Habitat Assessment and Survey for the Small Whorled Pogonia (Isotria medeoloides)

Coastal Resources, Inc. (CRI) conducted a habitat assessment and species survey for federally threatened small whorled pogonia (Isotria medeoloides) for an approximately 100-acre proposed development project at the Fort Belvoir North Area in Fairfax County, VA.  The small whorled pogonia is a small terrestrial orchid that occurs in scattered populations in the Eastern United States. In Virginia, the small whorled pogonia can be found in third growth upland forests on northerly or easterly facing slopes that range from almost level to moderately sloping. Sites supporting the species have a distinctly open understory, often found near small forest openings adjacent to a small stream, road, or fallen/dead tree. Soils associated with the species are acidic sandy loams with low to very low nutrient content. 

Despite being relatively widespread in the Eastern U.S., extant colonies consist of less than 25 individuals.  As a result, the small whorled pogonia has been listed as federally threatened under the Endangered Species Act (ESA) and state endangered in Virginia. The small whorled pogonia is known to occur at Ft. Belvoir, and the U.S. Army Corps of Engineers (USACE) requested that a survey be conducted within the Fort Belvoir North Area to addresses the ESA requirements for the proposed project. The habitat assessment and survey were conducted during the U.S. Fish and Wildlife Service (USFWS) optimal survey period for the species (i.e., June 1 – July 20). Prior to conducting the survey, CRI conducted a reconnaissance of the site to identify the limits of development and to determine suitability of habitat. Based on habitat requirements from existing literature, habitat suitability was categorized as Unsuitable, Marginal, and Suitable.

Based on the reconnaissance, CRI targeted the slopes along existing stream corridors within the proposed security fence, as these areas were relatively mature forests dominated by mixed hardwood species. The survey team surveyed parallel transects along the stream corridors, spaced about 25 feet apart.  However, areas identified as suitable were surveyed closer to maximize chances for detection.  Any species observed that had a physical similarity to the small whorled pogonia (e.g., Indian cucumber root, Medeola virginiana or common whorled pogonia, Isotria verticillata) were carefully inspected, positively identified, and noted. Although some suitable and marginal habitat was identified in the stream corridors, no small whorled pogonias were identified.  Numerous colonies of common whorled pogonia were documented within the suitable small whorled pogonia habitat along the unnamed tributary that flows southeast across the southern portion of the study area.  Outside of the stream corridors, the study area consisted of regenerating or young forest dominated by Virginia pine (Pinus virginiana) and sweet gum (Liquidambar styraciflua) and young mixed hardwood forest with a relatively dense understory consisting of ericaceous shrubs. Most of these areas were considered unsuitable and were not surveyed or were surveyed with less effort.  Following the survey, CRI produced a brief memo summarizing the findings, including methods, results, site photos, and a comprehensive list of plant species observed. 


Fort Belvoir, Fairfax County, VA


U.S. Army Corps of Engineers, Baltimore District

Key Services:

  • Habitat Assessment
  • RTE Plant Survey