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Wisconsin Plant of the Week

Platanthera leucophaea (Nutt.) Lindl.

Orchidaceae

Common Name:

eastern prairie white-fringed orchid

07/13/2002

Eastern prairie white-fringed orchid is one of Wisconsinís most beautiful native perennials. It grows on a smooth stout stem up to 1 m tall with a spike of up to 40 flowers that bloom in early July.

Like all orchids the flowers have 3 sepals and 3 petals -- 2 lateral petals and a middle petal, called the lip or labellum, thatís larger and has a different shape. These flowers are creamy white with a deeply 3-parted lower lip. The center lobe of the lip is deeply notched and each lobe is fringed at least to the middle. Leaves are alternate, lance-shaped and clasp the stem, getting smaller from the base to the flowers.

Plants regenerate vegetatively during the growing season from a long tuber by forming a new primary tuber and a bud that develops into the root system and shoot for the following year.  If the tuber is damaged two plants may form, but otherwise multiple tubers are rare. Since vegetative reproduction is so uncommon the species depends on the long-term survival of adults and seed reproduction. 

Western prairie white-fringed orchid (P. praeclara) is very similar but confined to the tall grass prairies west of the Mississippi. Our eastern species, with a floral structure that allows pollination by a wider variety of pollinators, has adapted to a wider range of habitats. It prefers full sun in wet prairies, sedge meadows, lake shore ridge and swale complexes, and on the floating mats of open bogs and fens.

Both prairie fringed orchids are characteristic of moth-pollinated flowers -- white flowers with no nectar guides, very long nectar-containing spurs and a sweet nocturnal fragrance.

  • Origin of the name: Platanthera, flat anthers, from platanus, L. flat or broad; leucophaea, off-white, from leuco, L. white and phaeo, dark or dim
  • Range:  Eastern N. Amer., s. to VA, MO
  • WI Range:  southern third, n. to Sheboygan, Sauk counties
  • Common associates:  big bluestem, mountain mint in wet prairies; wiregrass sedge marsh fern, white cedar
  • Wetland Indicator Status: FACW+
  • Coefficient of Conservatism: 10, WI; 10, Michigan, 10, Chicago Region
  • Federal Threatened Species, State Endangered in WI, MN, IL, MI
  • More info: Key to WI Orchids, WI Threatened and Endangered Species
  • Ref: C.J. Sheviak and M.L. Bowles. 1986.  Rhodora 88:267-290.
     

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