4. Helenium virginicum S.F. Blake (Virginia sneezeweed)

Map 1187

Plants perennial herbs, with fibrous roots. Stems erect or ascending, 10–150 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 to densely dotted with sessile to impressed, yellow glands. Basal and lowermost stem leaves present at flowering, significantly larger than the median stem leaves (to 18 cm long), the blade narrowly oblanceolate to oblanceolate, unlobed or with few to several shallow, rounded, pinnate lobes. Median and upper stem leaves 2–12 cm long, narrowly oblong to narrowly oblanceolate or narrowly lanceolate, unlobed, the margins entire or few-toothed, tapered at the base, long-decurrent as narrow wings of green tissue along the stem, angled or tapered to a sharply pointed tip. Involucre 6–15 mm long, 8–16 mm in diameter, the outer series of involucral bracts fused at the base, the midnerve inconspicuous or sometimes somewhat thickened (keeled), the outer surface sparsely to moderately pubescent with minute, curved hairs, also moderately gland-dotted. Ray florets 8–13, pistillate (with a 2-branched style exserted from the short tube at flowering and a well-developed ovary that potentially develops into a fruit), the corolla 5–20 mm long, yellow, rarely brownish- or reddish-tinged toward the base. Disc florets with the corolla 2.5–3.5 mm long, yellow, 5-lobed. Pappus of 5(6) scales, 0.6–1.5 mm long, the awned tip relatively long. Fruits 1.8–2.5 mm long, narrowly wedge-shaped, with (5–)8 blunt, orangish tan ribs, the surface light brown, moderately to densely pubescent with white to straw-colored hairs, mostly along the ribs, also with often inconspicuous, moderate, yellow to orange, sessile glands. 2n=28. July–October.

Uncommon in the south-central portion of the Ozark Division, most abundant in Howell County (Missouri, Virginia). Sinkhole ponds and moist swales of upland prairies; also pastures, ditches, roadsides, and moist, open, disturbed areas.

For many years, this species was thought to be endemic to a series of sinkhole pond margins in and adjacent to the Piedmont of Virginia. Steyermark (1960) first observed the Missouri plants at a single site in Howell County, but he considered them to represent a putative hybrid between H. autumnale and H. flexuosum, which were both growing in the immediate vicinity. That hybrid, however, differs in a number of morphological features and is sterile. Beginning in the mid-1980s, John Knox of Washington and Lee University began studying the ecology, breeding system, and taxonomy of H. virginicum and stumbled upon Steyermark’s specimen during the course of herbarium searches. In a series of studies (Knox, 1987, 1997; Knox et al., 1995; Messmore and Knox, 1997; Simurda and Knox, 2000; Simurda et al., 2005), Knox and his colleagues established that H. virginicum is a species separate from H. autumnale and H. flexuosum, that it is not a hybrid involving those two species, and that the Missouri populations appear to represent the same species as the populations in Virginia. In 1998, H. virginicum was listed as Threatened under the Federal Endangered Species Act, and Missouri was added to the designated range of the species at about the time of publication of the Draft Recovery Plan developed by a committee under the authority of the U.S. Fish and Wildlife Service (Van Alstine, 2000). One of the actions recommended in this plan was for further inventory. Subsequent fieldwork in southern Missouri by Rhonda Rimer and Bill Summers of the Missouri Department of Conservation beginning in 2003 resulted in the discovery of about 30 additional populations in south-central Missouri. Thus far, no plants have been discovered in states between Missouri and Virginia, but inventory efforts will likely continue in the future.