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Orchidaceae: Cypripedium acaule Ait.
(pink lady's-slipper, moccasin flower )

Pink lady's-slipper bears a single flower on a stem 15-30 cm tall. There are two large leaves at the base of the stem but otherwise the flowering stalk is leafless. Plants without flowers have no above-ground stem. (Acaule means without stem.) The leaves of the pink lady's-slipper are oblong elliptic, green above with a shiny, silvery undersurface. A single flower is subtended by a green, leafy bract. Flower colour ranges from pale pink to purple with darker purplish lines.adada flowersWhite forms are relatively common.1 The slipper pouch (lip) is folded in on itself forming a narrow channel-like opening. The inner surface of the pouch bears many fine dark hairs and the entire flower is finely pubescent (hairy). Pepals and sepals are lanceolate, brown green in colour and slightly twisted. Pink lady's slipper blooms June to late summer in Nova Scotia, elsewhere May to late June depending on location and habitat. Only a small proportion of flowering plants produce fruits, apparently because the species is a "deceptive orchid". Such orchids offer no rewards to pollinators, hence pollinators do not seek out their flowers and pollination is poor.2 Pink lady's-slipper is found on wet, moist or dry sites with acid soil and at least some shade3; sites can include coniferous and mixed forest, swamps and bogs. Munden 1 comments that "most people think of it as a woodland deweller but the most prolific sites are in the open among Rhodora, Blueberry and Bracken". Cypripedium acaule has a widespread distribution from Alberta east to Newfoundland and PEI and south to Alabama and Georgia.
Sources | Notes & Refs | Selected Web Resources | Line Drawing

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June 20, 2007. Halifax County: Bluff Trail. Photographer: Ocotillo.
Cypripedium acaule, Pink Lady's-slipper Cypripedium acaule, Pink Lady's-slipper

August 4, 2008. Shelburne County: Indian Field. Photographer: JackPine.
Cypripedium acaule

Two flowering stalks with fruits.

Cypripedium acaule

Plant with old flowering stalk but no fruit.

Cypripedium acaule Cypripedium acaulet


Cypripedium acaule

Habitat: white pine/red oak woods


Selected Web Resources

Notes & References

  1. Munden, C. 1999. Native orchids of Nova Scotia. A field guide. University College of Cape Breton Press
  2. O'Connell, L.M. & Johnston, M.O. 1998. Male and female pollination success in a deceptive orchid, a selection study. Ecology 79(4): 1246-1260. (The study was conducted in Halifax Co.)
  3. Reddoch, J.M. & Reddoch, A.H. 1997. The orchids in the Ottawa district: floristics, phytogeography, population studies and historical review. The Canadian Field-Naturalist 111(1), 1-185.