Schweinitz's Sunflower - Helianthus schweinitzii
Contributed by Robert Siler, SCWF Member
One of the rarest species in the nation, Schweinitz's sunflower has been on the US Fish and Wildlife Service's federally endangered list since June 1991 (Department of Interior 1991). Found only in the Carolinas' lower Piedmont, populations occur in Lancaster and York County in South Carolina and Anson, Cabarrus, Davidson, Gaston, Mecklenberg, Montgomery, Randolph, Rowan, Stanly and Union Counties in North Carolina - all within about 90 miles surrounding Charlotte. In these areas combined, only 90 known populations exist; less than 10 sites are protected (Dr. Richard Houk, Rock Hill, SC, personal communications).
The rare flower was named after Lewis David von Schweinitz (1780-1834), a Moravian clergyman and church administrator from Salem, N.C., who discovered the sunflower in the early 1800s. Often called the founder of American mycology, Schweinitz published The Fungi of North Carolina in 1818 (The New York Botanical Garden 1999). Schweinitz also collaborated with many of the early botanist, including John Torrey. Later, in 1841, John Torrey and Asa Gray (Department of Interior 1991) described and named the sunflower from material collected in North Carolina, presumably from Schweinitz.
Schweinitz's sunflower blooms late, from August to frost. The flower is composed of relatively small, yellow disk flowers (center portion) and yellow ray flowers ("petals" surrounding the center). The plant generally ranges from 3-6 feet tall but grows as tall as 16 feet. The composite flowers are 2-3 inches in diameter. The leaves of the lower stem are generally less than 1-inch wide with upper stem leaves less than half that wide. Leaves range from 2-8 inches long with the upper side being rough and the lower side "hairy". The stem is usually covered with minute bristles or hairs and is reddish-purple (USFWS 1994). From a distance, the sunflower resembles many of the yellow fall asters that you see in roadside Carolina ditches and fields. The main difference is that Schweinitz's sunflower is generally taller that most of the late summer/fall asters and sunflowers. The head (disk) is small (1/4 to 2/3 inches in diameter) - not nearly the size of sunflowers cultivated for oil or gardens.
Geology and soil appears to have a lot to do with the restricted distribution of the species. Sites often have shallow soils and exposed boulders and bedrock. Soils are generally fine textured and tend to shrink and swell with soil moisture, fissuring when dry. These soils present harsh conditions for many plant species and are not widely used for agriculture or forestry. Schweinitz's sunflower requires disturbance and openings and will flourish under sparse canopies with abundant sunlight. That's why the plant is most abundant on unforested roadsides, electric-line corridors and other permanently maintained openings. Sunflower populations dwindle as trees colonize their habitats, since they don't fare as well when shaded by taller vegetation. The common habitat of Schweinitz's sunflower, if left undisturbed, tends to succeed to a blackjack and post oak community. This vegetation type is often referred to as the Blackjacks because of the abundance of blackjack oaks. Trees on these sites grow slowly and occur at low or moderate densities. When disturbed or cleared, the plant community resembles a midwestern prairie. In fact, plant species associated with the sunflower are uncommon or rare in the Carolinas but characteristic of the prairies and glades of the Midwest. An especially notable site is the "Rock Hill Blackjacks" near Rock Hill, S.C. When disturbed, these sites display an abundant and diverse wildflower community with many of the Midwest prairie-type plants. In early accounts, John Henry Logan (1859) must have been describing this area: extensive prairie ridges, widely spaced large trees, great stands of cane, wildflowers of every hue and large herds of buffalo and elk in Richland, Fairfield, Chester and York Counties. Douglas S. Brown (1953) reported writings of Mrs. Elizabeth F. Ellet and others that describe the blackjack lands of Chester and York as once being open prairies "where a person could be seen at a great distance" but by the 1800s, were thickly covered with blackjack oak.
The discovery of the plant diversity of the Rock Hill Blackjacks is a story in itself. In 1982, a Duke Power biologist, who is a board member of SC Wildlife Federation, and a forester were setting up test plots to use herbicides on a right-of-way because the rocky land was difficult to bush-hog. The biologist noticed plants he recognized from his years with the Illinois Department of Conservation and contacted the SC Department of Natural Resources. The South Carolina Heritage Trust Program inventoried the plants and later acquired lands in the Rock Hill Blackjacks. The SC Heritage Trust restored the prairie habitat of their purchase, which has resulted in unique plant communities and an abundance of Schweinitz's sunflowers.