|Lady slipper orchid|
|An orchid of the genus Paphiopedilum|
Lady's slipper orchids (also known as lady slipper orchids or slipper orchids) are orchids in the subfamily Cypripedioideae, which includes the genera Cypripedium, Mexipedium, Paphiopedilum, Phragmipedium and Selenipedium. They are characterised by the slipper-shaped pouches (modified labellums) of the flowers – the pouch traps insects so they are forced to climb up past the staminode, behind which they collect or deposit pollinia, thus fertilizing the flower. Unlike other orchids, Cypripedioideae have two fertile anthers — they are "diandrous".
The subfamily Cypripedioideae is monophyletic and consists of five genera.
The Cypripedium genus is found across much of North America, as well as in parts of Europe and Asia. The state flower of Minnesota is the Showy Lady's Slipper (Cypripedium reginae). The Lady's Slipper is also the official provincial flower of the Canadian province of Prince Edward Island.
Paphiopedilums are found in the tropical forests of southeast Asia reaching as far north as southern China. Paphiopedilum is quite easy to cultivate and therefore is popular among orchid enthusiasts. In fact, overcollecting of this genus has been so extensive that many species are now sub-viable in their natural habitats.
Pink Lady's Slipper, found in Bristol, Vermont (Cypripedium acaule)
Spotted Lady's Slipper (Cypripedium guttatum) in Alaska Peninsula National Wildlife Refuge
Pink Lady Slippers, found in Rhode Island (Cypripedium acaule)
Further reading 
- Cox, A.V., A. M. Pridgeon, V. A. Albert, and M. W. Chase. 1997. Phylogenetics of the slipper orchids (Cypripedioideae: Orchidaceae): nuclear rDNA ITS sequences. Plant Systematics and Evolution 208: 197-223. PDF Abstract
- Pridgeon, A.M.; Cribb, P.J.; Chase, M.W. & F. N. Rasmussen (1999): Genera Orchidacearum Vol. 1, Oxford U. Press. ISBN 0-19-850513-2