Eastern Prairie Fringed Orchid

Platanthera leucophaea

Description

The eastern prairie fringed orchid is a perennial which, following winter dormancy, sends up leaves and a flower spike in May. The alternate leaves are lanceolate to linear and are 4-8 in (10-20 cm) long. The upper leaves are much smaller than the lower. As many as 40 large white flowers are borne on the stem which grows to a height of 47 in (120 cm). The flowers have extremely long spurs and a deeply fringed three-part lower lip. They become fragrant after sunset and are pollinated by night-flying hawkmoths.

The eastern prairie fringed orchid forms a species pair with the closely related western prairie fringed orchid Platanthera praeclara, also listed as a Threatened species. Before P. praeclara was described, the two species were both known as P. leucophaea. The species has also been known as Habenaria leucophaea. These two orchids are distinguished by details of flower structure and their respective pollination strategies. The eastern species places its pollen on the proboscis of visiting moths; the western species has larger flowers, which deposit pollen on the moths' eyes.

Habitat

The eastern prairie fringed orchid grows in tall-grass calcareous silt loam or moist sand prairies. It is also found in open portions of calcareous wet-lands, such as fens, marshes, and bogs. The species requires full sunlight and is vulnerable to natural succession.

Distribution

This orchid once occurred throughout much of the grasslands and open wetlands of the upper Midwest and eastern United States. Its range extended from Nebraska to Maine and south to Oklahoma and possibly Arkansas. West of the Mississippi River, the species no longer occurs in Oklahoma, Arkansas, Nebraska, or Missouri. In the East it has been extirpated from New York, Pennsylvania, New Jersey, Indiana, and possibly Virginia. Overall, the species has declined about 70% according to historic county records.

The eastern prairie fringed orchid is now known from about 50 populations in seven states: Illinois, Iowa, Maine, Michigan, Ohio, Virginia, and Wisconsin. The small Virginia population, which consisted of three plants on private land in 1983, has been seen only intermittently since then. Additional populations are found in Canada (Ontario and New Brunswick). In the United States the orchid is most numerous in Michigan. Moderate populations occur in Wisconsin and Illinois.

In Michigan there are 18 populations in nine counties. A 1984 survey counted 1,322 flowering stems. Several populations numbering more than 100 plants occur on prairies that border Saginaw Bay. Three other large populations, totaling about 900 plants, are found on upland prairies along Lake Erie. These sites are owned by the state of Michigan. Southern Michigan populations are small and occur in isolated wetland habitats.

Nine small populations occur in eight counties in south and southeast Wisconsin. A single large population of several hundred plants is found in Kenosha County on a protected sand prairie bordering Lake Michigan.

In Ohio, three declining populations survive. The largest contained about 60 plants in 1987, a decline from 367 plants in 1982. Another population declined from 46 plants in 1984 to two plants in 1988. The third population is located on land frequently flooded by Lake Erie; in 1988 it contained 14 plants.

Illinois, which historically supported the largest populations of the orchid, has suffered the greatest decline. The species formerly grew in 33 counties across the upper two-thirds of the state, but now occurs in only eight populations in eight counties in the Chicago area. Two additional populations occur in cemetery prairies in eastern and western Illinois. Only two populations, located in a county bordering Lake Michigan, contain more than 100 plants.

One small population, consisting of three plants, remains in Iowa. The single Maine population, which occurs on low, swampy land, contains about 20 plants.

Threats

The decline of the eastern prairie fringed orchid has been the result of the conversion of prairie habitat to cropland. Although most conversions have already taken place, this process continues to pose a threat to surviving populations.

Perhaps the greatest continuing threat to the orchid is natural succession. Many of the largest populations occur on land that also supports successional vegetation. Without proper management orchid numbers on these sites are likely to decline. Other populations occur on small prairie remnants, which limits the possibility of population increase.

Conservation and Recovery

Although the species is not known to occur on federal land, a number of important populations are offered state protection. About half of the sites in Michigan are protected, as is the largest Wisconsin population. Most of the Illinois populations are under some form of protection.

Contacts

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

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
300 Westgate Center Dr.
Hadley, Massachusetts 01035
http://northeast.fws.gov/

References

Bowles, M. L. 1983. "The Tallgrass Prairie OrchidsPlatanthera leucophaea and Cyripedium candidum Muhl. ex Wilid.: Some Aspects of Their Status, Biology, and Ecology, and Implications Toward Management." Natural Areas Journal 3:14-37.

Case, F. W., Jr. 1987. Orchids of the Western Great Lakes Region. Cranbrook Institute of Science, Bloomfield Hills, Michigan.

Luer, C. A. 1975. Tile Native Orchids of the United States and Canada, Excluding Florida. New York Botanical Garden.

Sheviak, C. J. 1974. "An Introduction to the Ecology of the Illinois Orchidaceae." Illinois State Museum, Scientific Paper 14.

Sheviak, C. J., and M. L. Bowles. 1986. "The Prairie Fringed Orchids: a Pollinator-Isolated Species Pair" Rhodora 88:267-290.