Yellow Lady’s Slipper

Cypripedium calceolus
Orchidaceae (orchids)

A beautiful perennial orchid frequently growing in colonies. Flowers have three long, brown, twisted “flags”—the upright one being a sepal, the other two, on either side of the “slipper,” being two lateral petals. The bright yellow slipper, or lip, is a third, modified petal. The petal-like structure behind the lip is actually a pair of fused sepals. Thus there are 3 sepals and 3 petals. Blooms April–June. Leaves broad, prominently parallel-veined, clasp the stem, to 6 inches long, sharply pointed, hairy.

Similar species: Three species of lady’s slippers grow in Missouri. Showy lady’s slipper (C. reginae) has white flowers with sepals and lateral petals that don’t twist; the lip is pink- or purple-tinged. Small white lady’s slipper (C. candidum) has flowers whose purplish or brown-tinged “flags” twist; the lip is white with purplish streaks on the inside surface. It is rare and found in only one location in extreme southern Missouri.

Height: to 2 feet (var. pubescens); var. parviflorum is shorter.
Habitat and conservation: 
Grows in upper and middle elevations of wooded slopes of ravines and stream valleys, facing north or east, in acid soils in rich upland forests. We have two subspecies in our state. Small yellow lady’s slipper (var. parviflorum) has a lip ¾-1 inch long, flags reddish purple to brown, and 4-6 leaves per stem. Large yellow lady’s slipper (var. pubescens) has a lip 1-2¼ inches long, flags yellowish green with purplish streaks, and 3-4 leaves per stem.
Distribution in Missouri: 
Scattered nearly statewide; absent from the Mississippi Lowlands. The smaller variety, parviflorum, grows in western and southern counties. The hairier and taller variety, pubescens, grows in eastern Missouri.
Most orchids are declining. Habitat destruction for logging, grazing, and conversion to pasture causes much of the loss. Root diggers also damage populations, selling the roots as medicinal herbs, even though the folkloric basis for thinking it useful as a drug hardly justifies wiping out these plants. Collecting orchids for gardening is the saddest reason for their decline, since it is no secret that lady’s slippers nearly always die upon transplanting.
Human connections: 
Touching this plant can cause a skin rash in some people. Most orchids are declining, usually due to human activities. Cora Steyermark wrote, “Anyone who has any conception of the struggle an orchid must undergo to perpetuate itself would leave any member of this family in its natural habitat.”
Ecosystem connections: 
Orchids are a pinnacle of the coevolution between flowers and pollinators. To acquire nectar, insects (mostly bees) must follow a labyrinthine obstacle course through the flower, providing the necessary cross-pollination in the process. Then, the seeds require a symbiotic fungus to survive.
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