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Cypripedium acaule Ait.
Pink LadyslipperFederal Protection: No US federal protection
State Protection: Unusal
Global Rank: G5
State Rank: S4
Element Locations Tracked in Biotics: Yes
SWAP High Priority Species (SGCN): No
Element Occurrences (EOs) in Georgia: 211
Habitat Summary for element in Georgia: Upland oak-hickory-pine forests; piney woods
Perennial herb with two large basal leaves and a single flower stalk topped with a showy pink flower. Leaves are 3.5 - 12 inches (9 - 30) long and 1 - 6 inches (2.5 - 15 cm) wide, green and hairy on the upper surface, gray on the lower surface, with bluntly pointed tips and raised, parallel veins. The flower stalk is up to 2 feet (61 cm) tall. The flower is up to 2.6 inches (6.7 cm) long, with a showy, pink (rarely white), pouch- or slipper-shaped lip petal and two narrow, twisted, reddish-brown or green outwardly spreading petals. A large, green sepal curves over the top of the flower. Fruit is an oval capsule, about 1.4 inches (3 - 4 cm) long, filled with thousands of dustlike seeds.
In flower, Pink Lady’s Slipper resembles no other Georgia plant. Non-flowering plants may be recognized by the large pair of leaves (single in juvenile plants), rising directly from the ground without an aboveground stem; the leaves have conspicuously raised, parallel veins and are covered with sticky hairs. Lily-leaved Tway-blade (Liparis liliifolia) and Showy Orchis (Galearis spectabilis) also have paired leaves at ground level; their leaves are smooth, glossy, and somewhat succulent with a prominent midvein but without the conspicuous parallel veins. Speckled Wood-lily (Clintonia umbellulata) also has broad basal leaves; it occurs in similar habitats. Its leaves are usually more than 2 in number, and are hairless and glossy, with a deeply channeled midvein and no other conspicuous veins.
Yellow Lady’s Slipper (Cypripedium parviflorum) is state-listed as Rare. It occurs in Georgia's Blue Ridge counties in rich, moist cove forests. For more information, see: http://explorer.natureserve.org/servlet/NatureServe?searchName=Cypripedium%20parviflorum
Kentucky Lady’s Slipper (Cypripedium kentuckiense) is state-listed as Endangered. It occurs in two counties in Georgia's upper Coastal Plain on seepy forested slopes with a mixed hardwood canopy. For more information, see: https://georgiabiodiversity.org/natels/profile?es_id=21658
Upland pine and mixed pine-hardwood forests with acidic soils; in the mountains, it often occurs near edges of Rhododendron thickets and mountain bogs.
Pink Lady’s Slipper flowers are pollinated by bees that are attracted to their color and fragrance. A bee enters the colorful, inflated lip through a one-way opening and quickly discovers that there is neither pollen nor nectar available, and that it cannot readily escape. The bee can exit the flower only through two openings at the back of the lip. As it leaves from one of these openings, its back brushes against the female part of the flower, depositing a packet of pollen from the last PLS flower that it visited, and picking up a new packet of pollen from the male part of the flower. The packet is taken to the next visited flower; the pollen is held in small packets that stick to the bee’s back where it is not accessible to the bee and can’t be scraped off by the bee's legs. Bees soon learn to avoid these flowers because they fail to provide nectar or pollen; as a result, few flowers are pollinated.
Although flowers remain on the plants for several weeks to increase the chances of pollination, fewer than 10% of plants in a population will produce fruit in a given year. Fortunately, each fruit contains thousands of seeds. But the seeds are tiny, containing no stored food reserves, and must land on a patch of soil containing a specific fungus that provides nutrients for germination and subsequent plant growth. Pink Lady’s Slipper plants dug from the wild and transplanted into gardens rarely reproduce due to the lack of this fungus. They also fail to thrive and will die after a couple of years, unless the specific fungus is present at the transplant site.
Surveys are best conducted during flowering (April–June); they go dormant soon after fruiting (May–July).
Throughout eastern North America, the upper Midwest, and adjacent Canadian provinces.
Logging, clearing, or development of upland forests, poaching, and exotic invasive species, especially Japanese honeysuckle.
Pink Lady’s Slipper is relatively abundant and has been observed in almost all north Georgia counties, although many of these populations, especially in the metro Atlanta area, have been destroyed. Large numbers of plants are known on national forest land. It is state-listed primarily because of the threat posed by poachers, who dig the plants for their gardens or for commercial sale. Plants dug from the wild and transplanted into gardens rarely survive for very long.
Periodically apply prescribed fire; occasional fire in upland forests will maintain the pine-dominated forests and patchy hardwood canopy that favor Pink Lady’s Slipper. Prosecute plant poachers. Protect known sites from clearcutting and development. Eradicate exotic pest plants such as Japanese honeysuckle. Never buy plants of this species without determining that it came from an ethical source.
Argue, C.L. 2011. The pollination biology of North American orchids, vol. 1. Springer Science + Business Media, New York. https://www.google.com/books/edition/The_Pollination_Biology_of_North_America/xG-1gb9rf9kC?hl=en&gbpv=1&dq=inauthor:%22Charles+L.+Argue%22&printsec=frontcover
Brown, P.M. and S.N. Folsom. 2004. Wild orchids of the southeastern United States, north of peninsular Florida. University Press of Florida, Gainesville.
Chu, C. and K.W. Mudge. 1996. Propagation and conservation of native lady’s slipper orchids (Cypripedium acaule, C. calceolus, and C. reginae), pp. 107-112, In C. Allen (ed.), North American Native Terrestrial Orchids: Propagation and Production, Conference Proceedings, Germantown, Maryland.
Cullina, W. 2007. Pollinating Cypripedium acaule (Pink Lady-slipper). https://www.yumpu.com/en/document/read/15742504/pollinating-cypripedium-acaule-pink-lady-slipper-william-cullina
Davis, R. W. 1986. The pollination biology of Cypripedium acaule (Orchidaceae). Rhodora 88: 445-450. https://www.jstor.org/stable/23314206
GADNR. 2020. Element occurrence records for Cypripedium acaule. Georgia Department of Natural Resources, Wildlife Resources Division, Social Circle, Georgia.
Gill, D.E. 1996. The natural population ecology of temperate terrestrials: what pink lady's-slippers, Cypripedium acaule, tell us. In C. Allen (ed.), North American Native Terrestrial Orchids: Propagation and Production, Conference Proceedings, Germantown, Maryland.
NatureServe. 2019. Cypripedium acaule comprehensive report. NatureServe Explorer. Arlington, Virginia. http://explorer.natureserve.org/servlet/NatureServe?searchName=Cypripedium%20acaule
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.
Primack, R. and E. Stacy. 1998. Cost of reproduction in the pink lady's slipper orchid (Cypripedium acaule, Orchidaceae): an eleven-year experimental study of three populations. American Journal of Botany 85(12): 1672-1679. https://bsapubs.onlinelibrary.wiley.com/doi/full/10.2307/2446500
Sheviak, C.J. 2003. Species account for Cypripedium acaule. Flora of North America, Vol. 26. Oxford University Press, New York. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242101544
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, April 2007: original account
K. Owers, Jan. 2010: updated status and ranks, added pictures
Z. Abouhamdan, April 2016: removed broken link
L. Chafin, Feb 2020: updated original account.
