Cypripedium calceolus (L.) var. pubescens (Willd.) Correll

Large yellow lady's-slipper

The specific epithet calceolus is the Latin meaning "little shoe," in reference to the slipper-like shape of the labellum. The varietal name pubescens is the Latin meaning "downy" or "hairy," in reference to the hairy nature of the plant.

DESCRIPTION: Plant arising from a rhizome with a fascicle of numerous fibrous roots, 15-80 cm high; several to many stems may arise from the same rhizome. Leaves 3-5 (-6), ovate to ovate-lanceolate, plicate, 5-20 cm long and 4-10 cm wide; pubescent. Flowers 1-2, each subtended by a ovate to ovate-lanceolate, green foliaceous bract 4-10 cm long by 1-4 cm wide. Sepals apparently two (the result of the fusion of the two lateral sepals behind the labellum), green streaked with brown to brown (but highly variable in coloration); dorsal sepal ovate, 3-7 cm long and 1-3.5 cm wide; lateral sepals united and similar to dorsal sepal but typically spirally twisted, tip typically divided. Petals colored as sepals, linear-lanceolate, 4-9.5 cm long and typically less than 1 cm wide; petals usually spirally twisted. Labellum pouch-shaped, inflated, obovate, 1.5-6 cm long, opening above with inrolled edges; yellow streaked or spotted inside with madder-purple.

Cypripedium calceolus var. pubescens would most likely be confused with C. calceolus var. parviflorum. C. calceolus var. parviflorum is distinguished primarily by the smaller labellum and darker sepals.

In the southern part of Wisconsin, this variety is typically found growing in moist, rich deciduous woods. Further north it occurs in similar habitat but may also occur in boggy or swampy areas (where it also occasionally found in the south). The plant is rarely found in clayey soils, and shows a distinct preference for areas of limestone. In Door County, where this taxon is particularly numerous, it often grows in limestone gravel along roadsides.

May 10-July 15.

According to Stoutamire (1967), plants are pollinated by a number of different species of small bees, primarily adrenid and halictid bees. The plants are also visited and sometimes pollinated by a variety of Diptera.

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