Fairy slipper orchid  (Calypso bulbosa)

The fairy slipper orchid is listed on Appendix II of CITES (3).

The fairy slipper orchid, which has been called the most beautiful terrestrial orchid in North America (4), bears a single, showy flower on a single, dainty, purple stem (4) (5) (6). The petals and sepals of each intricate and colourful flower are held above a large, highly-modified petal (called the lip) like a crown (2) (7). The lip is a slipper-shaped pouch, hence this plant’s common name (2). The flowers, which emit a distinct, pleasant, vanilla-like aroma (4) (5), range in colour from rich purple, through shades of pink to white and are lightly veined (2) (4), while the lip is white to purple with purplish spots, and the inside of the pouch is lined with purple to reddish veins (2) (4). The area near the throat of the pouch is decorated with three ridges, bearing white or yellow hairs (2) (4).

Each plant has a single, dark green, oval leaf measuring up to 3.5 centimetres long (2) (6). Both the single leaf and flower stem rise from a shallow corm, with few, short and slender roots (2) (4). On blooming plants it is sometimes possible to see the top of the corm (4). The species name bulbosa refers to the bulb-like nature of the corms (2), while Caplypso comes from the name of the sea nymph in Homer’s Odyssey (5). Four varieties of the fairy slipper orchid are recognised, each differing slightly in their appearance (2).

The fairy slipper orchid has a circumpolar distribution, occurring in Europe, Asia and North America (5). In Europe is does not grow south of 57 ºN (5), and in North America is occurs from Alaska to Labrador, south to northern California, Arizona, Michigan and Maine (6). Calypso bulbosa var. bulbosa occurs in Europe and Asia, Calypso bulbosa var. speciosa is found in Japan, while Calypso bulbosa var. Americana and Calypso bulbosa var. occidentalis both occur in North America (2)

The fairy slipper orchid occurs in forests and woodlands (6), generally in shady areas (4) (5), where it grows in humus (4) (7), or in the decaying vegetation covering the forest floor (2) (4). It may also grow in sphagnum bogs (5), moss, or on top of rotting logs and tree stumps (4).

In autumn, generally around September, the single, dark green leaf of the fairy slipper orchid sprouts from the corm (2) (4) (7). This leaf lasts through winter, even surviving under snow in the cold parts of its range (2) (4). With the arrival of spring, the orchid flowers. In Europe, this may be as soon as the snow melts (5), while in parts of North America it is said to occur in May and June (2) (7), and the flower is able to withstand any late frosts that may occur. Shortly after the flower blooms, the leaf fades for the summer (4).

The flower of the fairy slipper orchid possesses no nectar and instead attracts its pollinators by deception (5). The scent and shape of the flower mimics those that do have nectar, which lures bumble bees (Bombus species) to the bloom (5). The bees land on the lip of the flower and enter the pouch in search of food. Failing to find any, the bee exits the pouch, rubbing against the column overhanging the pouch opening as it does so. Pollen is deposited on the bee and is then transferred to the next flower it visits (4).

Following pollination, the fairy slipper orchid flower fades rapidly (2). By late summer, the capsule has ripened and the seeds are dispersed. The leaf withers and the plant becomes dormant until September, when a new leaf will be produced and the cycle will commence again (7).

Habitat destruction is a threat for the fairy slipper orchid in California, where logging for the timber industry is the primary cause (4). Logging and development also threatens the fairy slipper orchid throughout other parts of its range (2). Another significant threat to this stunning plant is the presence of people, either accidentally causing damage when they come to view and photograph these beautiful flowers, or, more seriously, when collectors deliberately remove the plants from the wild for cultivation in gardens (2) (4). In addition, the shallow growth of the fairy slipper orchid makes it susceptible to predation by feral pigs. In some areas, pigs have been known to destroy entire colonies (4).

The fairy slipper orchid is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that any international trade in this species should be carefully monitored (2). Hopefully this may lessen the threat of over-collection. In addition, this species is protected within many parks and reserves throughout its range (4) (8).

For further information on the conservation of orchids see:

• Orchid Conservation International:
  www.orchidconservation.org