CPC Plant Profile: Small Whorled Pogonia
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Plant Profile

Small Whorled Pogonia (Isotria medeoloides)

Photo Credit: New England Wildflower Society
Description
  • Global Rank: N/A
  • Legal Status: N/A
  • Family: Orchidaceae
  • State: MI, MO, NC, NH, NJ, NY, OH, PA, RI, SC, TN, VA, VT, WV, CT, DC, DE, GA, IL, MA, MD, ME, ON
  • Nature Serve ID: 137976
  • Date Inducted in National Collection: 02/21/2003

Isotria medeoloides is a small, perennial orchid of deciduous forests with a grayish-green, smooth stems that bears at its summit a whorl of light-green, pointed leaves and yellow-green flowers. This distinctive leaf whorl gives the plant its name. Only one other co-occurring orchid, its close relative Isotria verticillata, looks similar but has a purplish stem and the stem bearing the ovary is longer than the ovary. Often cited as "the rarest orchid east of the Mississippi," this orchid is critically imperiled in 14 (78%) of the 18 states and provinces in its native range. Nowhere is it considered secure or common (Vitt 1997).

Participating Institutions
Updates
Center for Plant Conservation
  • 12/03/2021

This species occurs on upland sites in mixed deciduous or mixed deciduous/coniferous forests that are generally in second- or third-growth successional stages. Characteristics common to most sites are sparse to moderate ground cover, relatively open understory canopy, and mostly highly acidic soil. Light availability may be a limiting factor. No direct correlation with other plant species has been identified. The plant species remains rare in spire of thousands of acres of suitable habitat. There is a poorly understood relationship between this orchid species and mycorrhisal fungus. The threats to this species are habitat destruction, collection and grazing.

  • 10/14/2020
  • Demographic Research

Dr. Pati Vitt (Chicago Botanic Garden, pvitt@chicagobotanic.org) conducted part of her graduate research on the demography of Isotria medeoloides.

  • 10/14/2020
  • Seed Collection

In October of 2003, seed was collected from the population located at East Alton, NH.

Elvia Ryan
  • 08/13/2018

The orchid Isotria medeoloides (small whorled pogonia) is primarily located in the lakes region of New Hampshire and Maine.  Basically, healthy Isotria medeoloides plants will flower in early June and begin to form seed pods in August.  The seed pods are dehiscing with minute seeds that are essentially an embryo in an envelope with little food reserves.  It is extremely difficult to study this plant because it will be remain dormant for 8 to 10 years at a time.  An initial study by the New England Wild Flower Society (NEWF) was conducted to track how the act of canopy cutting affected the number of emerging stems over a five year period.  It was observed that the plants flourished and are still increasing in this particular location where canopy thinning was conducted.  This data is important because it indicates that this form of management of allowing more light sometimes does work therefore facilitating conservation management of these populations.  In October of 2003, seed was collected from the population located at East Alton, NH.  Seed was then placed in plankton netting (utilizing the Rasmussen & Whigham technique) inside film slide mounts and buried under an inch or two of leaf litter.  Slides were attached by fishing line to two different stakes located within the Isotria population so that they could be more easily located.  On June 8, 2007, slides #14 and #4 were removed.  Results of both slides looked great.  Even though #14 had almost three times as many seeds as #4, the results were almost identical.  The seeds had been tested with triphenyltetrazolium chloride (TTC) which measures metabolic action in the seeds.  Even the seeds that failed to pick up the stain appeared to have healthy looking embryos.  On June 20th, seeds were scored for viability:  slide #4 scored 58.9% stained viable (116/197) and slide #14 scored 57.3% stained viable (369/644).  On June 7, 2017, slides Q-372-1 and Q-372-2 were collected.  Results of the 2017 Study:  Q372-1 seeds appear healthy (87%), stain viable (42%);  Q372-2 seeds appear healthy (96%), stain viable (45%).  Q372--1 had about 13% dead embryos which what not seen in the other seed packet.  TTC staining is probably an underestimation of viability.  How these seeds can possibly sustain themselves with almost no food reserves after being buried for over 13 years is undetermined.  To date, no one has been able to germinate a seed of Isotria medeoloides in the lab even when using the associated fungus.  Conclusions are as follows:  (1) Isotria medeoloides has the potential to form a long-lived seedbank in the wild.  (2)  A seedbank could explain why new plants (or what appear to be new plants) emerge over many years.  (3) In-situ seedbank tests could help better understand the potential for conservation of terrestrial orchid populations.  (Brumback et al. 2018)

