Cypripedium candidum Muhlenberg ex Willdenow
Small white lady's-slipper
The specific epithet candidum is the Latin meaning "shining
white," in reference to the labellum of this species.
DESCRIPTION: Plant
small, arising from a rhizome with a fascicle of numerous fibrous roots,
10-40 cm high; typically many stems may arise from the same rootstock. Leaves
2-5, ovate, deeply plicate, 5-15 cm long and 2-6 cm wide; densely pubescent.
Leaves typically held nearly erect and sheathing the stem. Flower
1 or rarely 2, subtended by an elliptical, green foliaceous bract 3-11 cm
long by 1-3 cm wide. Sepals apparently two (the result of the fusion
of the two lateral sepals behind the labellum), greenish-yellow and lightly
streaked madder-purple; dorsal sepal ovate to elliptical, 1.5-2.5 cm long
and 0.5-1.5 cm wide; lateral sepals united and similar to dorsal sepal,
with tip usually split. Petals colored as sepals, lance-linear, 2-4
cm long and 3-8 mm wide. Labellum pouch-shaped, inflated, egg-shaped,
1.7-3.3 cm long, opening above with inrolled edges; white and shiny or waxy
in appearance, streaked with purple inside.
SIMILAR SPECIES: Cypripedium candidum could perhaps be confused
with C. calceolus var. pubescens or
C. calceolus var. parviflorum;
however, both of these varieties of C. calceolus are yellow-flowered,
never white-flowered.
HABITAT: Cypripedium candidum is a plant of wet, rich prairies
and calcareous fens. It apparently has a distinct preference for alkaline
soils.
FLOWERING DATES: May 5 to June 10.
POLLINATION: The flowers are very fragrant, which likely serves to attract
pollinators. Catling and Knerer (1980)
studied the pollination of C. candidum in Ontario, where they found
it to be pollinated by adrenid and halictid bees.
WI DISTRIBUTION: 
U.S. DISTRIBUTION:
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