Decurrent False Aster

Boltonia decurrens

Description

Decurrent false aster, Boltonia decurrens, is a perennial plant that reaches 59 in (1.5 m) in height. Leaves are linear, very narrow, 2-6 in (5-15 cm) long, and point downward along the stem. The term decurrent refers to downward orientation of the leaves. Flowers about the size of a United States quarter-dollar coin occur in a branched, leafy inflorescence of several daisy-like heads with bright yellow disks. Flower rays are purple or violet and occasionally almost pure white. Plants bloom from July to October.

Habitat

The false aster prefers a flood plain habitat, known as prairie wetlands. It grows where damp, often marshy alluvial soils are deposited along streams and rivers, and particularly where soils have been disturbed by farming and then left untilled for several seasons. The plant community consists mostly of hardy perennial and annual grasses that are adapted to moist conditions. Flooding plays a role in maintaining the habitat that is not yet clearly understood. Floodwaters may scour away encroaching plants, reducing the false aster's competition. Silting has increased during the last hundred years and may have contributed to the plant's decline by smothering seeds and seedlings.

Distribution

Prairie wetlands habitat occurs along a 250-mi (400-km) stretch of Illinois River flood plain from LaSalle, Illinois, downstream to St. Louis, Missouri, on the Mississippi River. Several historic populations along this stretch of river have been lost to the plow or to forest succession, while others have declined for unknown reasons.

The plant still is found throughout much of its historic range but in fewer and more isolated populations. Extensive surveys conducted in 1980 and 1981, supplemented by an aerial search in 1984, located 12 populations of decurrent false aster in five Illinois counties (Morgan, Schuyler, Fulton, Marshall, and St. Clair) and two populations in one Missouri county (St. Charles).

By 1990, when the U. S. Fish and Wildlife Service (FWS) published the Decurrent Aster Recovery Plan, the species was already on the upswing, with 18 populations in Illinois and two in Missouri, although not all of these were considered self-sustaining. Staff from the Mark Twain National Wildlife Refuge in Illinois discovered hundreds of seedlings on a site at the confluence of the Missouri and Mississippi Rivers affected by the 1993 flood. The same population also was almost destroyed in 1994 during borrow operations for construction of a new levee. In a joint effort of the FWS, Army Corps of Engineers, and Missouri Department of Conservation to restore the site, seeds from local plants were broadcast around the borrow site in the fall of 1994. In the spring of 1995, flooding produced an hundreds of seedlings (perhaps spurred on by the previous year's seeding program), and researchers predicted that the following fall, Missouri would see one of the largest populations of the threatened plant ever recorded in the state—perhaps even hundreds of thousands at one location in St. Charles County.

Threats

Excessive silting may prove to be the cause of this false aster's overall decline. During the last century, highly intensive agriculture throughout Illinois and in the Mississippi River basin has increased the volume of topsoil runoff, which is then deposited in low-lying areas of the river flood plains. While intensive cultivation coupled with herbicide use eventually eradicates stands of the plant, botanists believe that some farming may actually benefit the false aster because of disturbance to the soil. Nine populations on private property are all associated with some form of low-intensity agriculture.

Conservation and Recovery

The Illinois Department of Conservation began an annual population monitoring program for Illinois in 1984. A similar program was begun in Missouri by the Missouri Department of Conservation in 1987.

Some incidents of population destruction have ultimately led to better conservation efforts. For instance, in 1986, the decurrent false aster was discovered in a borrow pit which was excavated for fill material for the access road to the Melvin Price Locks and Dam construction site in St. Charles County, Missouri. When the pool was raised behind the new locks and dam structure the borrow pit was filled with water, destroying the newly discovered population. But in an effort to mitigate this loss, a number of plants were successfully transplanted by the Missouri Department of Conservation to other Corps of Engineers lands. Subsequently, the St. Louis District Corps of Engineers successfully transplanted additional plants to a second site on Corps land. As a first step to recover this species, the FWS developed and implemented protection plans for the publicly owned areas, as outlined in the 1990 recovery plan for the species. The plan, which has as its goal delisting of the species, called for a variety of actions to achieve this end, including the survey of suitable habitat for additional populations, the protection of existing and established populations, the establishment of new populations, and the monitoring of natural and established populations. Research into the species biology, and public education through the use of brochures and displays, was also recommended. These efforts have been so successful that the species may soon be delisted, as hoped for in the plan (which had a target date of 1997.)

The plan notes that delisting may be considered when 12 geographically distinct, self-sustaining natural or established populations are protected through purchase, by easement, or by cooperative management agreements with landowners. Twelve populations were considered adequate by the Recovery Team because a number of existing populations occur in federal or state refuges or management areas and are currently active or actively managed.

Contact

U.S. Fish and Wildlife Service
Regional Office of Endangered Species
Federal Building
Ft. Snelling
Twin Cities, Minnesota 55111
http://midwest.fws.gov/

References

Ambrose, D. 1986. "Rare Flowers Such as These." Outdoor Highlights, Illinois Department of Conservation 14 (8):6-9.

Harrison, William F. 1988. "Determination of Threatened Status for Boltonia decurrens (Decurrent False Aster)." Federal Register Vol. 53, No. 219. pp. 45858-45861.

Schwegman, J. E., and R. W. Nyboer. 1986. "The Taxonomic and Population Status of Boltonia decurrens." Castanea 50 (2):112-115.

U.S. Fish and Wildlife Service. 1990. "Decurrent False Aster Recovery Plan." U.S. Fish and Wildlife Service, Twin Cities, Minnesota.