Nature Serve Biotics
  • 05/02/2017

A widely distributed species with approximately 201 element occurrences with better than poor viability known. The largest cluster of sites is centered around the Appalachian Mountains of New England and coastal Massachusetts, with two moderate-sized clusters centered around (1) the southern Appalachians and (2) the Coastal Plain and Piedmont of Virginia, Delaware, and New Jersey. There are also a few widely scattered outlying sites. Populations are typically very small and the total number of individuals is estimated to be less than 3,000. Only historic sites are known in New York, Maryland, and Missouri, and the species is believed to have been extirpated in Vermont and the District of Columbia. Most extant sites considered viable are now protected, with site-specific protection and monitoring efforts well underway. However, without voluntary landowner protection, many I. medeoloides populations could be lost to housing development and non-selective logging.

  • 01/01/2010

Conversion of woodland habitat for housing, industrial, or highway development (von Oettingen 1992) is identified as the primary factor in loss of populations Overcollection for horticultural or research purposes has been cited as a secondary threat (v

  • 01/01/2010

Approximately 201 populations known (NatureServe 2017), centered on the eastern seaboard with outlying populations in Ontario and Michigan. While no estimates are available on the total number of plants in North America, based on average population size, it is likely to total under 5,000 plants.

  • 01/01/2010

The New England Wild Flower Society (Framingham, Massachusetts) has monitored the responses of Isotria medeoloides to experimental canopy thinning at one New Hampshire site since 1997. Likewise, plants have been followed at the site since the early 1980's (Brumback and Fyler 1988, Brumback 2003). Dr. Lawrence Zettler (Department of Biology, Illinois College, 1101 West College Avenue, Jacksonville, Illinois 62650, USA), a research associate at the Marie Selby Botanical Gardens in Florida, is studying mycorrhizal interactions in Isotria medeoloides. Dr. Pati Vitt (Chicago Botanic Garden, pvitt@chicagobotanic.org) conducted part of her graduate research on the demography of Isotria medeoloides. Dr. Dennis Whigham, Dr. Melissa McCormick, and Jay O'Neill  of the Smithsonian Experimental Research Center have been studying this plant and its fungal associates in the mid-Atlantic states.

  • 01/01/2010

The New England Wild Flower Society, in cooperation with the U. S. Fish and Wildlife Service, is conducting experimental canopy thinning and long-term population monitoring at a site in East Alton, New Hampshire, with considerable success (see above). The U. S. Marine Corps hosts one of North America's largest populations of Isotria medeoloides on their Quantico Base in Virginia. They plan military exercises and timbering operations in collaboration with the U. S. Fish and Wildlife Service so as not to threaten the population, and Base Natural Resource specialists monitor the plants annually (U. S. Marine Corps 2001).

  • 01/01/2010

Identify mycorrhizal associates and their impacts on seed germination, seedling establishment, habitat needs, and viability of populations Understand patterns of dormancy, specifically environmental factors causing plants to enter and recover from dormancy and means to predict which stems will enter dormancy Study seedbanking and seed viability in the field Determine patterns of genetic relatedness among colonies, populations, and the primary population centers and outlier sites for the orchid across its range Develop consistent methods for monitoring populations quantitatively across the species' range From existing long-term demographic data and new studies of marked plants, develop a population viability analysis and predict minimum viable population size for the orchid so that protection strategies can target the most vital and healthy populations Conduct systematic surveys for the orchid using refined habitat models Determine the impacts of herbivores on plant survivorship and reproduction Characterize collateral impacts of research visits on plant vigor and reproduction Implement habitat management such as moderate canopy thinning where succession appears to be inhibiting plant growth and reproduction.

  • 01/01/2010

Develop techniques for propagation of Isotria medeoloides, both to reduce collecting pressures on existing wild populations and to provide stock for population augmentation if needed (note: one transplantation effort to date has been largely unsuccessful [Brumback and Fyler 1996]).

