December 18, 2012

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Eastern Prairie Fringed Orchid (Platanthera leucophaea) - Threatened

Eastern Prairie Fringed Orchid. Credit Mike Redmer, USFWS

IN BRIEF: Habitat: Occurs in Maine in a single calcareous fen (Crystal Bog) Known occurrences in Maine: one occurrence in Crystal, Aroostook County, Maine Threats: Habitat loss, global warming

Additional Information

• USFWS ECOS Species Profile (recovery plan, five year reviews)
• USFWS Gulf of Maine Habitat model
• Maine Natural Areas Program fact sheet
• Center for Plant Conservation
• Canada Species at Risk Registry
• Ontario Recovery Strategy

Overview

The Eastern prairie fringed orchid is federally listed as threatened.

Species Description and Life History

One of 200 orchid species in North America, this member of genus Platanthera is identified by white,  uniformly-colored, three-parted and conspicuously fringed labellum (lowermost petal).  It can be distinguished from the closely related P. lacera by examination of the spur and lateral petals. P. leucophaea has a 2-4 cm spur and toothed lateral petals. P. lacera has a 1.4-2.1 cm long spur and entire lateral petals. This plant is 8 to 40 inches tall and has an upright leafy stem with a flower cluster called an inflorescence. The 3 to 8 inch lance-shaped leaves sheath the stem. Each plant has one single flower spike composed of 5 to 40 creamy white flowers.

This orchid is a perennial herb that grows from an underground tuber. Flowering begins from late June to early July, and lasts for 7 to 10 days. Blossoms often rise just above the height of the surrounding grasses and sedges. The more exposed flower clusters are more likely to be visited by the hawkmoth pollinators.  Seed capsules mature over the growing season and are dispersed by the wind from late August through September.  Plants may only flower once every few years. This is one of Maine’s rarest plants, and fewer than 20 plants are found each year. 

Throughout its range, the Eastern prairie fringed orchid occurs in a wide variety of habitats, from mesic prairie to wetlands such as sedge meadows, marsh edges, even bogs. It requires full sun for optimum growth and flowering and a grassy habitat with little or no woody encroachment. A symbiotic relationship between the seed and soil fungi, called mycorrhizae, is necessary for seedlings to become established. This fungi helps the seeds assimilate nutrients in the soil.

Habitat

Its habitat in Maine is the expansive Crystal Bog, actually a sphagnum-dominated fen fringed by white cedar and tamarack.  Neighboring plants are sedges, bog birch, shrubby cinquefoil, bog laurel, sheep laurel and other sphagnum bog plants.

Threats

Threats in Maine include altered hydrology of the bog, invasive plant species, succession to woody vegetation, and foot traffic. 

Distribution

Maine’s single occurrence is in Crystal, Maine. The next closest populations are in Virginia and Michigan.  Populations in New York, Pennsylvania, and New Jersey are believed to be extirpated.  Because of its small, inconspicuous nature, it may yet be discovered elsewhere in Maine and the Northeast.