for in the future. Helenium flexuosum frequently also grows in proximity to H. virginicum. A possible hybrid between these two species was collected in 2003 by Bill Summers from a mixed population in Howell County. This unusual specimen had somewhat reduced median and upper leaves and disc corollas with a greenish tube and 4 brownish purple lobes. However, it appeared to be developing at least some fully formed fruits, so it may represent merely a depauperate individual of H. flexuosum.