Schweinitz's Sunflower

Helianthus schweinitzii

Description

Schweinitz's sunflower, Helianthus schweinitzii, is a rhizomatous perennial herb that grows from 3.3-6.6 ft (1-2 m) tall from a cluster of carrot-like tuberous roots. Stems are usually solitary, branching only at or above mid-stem, with the branches departing from the stem at about a 45° angle. The stem is usually pubescent but can be nearly glabrous; it is often purple. The leaves are opposite on the lower stem, changing to alternate above. In shape, they are lanceolate, wider near their bases, but variable in size, being generally larger on the lower stem, and gradually reduced upwards. Lower stem leaves average 3.9-7.8 in (10-20 cm) long and 0.6-0.9 in (1.5-2.5 cm) wide—about five to 10 times as long as wide. Upper stem leaves (subtending branches of the inflorescence) average about 2 in (5 cm) long and 0.4 in (1 cm) wide. Leaf margins are entire or with a few obscure serrations and are generally also somewhat revolute. Texture of the leaves is rather thick and stiff. The pubescence of the leaves is distinctive and is one of the best characters to distinguish Schweinitz's sunflower from its relatives. The upper surface of the leaves is rough, with the broad-based spinose hairs directed toward the tip of the leaf. The lower surface is more or less densely pubescent, with soft white hairs obscuring the leaf surface. From September to frost, Schweinitz's sunflower blooms with comparatively small heads of yellow flowers. The nutlets are approximately 0.1 in (3.3-3.5 mm) long and are glabrous with rounded tips.

The following combination of characters separates H. schweinitzii from all other eastern North American species in the genus: heads small (the involucre less than 0.4 in or 1 cm across), stems at least sparsely strigose or hirsute below the inflorescence, leaves sessile to short-petiolate less than 0.6 in (1.5 cm) long, very rarely to lanceolate, broadest near base, five to 10 times as long as wide.

Habitat

The species occurs in clearings and edges of upland woods on moist to dryish clays, clay-loams, or sandy clay-loams that often have a high gravel content and are moderately podzolized. The underlying rock types are highly weatherable, generally contain low amounts of resistant minerals such as quartz, and generally weather to fine-textured soils. Schweinitz's sunflower usually grows in open habitats not typical of the current general landscape in the piedmont of the Carolinas. Some of the associated species, many of which are also rare, have affinities to glade and prairie habitats of the Midwest. Other species are associated with fire-maintained sandhills and savannahs of the Atlantic Coastal Plain and piedmont. The habitat of this sunflower tends to be dominated by members of the aster, pea, and grass families, an association emphasizing affinities of the habitat to both longleaf pine-dominated sandhills and savannahs of the southeastern coastal plain and to glades, barrens, and prairies of the Midwest and Plains.

Distribution

Schweinitz's sunflower is endemic to the piedmont of the Carolinas, where it is currently known from 10 populations in North Carolina and six in South Carolina. The North Carolina populations are located in Union, Stanly, Cabarrus, Mecklenberg, and Rowan Counties. The species has been extirpated from Stokes and Montgomery Counties in North Carolina. All the extant and historic sites for the species in South Carolina are in York County. Thirty-eight percent of the historically extant populations have been destroyed. Most of the remaining populations are small, with four of them containing less than 40 individuals each.

Threats

Ten of the remaining populations survive along roadsides and three others are within utility line rights-of-way. Three others have been partially bulldozed in recent years. All of these populations are small, which increases their vulnerability to extirpation as a result of highway and right-of-way maintenance and improvement, particularly if herbicides are used. Significant declines have been noted within the last three years in six of the remaining populations with decreases ranging from 9-89%. An unusually vigorous population and one of the few that has exhibited increases in recent years is located on a highly vulnerable site only a few feet (1 ft=0.3 m) away from the edge of a paved highway. The limited geographic range and scarcity of seed sources, as well as appropriate habitat, increases the severity of the threats to Schweinitz's sunflower. The species requires some form of disturbance (probably provided historically by fire and/or native grazing animals) to maintain its open habitat. However, repeated mowing during the flowering and fruiting season, as has happened to several North Carolina roadside populations in recent years, further endangers the species. Many of the remaining populations are also threatened due to residential and commercial expansion, and by the invasions of aggressive exotics including Ligustrum sinense (privet).

Conservation and Recovery

The U. S. Fish and Wildlife Service and the North Carolina Natural Heritage Program are continuing to try to work with the Departments of Transportation in North and South Carolina to protect roadside populations. To date, these efforts have been almost totally unsuccessful. In North Carolina, one population and part of another are on land managed by the Nature Conservancy. Limited protection is provided to a third population through a management agreement with the private landowners. The Nature Conservancy initiated a prescribed burning program for its sites in 1992. None of the South Carolina sites has any formal protection, but utility companies have been contacted regarding the presence of the species within their rights-of-way. The North Carolina Botanical Garden has initiated seed collections from all the North Carolina populations, following the Center for Plant Conservation's guidelines for ex situ conservation of genetic material.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

U. S. Fish and Wildlife Service
Asheville Ecological Services Field Office
160 Zillicoa St.
Asheville, North Carolina 28801-1082
Telephone: (828) 258-3939
Fax: (828) 258-5330

References

Radford, A., H. Ahles, and C. Bell, 1984. Manual of the Vascular Flora of the Carolinas. University of North Carolina Press, Chapel Hill, pp. 1111-1118.

U. S. Fish and Wildlife Service. 7 May 1991. "Determination of Endangered Status for Schweinitz's Sunflower (Helianthus schweinitzii )." Federal Register 56 .

Weakley, A., and R. Houk. 1992. "Technical Draft Recovery Plan for Schweinitz's Sunflower (Helianthus schweinitzii )." U. S. Fish and Wildlife Service, Atlanta, Georgia, 37 pp.