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Isotria medeoloides (Pursh) Raf.
Small Whorled Pogonia
Federal Protection: Listed Threatened
State Protection: Threatened
Global Rank: G2G3
State Rank: S2
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): Yes
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: Highest Conservation Concern
Element Occurrences (EOs) in Georgia: 27
Habitat Summary for element in Georgia: Mixed hardwood- pine forests with open understory; history of nearby heavy logging, homesite or road clearing activity
Perennial herb with a waxy, hairless, pale green, almost succulent stem 1.5 - 10 inches (4 - 25 cm) tall, topped by a whorl of 4 - 6 leaves. Leaves are 0.6 - 3.3 inches (1.7 - 8.5 cm) long and 0.3 - 1.6 inches (0.8 - 4 cm) wide, pointed, waxy, bluish-green. Usually one, sometimes two flowers are held on short stalks rising from the center of the leaf whorl. Flowers have 3 green sepals (1 erect, 2 spreading) that are 0.5 -1 inch (1.2 - 2.5 cm) long; 2 round-tipped, yellow-green petals that curve forward over the center of the flower, and a down-pointing, 3-lobed lip petal with dark green veins and a yellow-green crest. The fruit is an erect capsule up to 1 inch (2.8 cm) long, held on a stalk that has elongated to 0.2 - 0.7 inch (0.5 - 1.7 cm) long.
Large Whorled Pogonia (Isotria verticillata) has dark green leaves with purple veins, a greenish-purple stem, flower stalks up to 2 inches (5 cm) long, purplish-brown sepals, and a purple-streaked lip.
Indian Cucumber-root (Medeola virginiana) has 6 or more whorled leaves, and a thin, wiry stem covered with cobwebby hairs; its lily-like flower is tiny, nodding, and pale yellow. It sometimes occurs with Small Whorled Pogonia.
More than 30 species of orchids are rare in Georgia. On this web site, see: many-flowered grass-pink (Calopogon multiflorus), pink lady’s-slipper (Cypripedium acaule), Kentucky lady’s-slipper (Cypripedium kentuckiense), yellow lady’s-slipper (Cypripedium parviflorum), green-fly Orchid (Epidendrum conopseum), Michaux's spider orchid (Habenaria quinqueseta), Appalachian twayblade (Listera smallii), Florida adder's-mouth orchid (Malaxis spicata), southern white fringed-orchid (Platanthera blephariglottis), Chapman's fringed-orchid (Platanthera chapmanii), large purple fringed-orchid (Platanthera grandiflora), monkeyface orchid (Platanthera integrilabia), purple fringeless orchid (Platanthera peramoena), crestless plume orchid (Pteroglossaspis ecristata), downy slender ladies-tresses (Spiranthes brevilabris), Florida ladies-tresses (Spiranthes floridana), Great Plains ladies-tresses (Spiranthes magnicamporum), three birds orchid (Triphora trianthophora).
Canopy gaps or openings in hardwood or mixed hardwood-pine forests on lower slopes and stream terraces with acidic soils, often with Chestnut Oak, Red Maple, Hemlock, White Pine or Virginia Pine, Lowbush Blueberry, Indian Cucumber Root, and New York Fern.
In the southeastern U.S., Small Whorled Pogonia emerges from winter dormancy in April, flowering later that month and throughout May. Non-flowering plants emerge somewhat later. Larger plants flower more frequently than smaller plants. Small Whorled Pogonia is self-pollinated and lacks the flower characteristics, such as fragrance, pollination guides, and nectar, that attract insects. A given plant may stay in flower 4 - 14 days. Shortly after pollination, the fruit begins to develop, reaching maturity in late summer and splitting open in the fall.
Seeds are dust-like and are primarily dispersed by wind and gravity. Seed production is considered low to moderate compared to other orchids. Small Whorled Pogonia seeds, like those of other orchids, lack endosperm and must develop a mycorrhizal relationship with a fungus in order to germinate and develop into a mature plant. Small Whorled Pogonia plants are known to lie dormant for as many as four years but viability is reduced in these plants once they emerge from dormancy. Small Whorled Pogonia is not known to reproduce vegetatively.
Genetic studies found that northern populations of Isotria medeoloides were more genetically diverse than southern populations. Georgia's populations were found to be genetically depauperate and quite distinct from each other, a condition typical of species with small, isolated populations. It is also typical of populations that occur on the trailing edge of a species that retreated south during glacial periods and have persisted in spite of warmer post-glacial conditions. As the climate warms rapidly in the coming decades, it is likely that Isotria medeoloides will move upslope to cooler habitats and become even rarer in the south.
Surveys are best conducted during flowering (May) and fruiting (June–August). Plants often wither soon after flowering.
Georgia, South Carolina, Tennessee, and 18 other states north to Maine and Ontario and northwest to Missouri.
