Regularity: Regularly occurring
Regularity: Regularly occurring
Global Range: Extant in seventeen states and two Canadian provinces. Manitoba south to central Nebraska, Iowa; east to Alabama, Kentucky, Maryland, New York and Ontario. Also in North Dakota, South Dakota, Minnesota, Wisconsin, Michigan, Connecticut, New Jersey, Ohio, Indiana, Illinois. Extirpated from Pennsylvania and possibly Saskatchewan.
Comments: Mesic blacksoil prairie, wet blacksoil prairie, glacial till hill prairie, sedge meadow, calcareous fen, glade. Calcareous soils. In Manitoba, this species can be found in moist calcareous (calcium-rich, or alkaline) prairie areas or openings in wooded grasslands. It most often grows in relatively undisturbed grassland, but can also be found in moderately disturbed sites such as roadside ditches.
Flower-Visiting Insects of White Lady's Slipper in Illinois
(the showy, but deceptive, flower of this orchid provides neither nectar nor pollen to insect visitors; the most effective pollinators are small bees with pollinia attached to their bodies; one observation is from Stoutamire, otherwise observations are from Catling & Knerer)
Anthophoridae (Nomadini): Nomada sp. exp np (CK)
Halictidae (Halictinae): Augochlorella striata exp (CK), Halictus confusus exp (CK), Lasioglossum atlanticus exp (CK), Lasioglossum pilosus pilosus exp (CK), Lasioglossum rohweri exp (CK); Halictidae (Sphecodini): Sphecodes sp. exp np (CK); Andrenidae (Andreninae): Andrena barbilabris exp (Stm), Andrena ziziae exp (CK)
Chalcididae: Unidentified sp. exp (CK)
Elateridae: Unidentified sp. exp np (CK)
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 81 to >300
Comments: Minnesota: Over a hundred occurrences. The number of occurrences has declined 52% from historic county records (Natural Areas J. 3(4):19).
Life History and Behavior
Persistence: PERENNIAL, Long-lived
Molecular Biology and Genetics
Barcode data: Cypripedium candidum
Statistics of barcoding coverage: Cypripedium candidum
Public Records: 1
Specimens with Barcodes: 3
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: N2 - Imperiled
Rounded National Status Rank: N4 - Apparently Secure
NatureServe Conservation Status
Rounded Global Status Rank: G4 - Apparently Secure
Reasons: Although Cypripedium candidum's range has decreased rapidly in the last century, there are still numerous extant occurrences. Also, the protected occurrences extend across its range, thus potentially maintaining some degree of genetic diversity.
Global Short Term Trend: Relatively stable (=10% change)
Comments: Encroachment by woody plants and successional change, habitat destruction, collection by wildflower hunters, herbicide application, loss of pollinators.
Biological Research Needs: Gene exchange in variously-sized populations; genetic relationships between populations throughout range; pollinator behavior with respect to C. candidum; germination and growth requirements.
Relevance to Humans and Ecosystems
Stewardship Overview: Prescribed burning of all habitat types; maintenance of adequate groundwater levels; maintenance of pollinator breeding habitat; control of livestock and other habitat degraders.
Cypripedium candidum, also known as small white lady's slipper or white lady's slipper, is a rare orchid of the Cypripedium genus. It is found in wet prairies and fens, in rich, highly calcareous soils, sedge meadow edges, calcareous roadside and railway ditches. Cypripedium candidum grows to a height of 10 to 40 cm, and blooms from early May to June. Its white pouch-like lip, sometimes dotted with maroon on the inside, is accented by tan, green or brown lateral sepals and petals. It has been known to hybridize with the small yellow ladyslipper, C. parviflorum var. makasin, resulting in the natural hybrid Cypripedium × andrewsii. The leaves and stems are slightly pubescent. The plants grow in (generally) long-lived clumps, with some clumps having up to 50 or more flowers.
Cypripedium candidum is found from Western New York, across southern Ontario to North Dakota, and south to New Jersey and Missouri. There are isolated populations of Cypripedium candidum in Connecticut, Maryland Manitoba, Virginia, Alabama, and (formerly) Saskatchewan.
Cypripedium candidum is considered rare across Canada, endangered in Ontario, and protected under the Ontario Endangered Species Act. It is believed to be extirpated from Saskatchewan. It is threatened in the United States, extirpated from Pennsylvania, endangered in South Dakota and Wisconsin, threatened in Illinois, Kentucky, and Michigan, and rare in Missouri and North Dakota. It is listed in Canada as N2, or endangered. Globally, however, it is listed as G4 (apparently secure) because there are protected sites across its entire range. It is a perennial, with horizontal, wiry-rooted rhizomes growing a few centimeters below the surface of the soil, and hence resistant to most prairie fires. It is shade-intolerant and therefore requires substantial management for invasive and woody species.
Cypripedium candidum is uncommon because it has a low seed set caused by often unpollinated flowers, as well as that its habitat of wet prairies and fens have been greatly decreased through draining for agricultural purposes. In Ontario, this orchid has never been common due to limited occurrences of fens in Cypripedium candidum's Southern-Ontario range. Habitat loss due to fragmentation through agriculture and development, suppression of fire, incursions by invasive species, especially reed canary grass (Phalaris arundinaceae), dogwood (cornus sp.), leafy spurge, St. John’s wort and buckthorn (rhamnus sp.), changes in hydrology, loss of pollinators and environmental challenges to the obligate mycorrhizae that support this species are all responsible for its decline. This ladyslipper is most intolerant of shade, and so management of remnant prairies needs to be a part of any species recovery strategies. Long-term monitoring of this species is being done through various scientific organizations, including the Chicago Botanic Garden's respected Plants of Concern program.
Like many wild orchids, this species has been further endangered by collecting for generally futile attempts at cultivation. It is now known from only two sites in the province of Ontario.
Names and Taxonomy
Comments: Distinct species.
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