Cypripedioideae (lady's slipper orchids)

Characteristics and anatomy

Flowers of Cypripedioideae typically present a prominent pouch and a showy dorsal sepal and petals; many species have attractive patterns or bright colors. Unlike most orchids, members of this subfamily possess two fertile stamens rather than a single fused one. The pouch functions as a temporary trap: an insect seeking nectar or refuge slips in, then must climb out by a narrow route that brings it into contact with the reproductive parts. Pollen is usually carried in compact masses (pollinia) that attach to the insect and are moved from flower to flower during subsequent visits. For more on the floral parts, see stamens and for pollination mechanics consult pollen transfer.

Genera and distribution

The subfamily contains several well-recognized genera, including Cypripedium, Paphiopedilum, Phragmipedium, Selenipedium and the recently recognized Mexipedium. Their native ranges vary: Cypripedium occurs across temperate regions of the Northern Hemisphere, Paphiopedilum is mostly Asian and often epiphytic or lithophytic, Phragmipedium is native to the Americas, and Selenipedium grows in Central and South America. Habitats range from woodland floors to limestone outcrops and tropical forest branches.

Pollination and ecology

Lady's slipper orchids use a trap-and-release pollination method. Insects, commonly bees or flies, enter the pouch and are guided past the flower's pollen and stigma as they exit. This increases the chance that pollinia adhere to the insect and are later deposited on another flower. Some species have evolved color patterns, scent cues or nectar guides that specifically attract particular pollinators.

History, taxonomy and uses

Historically the group has sometimes been treated as a separate family (Cypripediaceae) because of its distinctive morphology, but it is now most commonly placed as a subfamily of Orchidaceae. Lady's slippers are prized in horticulture for their unusual blooms; Paphiopedilum in particular forms a significant part of the ornamental orchid trade and many species are cultivated by enthusiasts and in botanical collections.

Conservation and notable facts

Many species face threats from habitat loss, collection in the wild and environmental change. Because of their rarity and high demand, parts of this group are protected under international trade regulations and national laws. Cultivation, habitat protection, and propagation programs are important tools for conserving these charismatic and biologically interesting orchids.