South Dakota Field Office
Mountain-Prairie Region
Western Prairie Fringed Orchid
Platanthera praeclara

 

 

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picture of western prairie fringed orchidFAMILY:  Orchidaceae

DESCRIPTION: The western prairie fringed orchid is a terrestrial perennial orchid of the tall grass prairie and associated wet meadows.  At its tallest, it reaches from three to four feet high.  Approximately 2-5 thick elongate and hairless leaves hug the stem.  When flowering, an individual plant has from 5-25 white to creamy white fringed flowers.  Each of the 2.5 cm wide flowers that comprise the species' elongated inflorescence (elongated cluster of flowers) have a fringed 3-part lower petal, giving each flower a feathery appearance.

STATUS: The western prairie fringed orchid was declared as a threatened species throughout its entire range in the United States in September of 1989 (54 Federal Register 39863).  Currently a recovery plan exists with a goal of delisting.  there is no habitat conservation plan for the species.  although the state of South Dakota has a native plant protection law, it lists no specific plants.  The specie sis listed as endangered in Canada.

REASONS FOR CURRENT STATUS:  Conversion of tallgrass prairie to cropland has been the main reason for its threatened status.  Agricultural landuse conversion has created a fragmented landscape.  This geographical separation of tallgrass prairie patches reduces or eliminated the probability of pollination by moths or the movement of wind or water dispersed seed to suitable habitat.  Habitat fragmentation often reduces a species capabilities for genetic exchange and therefore the diversity necessary for a healthy population.

Exotic species provide another challenge to orchid survival.  Species such as leafy spurge, Kentucky bluegrass, and Canada thistle are competitively superior and can displace this native orchid.  Drift from chemical applications associated with exotic species control and agricultural production is lethal to the orchid and the moth species needed for pollination.

As a member of the tall grass prairie community, the orchid is a shade intolerant species, requiring ample amounts of sunlight.  Woody encroachment of trees into remaining grasslands is detrimental to this prairie species.

REPRODUCTION AND DEVELOPMENT: Western prairie fringed orchids begin to emerge in late May.  Plants flower from mid-June in the southern portion of their range to late-July in the more northerly portions.  Plants will display flowers for three weeks with individual flowers lasting for approximately 10 days.  Recruitment is accomplished primarily through sexual reproduction.  Plants require nocturnal fertilization provided by a specific group of moths adapted to harvesting nectar from the long spur (sac-like appendage) of the orchid.

While harvesting this nectar, the widely spaced anthers (pollen bearing structure) of the orchid deposit pollen on the moth's eyes.  Plant reproduction occurs when moths with pollen laden eyes visit another orchid.  Once fertilization occurs, seeds are mainly wind dispersed.  Some dispersal also occurs through water.  A mycorrhizal fungus within the soil is required for seedling establishment and continued plant development.  Despite its dependence on moths for fertilization, moths are not restricted to western prairie fringed orchid nectar.  Depending on geographic location, soil moisture and other factors, and individual orchid can survive from 2-6 years.

RANGE: Western prairie fringed orchids were historically found in the tallgrass prairie regions west of the Mississippi River in Oklahoma, Missouri, Kansas, Iowa, Nebraska, Minnesota, and North and South Dakota, and Manitoba, Canada.  The eastern prairie fringed orchid (P. leucophaea) is a similar species whose range encompasses regions east and west of the Mississippi.  Although the range of this eastern orchid overlaps with that of the western orchid, there are no known cases of their coexistence.

POPULATION LEVEL: Less than 40% of the original rangewide population of western prairie fringed orchid remains.  The largest orchid population (approximately 2,000 plants as of 1996) is located in the Sheyenne National Grasslands in North Dakota.  In addition to this North Dakota population, two other populations exist; one in southeastern Manitoba and the third in northwest Minnesota.  These three northern populations serve as the stronghold for the species.  Smaller population complexes (500-1,000 plants within a 5-6 sq mile area) exist in Nebraska and Minnesota; additional smaller isolates also exist in Iowa.

HABITAT:  Moist tallgrass prairie and sedge meadows are appropriate habitat for the western prairie fringed orchid.  Big and little bluestem, switchgrass, Indiangrass, and northern reedgrass are common associates in orchid habitat.

MANAGEMENT AND PROTECTION:   Proper management for western prairie fringed orchid includes preservation and maintenance of native tall grass prairie habitat.  This includes habitat acquisition and conservation easements for preservation, establishment of appropriate management plans and compliance with existing and future protective regulations.

Little information exists on the influence of habitat management practices on orchids.  Repeatable, rangewide research is required to determine the effects that burning, haying, and grazing have on orchid populations.  These land management practices may affect the species depending on their timing, frequency and intensity.  Best management programs should be initiated and/or maintained on lands supporting and adjacent to orchid populations.

Complementary to management and research actions, public education and participation encouraging conservation of the orchid, and tallgrass prairie habitat are essential to the recovery of the species.  If you suspect western prairie fringed orchids were or are in your area, please contact the US Fish and Wildlife Service.

Information summarized from:

http://mountain-prairie.fws.gov/feature/orchid.html

http://northdakotafieldoffice.fws.gov/endspecies/species/western_prairie_fringed_orchid.htm

US Fish & Wildlife Service.  1996.  Platanthera praeclara (western prairie fringed orchid) recovery plan  (10.56 MB). USFWS, Ft. Snelling, Minnesota.  vi + 101 pp.

USFWS Western Prairie Fringed Orchid Species Profile page

 

Last updated: September 9, 2013

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