Minnesota is the home of approximately 42 orchid species, including six in the genus Cypripedium - acaule, arietinum, calceolus var. parviflorum (small yellow lady's-slipper), calceolus var. pubescens (large yellow lady's-slipper), candidum, and reginae. Smith, Welby R. (1993). Orchids of Minnesota. Minneapolis: University of Minnesota Press, provides a comprehensive and readable guide to the species and their locations. He reports that the two calceolus varieties (one illustrated above) differ primarily in the size of the bloom with sepals and petals of the var. parviflorum dark red instead of yellowish green, and that both generally are to be found in "coniferous/Sphagnum swamps, meadows, fens, moist prairies, and occasionally upland coniferous or hardwood forests....both shade and direct sunlight, in peat and mineral soil." He also reports that var. parviflorum seems to bloom approximately a week earlier than var. pubescens.
The opening image of this website shows a small section of a fairly large colony of terrestrial slipper orchids that four members of the Orchid Society off Minnesota (http://www.orchidsocietyofminnesota.com/) have been observing over the past three years. The colony appears to be comprised of Cyp. parviflorum var. pubescens, Cyp. parviflorum var. parviflorum, and natural hybrids between the two. "Our" colony, consistent with Smith's observations, flowers in late May and into late June. Temperatures and moisture probably have some effect on the blooming date from year to year.
This year (2005), the deer - the White-Tailed Odocoileus virginianus - got to the colony before we did. Green plants are "favorites" in the spring and it was obvious that they had dined on many young slipper plants.
The image just above - Trillium grandiflorum - was taken in close proximity to "our" colony. Its presence is no guarantee that Cyp. parviflorum will be found nearby, but when it's seen the probability of finding Cyp. parviflorum increases. We've asked friends with habitat appropriate for Cyp. parviflorum to be on the lookout for Trillium next spring so that we check for additional colonies of slippers.
(March 2006)