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.