Navasota Ladies'-tresses

Spiranthes parksii

Description

Navasota ladies'-tresses, Spiranthes parksii, is considered one of the rarest and least-studied orchids of North America. This perennial, terrestrial orchid has parallel-veined, grasslike leaves that grow mostly from the base of the plant. Leaves are usually absent when flowers are present. Stems attain a height of about 12 in (30 cm). A solitary spike of small white flowers with green mid-veins is arranged as a spiral along a slender stalk. Floral bracts are tipped with white. The bottom lip of the flower is distinctly ragged. Plants bud in early October, flower from October to mid-November, and bear fruit from mid-October to late November. Roots are a cluster of tubers.

Habitat

This species is associated with the post-oak savannah community of east-central Texas. The habitat is lightly wooded and extends along the banks of lesser tributaries within the Navasota and Brazos river drainages. This orchid is a constituent of later successional stages of these mature woodlands. It prefers clearings within the woods that are naturally maintained by characteristics of the soil or by limited grazing.

Distribution

Navasota ladies'-tresses were first collected along the Navasota River in Brazos County in 1945. Subsequent efforts to relocate the plant during the 1950s were unsuccessful, and it was thought extinct until rediscovered near College Station (Brazos County) in 1976. Although not well-studied, the plant is probably endemic to east-central Texas.

Currently, about 30 populations of Navasota ladies'-tresses are known from the six-county area around the cities of Bryan and College Station (Brazos, Burleson, Grimes, Madison, Robertson, and Washington Counties). An isolated population comprised of six sterile and one flowering plant was discovered in 1987 in the Angelina National Forest near the Louisiana border in Jasper County. The total number of plants throughout the range was estimated at 5,500 in 1984.

Threats

The explosive growth of Texas A & M University and associated urban development at Bryan and College Station over the last decade have encroached significantly on orchid habitat in Brazos County. Exploration for oil and lignite in the area has also disturbed several population sites. The late twentieth century discovery of a vigorous Grimes County population provides some buffer against extinction should development overrun the major population centers in Brazos County.

Although there has been little evidence of collecting so far, this species could easily be targeted by orchid collectors because of its rarity. Wild plants typically do not survive transplantation, however. Commercial cultivation techniques have not yet been developed.

Conservation and Recovery

Botanists from Texas A & M University are studying and monitoring orchid populations. Recovery efforts will concentrate on establishing at least two self-sustaining populations that are safe from disturbance. Because all known populations are on private land, this recovery effort will be attempted through purchase of land or easements, and by negotiation of conservation agreements with landowners.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P.O. Box 1306
Albuquerque, New Mexico 87103-1306
Telephone: (505) 248-6911
Fax: (505) 248-6915
http://southwest.fws.gov/

References

Catling, P. M., and K. L. McIntosh. 1979. "Rediscovery of Spiranthes parksii Correll." Sida 8 (2): 188-193.

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

U. S. Fish and Wildlife Service. 1987. "Endangered and Threatened Species of Texas and Oklahoma (with 1988 Addendum)." U. S. Fish and Wildlife Service, Albuquerque.

U. S. Fish and Wildlife Service. 1984. "Navasota Ladies'-Tresses (Spiranthes parksii ) Recovery Plan." U. S. Fish and Wildlife Service, Albuquerque.