Cypripedium acaule Aiton

This species is accepted, and its native range is Central & E. Canada to N. Central & E. U.S.A.


Flowering in April to June.


Widespread in North America, most abundandy in the eastern and northeastern parts of its range. Canada (Newfoundland, Nova Scotia, New Brunswick, Prince Edward Island, Quebec, Ontario west to Saskatchewan and Alberta), U.S.A. (Ne,v England south to South Carolina, Georgia, Tennessee and Alabama and west to Minnesota, Ohio, Indiana, Kentucky).


In a variety of habitats from wet sphagnum bog to dry Pinus (pine) forest, usually in moderate shade where the soil is rich in humus, strongly acidic and thoroughly aerated. Flowering in April to June.

General Description

A terrestrial herb 20-45 cm tall, with a very short erect underground stem, 1-7 cm long, covered by two to three glabrous tubular sheaths and growing from a short underground rhizome. Leaves nvo, plicate, basal, spreading-suberect, elliptic, 10-28 cm long, 5-15 cm wide, glandular-pubescent, ciliate, glossy bright green. Inflorescence one- or rarely two-flowered; peduncle erect, to 40 cm long, glandular-pubescent; bract arching over flower, foliaceous, lanceolate, acuminate, 4-5 cm long, 1-1.5 cm wide, glandular- pubescent. Flower large, nutant, with yellow-green to maroon sepals and petals and a pink or rarely white lip, the staminode green to pink; pedicel and ovary 1-1.5 cm long, glandular-pubescent. Dorsal sepal often arching over lip, ovate- to elliptic-lanceolate, acuminate, 3-5 cm long, 0.5-1.7 cm wide, glandular-ciliate on basal margins, sparsely glandular-pubescent without and within; synsepal elliptic- to ovate-lanceolate, acute to obtuse, 3-4.5 cm long, 1-2.3 cm wide, sparsely glandular-pubescent without, glandular-ciliate. Petals deflexed at 45°, slightly twisted, slightly falcate, linear-lanceolate to lanceolate, acute, 4-6 cm long, 1-1.7 cm wide, densely pubescent at the base within. Lip ellipsoid-obovoid, longer than the sepals, 4-6 cm long, 2.5-3.5 cm wide, densely pubescent on inner surface at base, pubescent on front margin and around mouth on outer surface, lacking discernable side lobes, the orifice elongate and narrow, the margins incurved except at the apex. Column 1-1.2 cm long, pubescent on dorsal surface; staminode convex, suborbicular- rhombic to ovoid-deltoid, obtuse to 1.8 cm long and 1.4 cm wide, densely pubescent.

Native to:

Alabama, Alberta, Connecticut, Delaware, District of Columbia, Georgia, Illinois, Indiana, Kentucky, Maine, Manitoba, Maryland, Massachusetts, Michigan, Minnesota, New Brunswick, New Hampshire, New Jersey, New York, Newfoundland, North Carolina, Northwest Territorie, Nova Scotia, Ohio, Ontario, Pennsylvania, Prince Edward I., Québec, Rhode I., Saskatchewan, South Carolina, Tennessee, Vermont, Virginia, West Virginia, Wisconsin

Moccasin Flower

Cypripedium acaule Aiton appears in other Kew resources:

Date Reference Identified As Barcode Type Status Has image?
Schwarz, V.T., USA 45327.000 No
57353.000 No
5791.000 No
72742.000 No
Eaton, D.C. [s.n.], Connecticut K000363696 Yes
Eaton, D.C. [s.n.], USA K000363695 Yes
Canada K000363699 Yes
Torrey [s.n.], New Jersey Cypripedium humile K000363697 Yes
Gouldie [s.n.], Canada Cypripedium humile K000363738 Yes
Fraser [53], USA Cypripedium humile K000363698 Yes

First published in Hort. Kew. 3: 303 (1789)

Accepted by

  • Govaerts, R. (1999). World Checklist of Seed Plants 3(1, 2a & 2b): 1-1532. MIM, Deurne.
  • Govaerts, R. (2003). World Checklist of Monocotyledons Database in ACCESS: 1-71827. The Board of Trustees of the Royal Botanic Gardens, Kew.
  • Herkert, J.R. & Ebinger, J.E. (eds.) (2002). Endangered and Threatened Species of Illinois: status and distribution 1: 1-161. Endangered species protection board, Springfield, Illinois.



  • Aiton, W. Original description of Cypripedium acaule. 3, (1789).

  • Cypripedioideae:

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  • Kew Living Collection Database

    Common Names from Royal Botanic Gardens, Kew Living Collection

  • Kew Names and Taxonomic Backbone

    The International Plant Names Index and World Checklist of Selected Plant Families 2022. Published on the Internet at and
    © Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families.