White lady's slipper

2017 species of the year

White lady's slipper (Cypripedium candidum).   Photo courtesy of Kitty Kohout.

White lady's slipper

(Cypripedium candidum)

White lady’s slipper (Cypripedium candidum) is one of the 48 species of orchid found in Wisconsin (47 native and one non native) and only 12 lady's slippers in North America. It is also one of our earliest blooming orchids, flowering in mid-May to early June. Because the flowering window is fairly small, this beautiful wildflower is a perfect candidate for the species of the year. In order to survey as many known sites as possible, we will need as many rare plant monitors in the field as possible while the orchids are actually blooming

White lady’s slipper was listed as threatened in Wisconsin in 1979, the first year a list of endangered and threatened plants was published. The species is threatened, primarily by destruction and degradation of its wet, calcareous prairie habitat, though poaching and herbivory may play a smaller role. It's known from 73 sites in Wisconsin, mostly in the southeast quarter of the state, but at least two of these populations have been extirpated and 24 have not been reported in over 40 years. A time frame half that long would be enough for shrubs and invasives species to encroach or a small population to simply wink out.

Despite being considered vulnerable across much of their range, the Upper Midwest is a stronghold for white lady's slippers. Recent surveys in Minnesota and Illinois have found it is more secure than previously thought. With the help of rare plant monitors we will gather enough information to be able to conduct a statewide status assessment of this species in the very near future, adding to the conservation picture being developed by adjacent states


White lady's slipper clump

Clump of small white lady's slipper.   Photo credit: Wisconsin DNR Staff

Small white lady's slipper grows in clumps where many stems arise from more or less the same point. On your data sheet, this clump could be considered one individual.

White lady's slipper pouch

Pouch of small white lady's slipper.   Photo credit: Thomas Meyer.

The pouch of small white lady's slipper is often spotted or streaked with purple. Hybrids can occur between white and yellow lady's slippers. The pouches of these hybrids are typically creamy, an intermediate color between the two parents.

White lady's slipper

Small white lady's slipper.   Photo credit: Drew Feldkirchner.

The white "slipper" may be called a lip, labellum, or pouch in various plant keys. There are usually a combined four petals and sepals situated around the lip and which appear very similar. The petals are usually yellowish green and often striped with maroon and twisted. A top and bottom sepal are found above and below the lip and are of a similar color and shape as the petals.

White lady's slipper range map

Range map for white lady's slipper.

Small white lady's slippers are found most commonly in southeast and central Wisconsin, where calcium rich groundwater percolates through glacial outwash deposits and from morainal slopes. Populations are much less common in southwest Wisconsin. A collection from Boscobel in 1885 is the furthest west the species has been found here.


Each year the Rare Plant Monitoring Program will pick a plant species that we believe deserves special attention. The goal for the "species of the year" effort is to survey all known populations in a single growing season. Rarely are we able to gather comprehensive information on a single species like this, which makes assessing the statewide population of the species difficult. These comprehensive surveys will allow monitors to build a search image for the target species and reinforce that image with multiple surveys across different sites. Monitors will be able to get a better sense for what habitat the species is found in and what habitat features (associated plants, canopy cover, soil type, etc.) may indicate suitable habitat.

Monitors are not required to survey for the species of the year. In fact, depending on its spatial distribution, significant travel may be necessary to conduct a survey for the species of the year. The "species of the year" is meant to give a little bit of structure to the program and allow monitors to become more familiar with one species. If you’re interested in searching for the "species of the year" contact the program coordinator to get a survey assignment.