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Published In: Species Plantarum 2: 951. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native


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1. Cypripedium calceolus L. (yellow lady’s slipper)

Pl. 112 c–e; Map 460

Flowering stems 15–80 cm long, usually densely hairy, with 1 or 2 flowers. Leaves 3–6 per flowering stem, 14–20 cm long, more than 4 cm wide, ovate to elliptic, hairy. Sepals 2–5 cm long, ovate‑lanceolate, undulate or somewhat spirally twisted, yellowish green or reddish purple to brown. Lateral petals 3–9 cm long, longer than the lip, linear‑lanceolate, spirally twisted, yellowish green or reddish purple to brown. Lip 2–5 cm long, obovoid, the margins rolled inward along the edge of the opening, yellow (rarely white), usually with red spots on the inside surface and around the opening. Column 15–25 mm long, the staminode triangular, yellow with red spots. 2n=20. April–June.

Scattered nearly throughout Missouri, except for the Mississippi Lowlands (U.S., Canada, Europe, Asia). North‑ and east‑facing slopes of ravines and stream valleys in rich, mesic, upland forests.

Typical C. calceolus occurs in Europe and Asia. The status of the North American populations is still much debated by orchidologists, with some arguing that the complex is too variable to allow taxonomic recognition of morphotypes differing in flower color and size, as well as the shape and degree of twisting of various components of the perianth. Others argue for recognition of 4 or more species in the complex. The classification followed here treats the large‑flowered and small‑flowered lady’s slippers as varieties of a single species. Users of the flora will have difficulty in determining occasional plants to variety, as is evident from the overlapping values for the characters used in the key below.

A third member of the complex probably is distinct enough to be considered a separate species, C. kentuckiense C.F. Reed (Atwood, 1984, 1985). It is characterized by a pale, lemon‑yellow or rarely white, very large lip having a larger opening than is typical of C. calceolus. This taxon occurs sporadically from Louisiana to Oklahoma, with a few of the northwestern Arkansas populations documented from counties adjacent to the Missouri border. It should be sought in southwestern Missouri, in marshy, rich soil along permanent streams.

Cypripedium calceolus is often dug from the wild by gardeners, and many populations have grown smaller over time. The rootstocks of yellow lady’s slipper also are still collected commercially in Missouri for sale in the medicinal plant trade. They are used by herbalists primarily as sedatives and antispasmodics.


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1 1. Lip smaller, 2–3 cm long; sepals and lateral petals reddish purple to brown (except in albino forms, where yellowish green); leaves usually 4–6 per flowering stem...1A. VAR. PARVIFLORUM

Cypripedium calceolus var. parviflorum
2 1. Lip larger, 3–6 cm long; sepals and lateral petals yellowish green with reddish purple streaks; leaves usually 3 or 4 per flowering stem...1B. VAR. PUBESCENS Cypripedium calceolus var. pubescens


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