Tennessee Purple Coneflower
Tennessee Purple Coneflower
|Listed||June 6, 1979|
|Description||Pale purple, ray flowers with a central disk.|
|Habitat||Cedar glades in forest openings.|
|Threats||Residential and commercial development; competition.|
Tennessee purple coneflower, Echinacea tennesseensis, normally grows 3 ft (0.9 m) or more in height and bears pale purple, ray flowers with a central disk, similar to daisies. Sharp-tipped bracts cause the flower to resemble a hedgehog, the Greek word for which, echinos, furnishes the genus name. Leaves grow from the base of the stem, which usually bears a single flower head. The roots are strong and fibrous. Flowers produce a small number of large seeds that do not adhere to animal fur and are not easily dispersed by common methods such as wind and water.
Tennessee purple coneflower grows in cedar glades, usually dominated by red cedar, in forest openings where bedrock is exposed or covered by a very thin layer of soil. The impenetrable bedrock often forces coneflower roots to grow horizontally. It is a harsh environment, with extremes in light, temperature, and moisture. In summer, glade temperatures can be considerably hotter than in the surrounding forest. To survive in open glades, coneflowers must be able to compete successfully for scarce moisture, and drought places them under considerable stress. Juvenile plants whose roots are less than 6-8 in (15-20 cm) long are the most vulnerable during dry conditions.
The factors that adapt the Tennessee coneflower to a glade habitat may limit it elsewhere. For example, its stout fibrous taproots restrict vegetative reproduction, and its slow growth gives it a disadvantage in competition with fast-growing plants, which can shade or crowd out the coneflower. It is seldom seen growing in habitat where there is more than 50% shade, and competition for water and light exclude it from areas with taller, denser vegetation.
The Tennessee purple coneflower is believed to have always been limited to its present central Tennessee range, although it was once probably more abundant there. A Rutherford County site surveyed in 1967 was developed for a trailer park sometime after its discovery. Two colonies in Davidson County, near Moss Spring Drive, discovered in 1972, were destroyed by residential development prior to 1975. There has been one unconfirmed report of Tennessee purple coneflower in Arkansas.
It is probable that in the distant past, coneflower distribution was continuous, and the Tennessee colonies were linked to those in the Midwestern prairies, where other coneflower species are common.
There are now five known Tennessee purple coneflower populations, all located in cedar glades within a 14-mi (5.6-hectare) area in the central Tennessee counties of Davidson, Rutherford, and Wilson. In 1988, the number of individual plants at each site varied from 3,700 to 89,000. One population that has two distinct colonies about 0.3 mi (0.5 km) apart is considered to be a single population because of the potential for gene exchange. However, the five populations are each more than 3.5 mi (5.6 km) apart and are considered to be distinct because cross-pollination by insects is unlikely.
Loss of habitat to residential and industrial development and to road construction has been the primary threat to this coneflower. Limited disturbance may benefit the plant, but intensive habitat alteration, such as plowing fields and clear-cutting, eliminates the flower altogether. The outright destruction of glades by paving, building, and establishing lawns has destroyed a number of coneflower colonies.
The specialized nature in some of the characteristics that make Tennessee coneflower well adapted to the glade environment might also be inhibiting its escape from the glades or growth in other habitats. By having stout fibrous taproots, they have forfeited the ability to spread vegetatively by rhizomes, stolons, or other asexual means of propagation. Likewise, by slowly growing a short, woody stalk, they are poorly evolved for competing with tall, fast-growing taxa that can shade or crowd them. It is also conceivable that their narrow hairy leaves or stomatal arrangements could be ill-suited for adequate photosynthetic productivity under shadier or moister regimes.
Conservation and Recovery
At present no state laws prohibit taking of endangered plants from private land in Tennessee. Though sympathetic, landowners have been recalcitrant about granting easements or signing management agreements. One owner of an industrial facility that has a coneflower population of over 100 plants has fenced the area around the plants and cleared away debris.
Recovery will depend on negotiating agreements with the landowners to allow cooperative management or registration of sites as natural areas. Three colonies survive on state lands managed by the Division of Forestry, which has agreed to manage the areas to preserve the coneflower.
Coneflowers are now being cultivated at the Tennessee Valley Authority Nursery and are being distributed to such facilities as Cheekwood Botanical Garden and the Warner Nature Center, both in Nashville. A number of private landowners have obtained seeds from the coneflower and have grown it successfully in home gardens. The Tennessee Native Plants Society has also dispensed coneflower seed to private landowners who have grown it successfully in their home gardens. Eventually, new areas will be seeded to expand the current distribution of the plant.
Several attempts to establish new colonies in natural settings or additional plants in an existing colony have been made. Three new experimental plantings have been established. Two of them are within existing colonies and are treated as satellites of the colony; the third experimental planting is a new colony started at Stone's River National Battlefield, and is now a healthy population of several hundred plants. A member of the Tennessee Native Plants Society established a small colony of plants on her glade property. The plants are regularly monitored and are protected as a regional natural area. The department has made several attempts to establish new colonies on Cedars of Lebanon State Forest. Only one of five of these attempts has been successful.
U.S. Fish and Wildlife Service
Division of Endangered Species
1875 Century Blvd. Ste 200
Atlanta, Georgia 30345
Hemmerly, T. E. 1976. "Life Cycle Strategy of a Highly Endemic Cedar Glade Species: Echinacea tennesseensis (Compositae)." Ph.D. Dissertation. Vanderbilt University, Nashville.
McGregor, R. L. 1963. "The Taxonomy of the Genus Echinacea (Compositae)." University of Kansas Science Bulletin 48:113-142.
U.S. Fish and Wildlife Service. 1983. "Tennessee Coneflower Recovery Plan." U.S. Fish and Wildlife Service, Atlanta.