Endangered Plants of Ontario - Small White Lady's-Slipper

Small White Lady's-Slipper

Cypripedium candidum

Status

Rare in Canada, endangered in Ontario and protected under the Ontario Endangered Species Act, believed extirpated from Saskatchewan; threatened in the United States, extirpated from Pennsylvania, endangered in South Dakota and Wisconsin, threatened in Illinois, Kentucky, and Michigan, rare in Missouri and North Dakota.

Range

Western New York, across southern Ontario to North Dakota, south to New Jersey and Missouri; isolated populations in Connecticut, Manitoba, and (formerly) Saskatchewan.

Habitat

Wet prairies and fens, in rich, highly calcareous soils.

Height

10 to 40 cm.

Bloom Period

May and June.

Factors contributing to its status

Small white lady's-slipper is at the eastern and northern limits of its range in the southern part of the Great Lakes region.

Its flowers often remain unpollinated, and consequently seed set is often low.

It has never been common in Ontario, because of the limited occurrence of fens in the southern part of the province. (Even if undisturbed by human activity, some fen habitats may become unsuitable through natural succession.)

Its habitats have been greatly decreased by the draining of fens for agricultural purposes.

Lady's-slippers have narrow habitat tolerances and complex, mutually dependent relationships with microscopic soil fungi, and therefore have difficulty establishing new populations even in seemingly suitable habitats. 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.

Notes

Lady's-slippers are pollinated by small bees, which are first attracted by scent, and then directed by the slipper's morphology through a "one-way" route that assures cross-pollination. As a bee moves through the slipper, its back first contacts the stigma, depositing any pollen from a previous visit to another flower, and then contacts the anthers, from which new pollen may be deposited on its back.

Habitat	Wet prairies and fens, in rich, highly calcareous soils.
Height	10 to 40 cm.
Bloom Period	May and June.
Factors contributing to its status	Small white lady's-slipper is at the eastern and northern limits of its range in the southern part of the Great Lakes region. Its flowers often remain unpollinated, and consequently seed set is often low. It has never been common in Ontario, because of the limited occurrence of fens in the southern part of the province. (Even if undisturbed by human activity, some fen habitats may become unsuitable through natural succession.) Its habitats have been greatly decreased by the draining of fens for agricultural purposes. Lady's-slippers have narrow habitat tolerances and complex, mutually dependent relationships with microscopic soil fungi, and therefore have difficulty establishing new populations even in seemingly suitable habitats. 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.
Notes	Lady's-slippers are pollinated by small bees, which are first attracted by scent, and then directed by the slipper's morphology through a "one-way" route that assures cross-pollination. As a bee moves through the slipper, its back first contacts the stigma, depositing any pollen from a previous visit to another flower, and then contacts the anthers, from which new pollen may be deposited on its back.