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.

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.

Cypripedium candidum is a plant of wet, rich prairies and calcareous fens. It apparently has a distinct preference for alkaline soils.

May 5 to June 10.

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.

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