Eggert's Sunflower

Helianthus eggertii

Description

Eggert's sunflower, Helianthus eggertii, is a perennial member of the aster family (Asteraceae or Compositae) known only from Kentucky, Tennessee, and Alabama. It is a tall (8 ft; 2.4 m) plant arising from a short, thick base, by shallow elongate, fleshy rhizomes that can form an extensive network. The plant is smooth, except for some slight roughening on the upper leaf surfaces, and it has a blue-waxy coloration. The lower leaves are conspicuously whitened. It is distinguished from other sunflowers by its white glaucous stem and underside of the leaves; sessile leaves that taper at the base; and the size of the flower head. It also has a distinctive bluish cast.

The plant's opposite (rarely whorled) leaves are mostly lanceolate to narrowly ovate, the largest being 3.9-5.7 in (9.9-14.5 cm) in length. Leaf edges are smooth or minutely toothed, and the tip is usually pointed. Large yellow flowers 3 in (7.6 cm) wide are borne on the upper third of the stem. Seeds are blackish or grayish and mottled, 0.25 in (0.6 cm) long, faintly striated, and with a few scattered hairs.

Flowering begins in early August and continues through mid-September, and achenes mature from early September to early October; fruit sets between five and 25 seeds per flower head. Seed germination rates are generally low (rarely exceeding 25%), and most require exposure to cold to break dormancy.

Eggert's sunflower develops an extensive rhizome system, and these rhizomes can live for many years. Thus, the plant does not have to produce seeds every year to ensure its survival. If environmental conditions change, such as increased competition or shading, it can survive for several years by vegetative means. It is known to produce viable seeds, but vegetative reproduction is important in plant establishment. The plant produces extensive rhizomes that, optimally, result in the production of dense clusters of stems. Some colonies are reported to be 1,000 sq ft (92.9 sq m). Plants may also be established from seeds within these clumps; therefore, a mix of different individuals can eventually contribute to these extensive patches. For this reason, the number of genetically different individuals in a population is difficult to estimate.

Most non-flowering colonies are found under substantial forest cover, so it is likely that a certain light level is critical to induce flowering. Also, colonies in full sun nearly always produce flowers, some notably more prolific than in heavily forested settings. The role of flower and seed production in the viability of populations is not understood nor are the optimal natural conditions for seedling establishment. However, it is known that perennial sunflowers, including H. eggertii, are self-incompatible. When the number of genetically different individuals in a colony is low, seed set will probably also be low, despite colony size.

Habitat

The natural condition of the barrens/woodland ecosystem where H. eggertii occurs is a mosaic of grassy openings and mixed oak woodlands. Although few good examples of this ecosystem are known to exhibit information on presettlement conditions, it is thought that this community was comprised of stands of small-to medium-sized trees with a semi-open canopy and that the groundcover was nearly continuous with the grassy openings. A combination of drought, periodic fire, edaphic factors, and grazing maintained these habitats. Common trees in this ecosystem, with some variability from north to south in the range, include post oak, southern red oak, red cedar, mockernut hickory, winged elm, and black gum. Grasses with affinities to prairies often dominate the openings in these community complexes, including big blue stem, little blue stem, switchgrass and Indian grass.

Barrens are inherently vulnerable to development because they have a sparse tree cover that allows for easier land clearing and because they are not valued as timberland. Also, the extent and quality of barrens are influenced by periodic fire. With the disruption of normal fire cycles throughout this region, these communities have declined as wild-fires have been controlled.

Although some populations have been discovered on steep rocky slopes in hillside barrens in Davidson County, Tennessee, the predominant habitat for this species is woodland interface of grassy openings within barrens, which historically developed in association with stands of trees. These stands were open, with little wooded understory due to periodic fires. When fire is suppressed, the increase in vegetation in the understory eventually excludes Eggert's sunflower.

Although open to semi-open barrens and woodlands appear optimal for Eggert's sunflower, it also tolerates considerable disturbance and a range of light beneath these hardwood trees. The most vigorous populations are found under conditions of regular fire management with semi-mesic, semi-open conditions. Thriving populations were also found in pine plantations where the pine seedlings were planted into the existing vegetation or where the vegetation was scraped into piles prior to planting. It is likely that the plant was present at the sites prior to discing and that this treatment allowed these plants to expand and form colonies under conditions of reduced competition.

Distribution

Eggert's sunflower is presently known from an estimated 34 populations in 14 counties—in Alabama, one population in Blount County; in Kentucky, one population from Grayson and Hardin Counties, two populations from Edmonson and Barren Counties, and seven populations from Hart County; in Tennessee, one population each in Dickson, Marion, and Williamson Counties, two (and a portion of a third) in Maury County, three in Lewis County, four in Lawrence County, and six in Coffee County.

Most of the Tennessee populations (about 50%) are small, having fewer than 20 individual plants. The other populations contain several hundred stems. Most of the Tennessee populations are threatened either by roadside maintenance, weedy invaders, fire suppression, or development. The largest known population is found on federal lands, three occur entirely or partially on state lands, and the remainder are found in roadside rights-of-way or on private lands.