Conversion of habitat to pine plantations and residential and commercial developments, logging or other mechanical clearing, overbrowsing by deer, digging by feral hogs, invasion by exotic pest plants. Decreasing genetic diversity. Increased warming due to climate change.
| Threat 1 | Threat 2 | Threat 3 | |
|---|---|---|---|
| General Threat | Transportation & service corridors | Biological resource use | Human intrusions & disturbance |
| Specific Threat | None | None | None |
Isotria medeoloides is ranked S2 by the Georgia Department of Natural Resources, indicating that it is imperiled in Georgia. It is listed as Threatened by the State of Georgia and the U.S. Fish and Wildlife Service. Twenty-six populations have been documented in Georgia, most in the Chattahoochee National Forest. Many of the populations are small and declining.
Avoid logging, trampling, and mechanical clearing. Hand clearing of small patches may benefit Small Whorled Pogonia by reducing competition from woody plants. Control deer and hog populations and eradicate exotic pest plants such as Japanese Honeysuckle. Augment populations to increase genetic diversity. Move plants to higher elevations. Address climate change.
Georgia’s plants are the southernmost populations of this species. Plants occurring at the periphery of a species’ range are thought to be of special conservation importance. Peripheral populations are usually smaller and less genetically diverse within the population, but genetically divergent from centrally located populations. These genetic differences may confer special survival traits that plants in other portions of the species’ range lack, such as the ability to survive changes in the climate or the arrival of a new pathogen. Peripheral populations may be in the process of evolving into a new species. They are especially deserving of conservation action.
Brown, P.M. and S.N. Folsom. 2004. Wild orchids of the southeastern United States, north of peninsular Florida. University Press of Florida, Gainesville.
Brumback, W.E., S. Cairns, M. Sperduto and C.W. Fyler. 2011. Response of an Isotria medeoloides population to canopy thinning. Northeastern Naturalist 18(2): 185-196. https://bioone.org/journals/Northeastern-Naturalist/volume-18/issue-2/045.018.0205/Response-of-an-Isotria-medeoloides-Population-to-Canopy-Thinning/10.1656/045.018.0205.full
Chafin, L.G. 2007. Field guide to the rare plants of Georgia. State Botanical Garden of Georgia and University of Georgia Press, Athens.
GADNR. 2020. Element occurrence records for Isotria medeoloides. Georgia Department of Natural Resources, Wildlife Resources Division, Social Circle, Georgia.
Horn, D., T. Cathcart, T.E. Hemmerly, and D. Duhl. 2005. Wildflowers of Tennessee, the Ohio Valley, and the southern Appalachians. Lone Pine Publishing, Auburn, Washington.
Massey, J.R., D.K.S. Otte, T.A. Atkinson, and R.D. Whetstone. 1983. Atlas and illustrated guide to the threatened and endangered vascular plants of the mountains of North Carolina and Virginia, Technical Report SE-20. Department of Agriculture, Southeastern Forest Experiment Station, Asheville, North Carolina. https://www.fs.usda.gov/treesearch/pubs/684
Mehrhoff, L.A. 1989. The dynamics of declining populations of an endangered orchid, Isotria medeoloides. Ecology 70(3): 783-786. https://www.jstor.org/stable/1940229
Mehrhoff, L.A. 1983. Pollination in the genus Isotria (Orchidaceae). American Journal of Botany 70 (10): 1444-1453. https://bsapubs.onlinelibrary.wiley.com/doi/abs/10.1002/j.1537-2197.1983.tb10847.x
Mehrhoff, L.A. and M.A. Homoya. 2003. Flora of North America, Vol. 26. Oxford University Press, New York. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242101723
NatureServe. 2019. Isotria medeoloides comprehensive report. NatureServe Explorer. Arlington, Virginia. http://explorer.natureserve.org/servlet/NatureServe?searchName=Isotria+medeoloides
Patrick, T.S., J.R. Allison, and G.A. Krakow. 1995. Protected plants of Georgia. Georgia Department of Natural Resources, Natural Heritage Program, Social Circle.
Stone, J.L., P.A. Crystal, E.E. Devlin, R.H.L. Downer, and D.S. Cameron. 2012. Highest genetic diversity at the northern range limit of the rare orchid Isotria medeoloides. Heredity 109: 215-221. https://www.nature.com/articles/hdy201231
USFWS. 2020. Small Whorled Pogonia (Isotria medeoloides) species accounts and related documents. U.S. Fish and Wildlife Service, Washington D.C. https://ecos.fws.gov/ecp0/profile/speciesProfile?sId=1890
Weakley, A.S. 2015. Flora of the southern and mid-Atlantic States. University of North Carolina Herbarium, University of North Carolina, Chapel Hill. http://www.herbarium.unc.edu/flora.htm
Linda G. Chafin
L. Chafin, Apr. 2007: original account
K. Owers, Feb. 2010: added pictures
L. Chafin, Mar. 2020: updated original account
