Calypso is a genus of orchids containing one species, Calypso bulbosa, known as the calypso orchid, fairy slipper or Venus's slipper. It is a perennial member of the orchid family found in undisturbed northern and montane forests. It has a small pink, purple, pinkish-purple, or red flower accented with a white lip, darker purple spottings, and yellow beard. The genus Calypso takes its name from the Greek signifying concealment, as they tend to favor sheltered areas on conifer forest floors. The specific epithet, bulbosa, refers to the bulb-like corms.[3]
Calypso bulbosa is a low growing herbaceous plant with a nearly egg-shaped underground storage organ called a corm. It is encased in dead leaf sheaths and has elongated roots. Calypso orchids are typically 8 to 20cm in height.[3] Plants have a single leaf that measures 1 to 6.5centimeters long with a width of 1.2 to 5.2cm. The leaf is suborbiculate, nearly circular, or ovate, egg shaped in outline. The base of the leaf is often cordate, having an indentation like the top of a heart.[4] The leaf often has a very long petiole, a leaf stalk attaching it to the plant.[5] The leaf sprouts in the autumn and remains green over the winter. It withers a short time after flowering.[6]
Plant blooms with a purple-pink hermaphroditic, zygomorphic and threefold flower. The protruding petals and sepals are pink to purple in color, about 10 to 12 millimeters long and about 2 to 4 millimeters wide. The lip (labellum) is white to pink with pink or yellow spots. It has a wide, shoe-shaped cavity in the back and is about 15 to 25 millimeters long.[7] They do not bloom until May and June usually after snow melt.[8] A new bulb is formed by the plant each year, but bulbs from one or two years prior can remain attached and firm.[7] Plants seldom live for longer than five years.[9]
Flowers
Leaf Top
Leaf underside
White form of Calypso bulbosa var. occidentalis
Taxonomy and systematics
The chromosome count is 2n = 28. Since the orchid seed does not provide any nutrient tissue, germination only takes place when infected by a mycorrhizal root fungus.
Illustration of Calypso bulbosa as Cypripedium bulbosum by Johann Jacob Roemer in Flora Europaea inchoata (1797)
Illustration of Calypso bulbosa (as syn. Calypso borealis) in "Curtis's Botanical Magazine" vol.54 (N.S. 1) pl. 2763 (1827)
Calypso bulbosa Rchb. F. by Kränzlin, Friedrich; Müller, Walter in Abbildungen der in Deutschland und den angrenzenden gebieten vorkommenden grundformen der orchideenarten (1904)
Varieties
Four varieties and one nothovariety, a variety of hybrid origin that is established in the wild, are recognized:[2]
Image
Variety
Distribution
Calypso bulbosa var. americana(R.Br.) Luer
most of Canada, western and northern United States
Calypso bulbosa var. bulbosa
Sweden, Finland, Baltic States, much of Russia, Mongolia, Korea
Calypso bulbosa nothovar. kostiukiaeCatling
Alberta (C. bulbosa var. americana × C. bulbosa var. occidentalis)[13]
Calypso bulbosa var. occidentalis(Holz.) Cockerell
from Alaska and British Columbia south through the Cascades, Rockies, and Sierra Nevada to California
Calypso bulbosa var. speciosa(Schltr.) Makino
Japan, China (Gansu, Jilin, Nei Mongol, Sichuan, Tibet, Yunnan)[14]
Synonyms
Calypso bulbosa has 29synonyms of the species or one of its four varieties, including 16 species.[2][15][16][17][18]
The genus Calypso is named in reference to the nymph Calypso, whose name means concealment. The habitat of these plants in the deep woods habitat metaphorically hides them from plant hunters. The species name, bulbosa, means possessing a bulb, referring to its growth habit.[19]Calypso bulbosa is known by the common namesfairy slipper,[19]fairyslipper orchid,[20] and fairy-slipper orchid,[21] due to the prominent lower lip of the flower resembling a slipper.[19] Similarly it is known as Venus slipper or Venus' slipper,[22][23] but this name is also applied to orchids of the genus Cypripedium because of the mythological association with the goddess Venus.[24] It is also known as angel slipper, slipper orchid, redwoods orchid, deer-head orchid,[22] and calypso.[23]
This species' range is circumpolar, extending around the northern hemisphere.[4] In Europe this includes just Sweden, Finland, the Baltic states, and the northern parts of European Russia.[2] It includes California, the Rocky Mountain states and most of the most northerly states of the United States; most of Canada; China, Mongolia, Korea and Japan—see external links for map.[25][26] It is found in subarctic swamps and marshes as well as shady places subarctic coniferous forests.
Conservation
Although the calypso orchid's distribution is wide, it is very susceptible to disturbance. The conservation organization NatureServe evaluated the species in 2025 and found it to be secure at the global level (G5). However, in the United States they found it to be vulnerable (S3) in Arizona, Wyoming, South Dakota, Minnesota, and Maine. In two other states, Wisconsin and Michigan, they rated it as imperiled (S2). In Canada it also is rated as vulnerable in Saskatchewan and the Yukon Territory and imperiled in New Brunswick. More critically it is critically imperiled (S1) on the Island of Newfoundland and possibly locally extinct in Nunavut.[1]
In Sweden it was listed as vulnerable in the 2020 Swedish Red List.[27] Similarly, Finland evaluated it as vulnerable in the 2019 national Red Book.[28]
Ecology
At least near Banff, Alberta, the calypso orchid is pollinated by bumble bees (Bombus (Pyrobombus) and B. Psithyrus). It relies on "pollination by deception", as it attracts insects to anther-like yellow hairs at the entrance to the pouch and forked nectary-like structures at the end of the pouch but produces no nectar that would nourish them. Insects quickly learn not to revisit it. Avoiding such recognition may account for some of the small variation in the flower's appearance.[26][29]
Uses
Attempts at garden cultivation are not successful and transplanting usually will kill plants. The structure of the corms suggest that the species is dependent on mycorrhizal relationships with soil funguses that are lost during transplantation.[9] The corms have been used as a food source by North Americannative peoples. The Nlaka'pamux of British Columbia used it as a treatment for mild epilepsy.[30]
↑ Mosquin, T. (1970), "The Reproductive Biology of Calypso bulbosa (Orchidaceae)", Can. Field-Nat., 84 (3): 291–296, doi:10.5962/p.342973, S2CID267444858 Summarized by Coleman and by Boyden
Fernald, M. L.; Weatherby, C. A. (1929). "Proposed Amendments to the International Rules of Botanical Nomenclature". Rhodora. 31 (365): 91–96. JSTOR23300448.
Web sources
Naturvårdsverket Staff (24 June 2025). "Norna". Naturvårdsverket[Swedish Environmental Protection Agency] (in Swedish). Retrieved 25 September 2025.
NatureServe (5 September 2025). "Calypso bulbosa". NatureServe Explorer. Arlington, Virginia. Retrieved 25 September 2025.
Suomen Lajitietokeskus (25 September 2025). "Neidonkenkä – Calypso bulbosa"[Lady's slipper orchid – Calypso bulbosa]. Punaisen kirjan verkkopalvelu[Red List online service] (in Finnish). Retrieved 25 September 2025.
VASCAN; Acadia University; Université de Montréal Biodiversity Centre; University of Toronto Mississauga; University of British Columbia (2025). "Calypso bulbosa - Database of Vascular Plants of Canada (VASCAN)". Canadensys. Archived from the original on 5 December 2021. Retrieved 26 September 2025.
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