Swertia caroliniensis (Gentianaceae) in Pontotoc, Lee, and Chickasaw Counties in Mississippi.

M. B. Huneycutt [1]

Swertia caroliniensis (Walt.) Kuntze (Gentianaceae), commonly called American columbo (Hemmerly, 1990), or columbo, is a robust, monocarpic, glabrous perennial with erect stems ranging from one to three meters tall and two to three centimeters in diameter. It has thick tuberous roots and leaves in whorls of three to nine. The inflorescence is a panicle of cymes. There are four calyx lobes. The four corolla lobes are separate nearly to the bases, rotate, yellowish to whitish, and streaked with green. Each corolla lobe has a prominent, elliptic to obovate, green gland toward the base. There are four stamens and the fruit is a capsule (Radford et al., 1968). A member of the Gentianaceae family, the genus Swertia L. includes numerous tall, showy herbs.

One population of 30-40 plants and a smaller population of 10-12 plants of Swertia caroliniensis were found in Trace State Park in Pontotoc County, Mississippi (Floyd, 1995). In Lee County one mile east of the Pontotoc-Lee County Line and within four and one half miles of Trace State Park a third population of several dozen plants was observed. Three additional populations were observed in Chickasaw County within the Tombigbee National Forest.

The larger population within Trace State Park was first observed in June, 1993, at the base of a calcareous slope. It was situated in an ecotone where the mixed forested habitat of the slope abruptly met a mowed meadow at its' base. At that time several plants had basal leaves and one plant retained an inflorescence in which the panicle of cymes had begun to deteriorate. The inflorescence, however, still presented a showy appearance. If not for this single plant in flower the entire population might have been overlooked.

We returned to the site in June, 1994, to once again discover a thriving population of 30-40 plants, which extended several meters upward from the base of the slope. Numerous observations of the population were made between June and September, 1994. The basal leaves remained, yet none of the plants flowered during this period.

The smaller population was first observed in the spring of 1995. It contained 10-12 plants with only two plants showing indications of flowering.

The Lee County population was first observed by us in 1994. It consisted of several dozen plants in all states of development including at least nine in flower.

Two Chickasaw County populations within the Tombigbee National Forest were observed in the spring of 1995. One population was found on the south side of Davis Lake and another smaller population was found in dry deciduous woods off County Road #123. Both populations contained flowering and fruiting plants. The third and largest of the Chickasaw County populations was observed in June, 1997, in the Chuquatonchee Research Natural Area north of Davis Lake. McDaniel (1992) lists two sites for Swertia caroliniensis elsewhere in the Tombigbee National Forest with one consisting of over 8000 plants.

A further search of the literature revealed records of its occurrence in Monroe County (MacDonald, 1996). The IBE Collection at Mississippi State University Herbarium contains records from Chickasaw, Lee, Monroe, Noxubee, and Oktibbeha Counties (John MacDonald, graduate student, Mississippi State University, personal communication). The Mississippi Natural Heritage Program provided records of sites in five additional counties, not previously mentioned, including Hinds, Lowndes, Madison, Union, and Winston (Ron Wieland, ecologist, Mississippi Natural Heritage Program, personal communication).

Trace State Park along with our other sites is located within the Pontotoc Ridge Physiographic Region of the state (Fig. 1). The Pontotoc Ridge Region consists of a series of parallel ridges twelve to fourteen miles wide. It occupies the western third of Alcorn County and the eastern half of Tippah County widening to the northern boundary of Union County. It passes east of Union County's center in a strip less than two townships wide and continues to narrow through Pontotoc and Chickasaw Counties terminating in a point near Houston, Mississippi (Lowe, 1919; Floyd, 1995).

All of our populations described here were found growing in soils underlain with calcareous materials leading us to assume that it grows in circumneutral soils. Steyermark (1963) indicates that in Missouri Swertia caroliniensis occurs in rich, low, or rocky open woods and thickets, often in ravine bottoms and wooded valleys along streams in acidic soils. Radford, Ahles, and Bell (1968) state simply that the species grows in "woodlands." Lowe (1921) states that it occurs in rich upland forests.

According to Hemmerly (1990), Swertia caroliniensis is a triennial which produces a rosette of large smooth leaves for two growing seasons before producing a panicle in the third year. The failure of the plants to flower during the 1994 season may be attributed to this characteristic. However, Steyermark (1963) describes the plants as perennials that may live several years without flowering. Our observations agree with Steyermark's conclusion. We have noted basal rosettes more than three years old which showed no flower stalks in the third year.

Swertia caroliniensis is the only representative of the genus Swertia in the eastern United States (Hemmerly, 1990). It is considered secure globally, though possibly rare in some parts of the range (MNHP, 1992; MNHP, 1997). It is relatively rare, but widespread, in the eastern United States, preferring limestone soil (Hemmerly, 1990). Swertia caroliniensis is considered rare or uncommon and vulnerable to extinction within Mississippi (MNHP, 1992; MNHP 1997). The Thomas M. Pullen Herbarium (MISS) at the University of Mississippi had no specimens of Swertia caroliniensis prior to this collection. McDaniel (1992) indicates that a study of the biology of Swertia caroliniensis would be useful to determine factors including flowering and fruiting.

ACKNOWLEDGMENTS

The authors wish to thank the Mississippi Natural Heritage Program for funding the plant survey of Trace State Park. We also appreciate the cooperation and assistance of Mr. Jim Pickett, former manager of Trace State Park, and his staff. Thanks also to John MacDonald and Ron Wieland for providing data on additional sites.

(1.) Author for correspondence.

LITERATURE CITED

Floyd, M.D. 1995. The Vascular Flora of Trace State Park. M.S. Thesis. University of Mississippi, University, MS. 112 pp.

Hemmerly, T.E. 1990. Wildflowers of the Central South. Vanderbilt University Press, Nashville, TN. 121 pp.

Lowe, E.N. 1919. Mississippi, its geology, geography, soils and mineral resources. Mississippi State Geol. Surv. Bull. No. 14. 346 pp.

Lowe, E.N. 1921. Plants of Mississippi: A list of flowering plants and ferns. Mississippi State Geol. Surv. Bull. No. 17. 292 pp.

MacDonald, J. 1996. A survey of the flora of Monroe County Mississippi. M.S. Thesis. Mississippi State University, Mississippi State, MS. 163 pp.

Mississippi Natural Heritage Program (MNHP). 1992. Special Plant List. Museum of Natural Science, Mississippi Department of Wildlife, Fisheries & Parks. Jackson, MS. 7 pp.

Mississippi Natural Heritage Program (MNHP). 1997. Special Plant List. Museum of Natural Science, Mississippi Department of Wildlife, Fisheries & Parks. Jackson, MS. 12 pp.

McDaniel, S. 1992. Sensitive Plants of the Tombigbee National Forest (Tombigbee District). Institute for Botanical Exploration, Box EN, Mississippi State, MS 39762. 52 pp.

Radford, A.E., H.E. Ahles, and C.R. Bell. 1968. Manual of the Vascular Flora of the Carolinas. The University of North Carolina Press, Chapel Hill, N.C. 1183 pp.

Steyermark, J. A. 1963. Flora of Missouri. The Iowa State University Press, Ames. 1728 pp.

Temple, L.C., and T.M. Pullen. 1968. A preliminary checklist of the Compositae of Mississippi. Castanea 33:106-115.