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Nomenclature
Taxon Isotria medeoloides
Authority (Pursh) Raf.
Family Orchidaceae
CPC Number 2350
ITIS 43614
USDA ISME2
Common Names Small Whorled Pogonia | Lesser Five Leaves | Little Five Leaves | Green Fiveleaf Orchid | Lesser whorled Pogonia
Associated Scientific Names Isotria medeoloides | Arethusa medeoloides | Isotria affinis | Odonectis affinis
Distribution Isotria medeoloides is found along the Appalachian belt from Ontario through New England, south to Tennessee, Georgia, and South Carolina, and west to Michigan (NatureServe 2003).
State Rank
State State Rank
Connecticut S1
District of Columbia SX
Delaware S1
Georgia S2
Illinois S1
Massachusetts S1
Maryland SH
Maine S2
Michigan S1
Missouri SH
North Carolina S1S2
New Hampshire S2
New Jersey S1
New York S1
Ohio S1
Ontario S1
Pennsylvania S1
Rhode Island S1
South Carolina S2
Tennessee S1
Virginia S2
Vermont SX
West Virginia S1
Habitat

Isotria medeoloides inhabits semi-open, mesic forests of eastern North America. Mehrhoff (1988) describes these as mixed deciduous forests in second- or third-growth successional stages. Soils in sites with the orchid are highly acidic, and many are fragipans on shallow-to-bedrock (or shallow-to-clay) slopes of 8-22% where lateral water drainage from upslope sources occurs (NatureServe 2001), particularly in the northeastern part of its range. Occasionally, the orchid can be found in more calcium-rich sites, including limestone areas in New York, Missouri, and Ontario, where a more species-rich assemblage of herbaceous plants are associated with the orchid. In Georgia, the species is described from partially shaded gaps in mixed hardwood-conifer forests with an open understory and sparse herbaceous layer. Some sites have historically supported agriculture, and forest stands overlying Isotria medeoloides vary from 30 to over 75 years in age (von Oettingen 1992). The orchid is frequently found where leaf litter and decaying wood abound. Braided channels of vernal streams are promising places to search (Van Alstine et al. 1996). Recently, specific habitat models for the plant have been constructed using geographic information systems that combine features such as elevation, soil type, forest composition, and light availability, helping to better predict where the orchid might occur. Such a model by Casabona and Giles (2001) correctly predicted the majority of known locations for the orchid in Prince William Forest Park, Virginia. Sperduto and Congalton (1996) and the U. S. Fish and Wildlife Service (2001) have also refined the habitat "search image" for I. medeoloides, contributing to more precisely targeted searches. For example, nine new populations of I. medeoloides found in Maine and New Hampshire using Sperduto and Congalton's model. Evidence from field studies suggests that Isotria medeoloides responds favorably to increased light levels and that reproduction may be suppressed by a closing canopy (Mehrhoff 1980, 1988, Brackley 1991). Management to thin the canopy over subpopulations of the orchid in New Hampshire has stimulated flowering, reduced the proportion of plants entering dormancy, and has fostered a higher density of stems (New England Wild Flower Society 1998, Brumback 2003).

Ecological Relationships

Isotria medeoloides plants may live for several years, remaining dormant for several years at a time (Mehrhoff 1989, Vitt 1991). Plants that remain dormant more than three years have a small probability of re-emerging (Vitt 1991). With few specialized structures or scents to attract insect pollinators, plants appear to be primarily self-pollinating (Mehrhoff 1983). Seed production is characterized as low to moderate, with 9,600 seeds produced by one plant (Mehrhoff 1983), but reproduction is generally efficient due to the orchid's capacity for self-fertilization (Vitt and Campbell 1997). Although multiple stems can arise from a single rootstock, Isotria medeoloides does not reproduce vegetatively (Mehrhoff 1983). Taller plants with a larger whorl diameter tend to flower more frequently than smaller plants (Mehrhoff 1989), and may emerge somewhat earlier in the year (Brumback and Fyler 1988). Plants emerge in May at the northern edge of the orchid's range, and in April farther south. Flowers can be maintained from several days to two weeks (Homoya 1977, Mehrhoff 1983). The fruit capsule matures in the fall. Dust-like orchid seeds often disperse by wind from the parent plant, but precise dispersal mechanisms are undescribed for this species.

There, associated species include Chestnut oak (Quercus prinus), tuliptree (Liriodendron tulipifera), white or Virginia pine (Pinus strobus or P. virginiana) that predominate in the canopy, blueberry species, New York fern (Thelypteris novaboracensis), the look-alike Medeola virginiana, ferns, club mosses, low-lying evergreen forbs such as partridgeberry (Mitchella repens), a shrub layer of witch hazel (Hamamelis virginiana), and frequently a canopy of paper birch (Betula papyrifera) (NatureServe 2001, (Patrick et al. 1995).
 

Recent research has found that the abundance of Russulaceae, both in the soil and on nearby ECM root tips, was significantly related to orchid prior emergence. Both abundance and prior emergence history were predictive of future emergence (Rock-Blake et al 2017). 

Pollinators
Common Name Name in Text Association Type Source InteractionID
Other
Self Only Not Specified Link
Self Only Not Specified Link

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