Populations of Eggert's sunflower in Kentucky have fewer than 15 individual plants, with four having only five or fewer plants. Only two populations occur on barrens, and half of these are threatened by weedy competitors or road maintenance. Five of the 13 Kentucky populations are found entirely or partially on federal lands (Mammoth Cave National Park), two on the Nature Conservancy's land and the remainder are found along roadside rights-of-way or on private lands.

Threats

Most of the known populations of Eggert's sunflower are threatened with destruction or adverse modification of their habitat. Over 50% of the known Eggert's sunflower sites are threatened by the encroachment of more competitive herbaceous vegetation or woody plants that produce shade and compete with this species for limited water and nutrients. Active management is required to ensure that Eggert's sunflower continues to survive at all sites.

Since most of the sites where this species survives are artificial (not true barrens) or manmade habitat for commercial, residential, or industrial development, intensive rights-of-way maintenance (e.g., herbicide use) is a significant threat to most of the known populations.

Barrens habitat, which is preferred by Eggert's sunflower, is disappearing from the south-central United States at a rapid rate. Most of this type of habitat has been converted to croplands, pasture, or has been developed as residential or industrial sites.

As its natural habitat disappears, Eggert's sunflower is now found in habitats that replicate the species' ecological requirements. These sites, having the accompanying assortment of weedy vegetation associated with disturbed areas, typically are disturbed habitats, such as roadside rights-of-way, ditches, road cuts, or mounds of soil. Colonization most likely occurs soon after a disturbance to the habitat. Eggert's sunflower can initially compete with other vegetation. However, as successional stages progress, this species is consequently reduced to vegetative growth from rhizomes and is eventually eliminated. Periodic burning, mowing, or thinning of vegetation on these sites favors the species by lessening competition. This sunflower is persisting at several sites due to the current mowing regime.

Eggert's sunflower is a Species of Special Concern in Tennessee, and it does not receive any formal protection since it is not listed as endangered under the state's Rare Plant Protection and Conservation Act. In Alabama, the species does not receive any state protection. In Kentucky, it is listed as endangered by the Kentucky Academy of Science, which does not have legal standing in the state.

An additional factor that threatens the survival of Eggert's sunflower is extended drought. Dry conditions cause higher than normal mortality of seedlings in the natural populations. If drought continues over an extended period of time, it could have an adverse effect on the survival of the species. Additionally, dwindling numbers in the populations of this species could increase the potential for inbreeding depression and other reproductive-related problems.

Herbivory can substantially affect seed production. One unidentified herbivore that commonly affects sunflowers in Kentucky weakens the tissue of the peduncle, causing the flower heads to drop, and can affect most of the heads produced in a clump. A type of grasshopper has been seen eating sunflower heads, but it is not known whether this is related to the peduncle damage.

Conservation and Recovery

Most Eggert's sunflower populations are found on privately owned or state-owned lands. However, one entire population and portions of four others are found in Mammoth Cave National Park (U. S. Park Service), and one population of Eggert's sunflower, which includes 62 occurrences, is on Arnold Engineering Development Center lands. Therefore, these populations are protected by the federal agencies that manage them. The Nature Conservancy owns one habitat and has introduced controlled burning.

Searches for new populations are being conducted to determine the species' full range. In 1997, more than 15 new occurrences were located in Kentucky, most of which are on private land or along roadsides.

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/

Asheville Field Office
U.S. Fish and Wildlife Service
160 Zillicoa Street
Asheville, North Carolina 28801
Telephone: (704) 258-3939, Ext. 229

References

Beatley, J. C. 1963. "The Sunflowers (Genus Helianthus ) in Tennessee." Journal of the Tennessee Academy of Science 38: 135-154.

Branson, B. A., et al. 1981. "Endangered, Threatened, and Rare Animals and Plants of Kentucky." Transactions of the Kentucky Academy of Science 42: 77-89.

DeSelm, H. R. 1989. "The Barrens of Tennessee." Journal of the Tennessee Academy of Science 64: 89-95.

Heiser, C. B., Jr., et al. 1969. "The North American Sunflowers." Memoirs of the Torrey Botanical Club 22 (3): 1-218.

Jones, R. L. 1991. "Status Report on Helianthus eggertii Small." Unpublished report to the Asheville Field Office, U. S. Fish and Wildlife Service, Asheville, North Carolina, 99 pp.

U. S. Fish and Wildlife Service. 22 May 1997. "Determination of Threatened Status for Helianthus eggertii (Eggert's Sunflower)." Federal Register 62 (99): 27973-27978.

U. S. Fish and Wildlife Service. March 1998. "Recovery Plan for Eggert's Sunflower (Helianthus eggertii )." U. S. Fish and Wildlife Service, Atlanta, 40 pp.

Warren, M. L., et al. "Endangered, Threatened, and Rare Plants and Animals of Kentucky." Transactions of the Kentucky Academy of Science 47: 84-97.