Cypripedium candidum Muhlenberg ex Willdenow (White lady’s-slipper orchid), a brief summary of the species status in Illinois.

Paul B. Marcum

Cypripedium candidum (White lady's-slipper orchid) in hand for scale. The smallest lady's slipper in Illinois and one of the smallest in North America.

Lady’s-slipper orchids are a joy to behold! There are approximately 45 species of lady’s-slipper orchids (genus Cypripedium) in the world. They are found nearly throughout the Northern Hemisphere, but especially in temperate Eurasia and North America. Of the approximately 15 taxa in North America, the White Lady’s-slipper orchid (Cypripedium candidum) is one of the very smallest (Sheviak 2002). The whole plant is often only 15-25 cm tall and the tiny lip or namesake slipper part of the flower is only 17 to 27 mm long. For comparison, the slippers of some of its eastern North American relatives (Large yellow lady’s-slipper orchid, Cypripedium parviflorum var. pubescens and Showy lady’s-slipper orchid, Cypripedium reginae) are usually more than twice as long. White lady’s-slipper orchids can be very difficult to find when they are not in flower and may lay hidden under overhanging vegetation. Fortunately, they usually grow in small clusters of many flowering stems, sometimes upward of 50. Look for White lady’s slipper orchids in alkaline wetlands, usually fens, wet-mesic prairies, or around the edges of sedge meadows. Be prepared for wet knees as your search may require crawling to find and inspect the flowers up close. Flowering usually occurs in mid- to late-May with extreme flowering records as early as late April and as late as mid-June.
 
Although NatureServe designates White lady’s-slipper orchids as globally secure (G4), this species is currently rare to uncommon throughout its range. It has been recorded in 18 eastern U.S. states, mostly in the northeast and northcentral parts of the country, with isolated records from Alabama. White lady’s-slipper orchid is Presumed Extinct (SX) in Pennsylvania, Critically Imperiled (S1) in South Dakota, Nebraska, Missouri, Kentucky, Alabama, Virginia, New York, New Jersey, and Maryland, Imperiled (S2) in North Dakota, Wisconsin, Illinois, Michigan, and Ohio, and Vulnerable (S3) in Minnesota, Iowa, and Indiana (NatureServe 2020). Unfortunately, this once widespread and at least occasionally encountered species has suffered a drastic decline in population numbers. The primary reasons are habitat loss, invasive species, woody encroachment, and outright poaching. NOTE: NEVER REMOVE ANY NATIVE PLANTS FROM REMNANT SITES UNLESS THE POPULATION IS THREATENED WITH CERTAIN DESTRUCTION. Naturally occurring remnant plant communities are invaluable and represent years of crucial interaction and relationships among its inhabitants (plants, animals, fungi) and the environment. For many species, these conditions cannot be easily created. Cultivation of lady’s slipper orchids require very specific conditions and significant knowledge and most efforts to cultivate lady’s-slipper orchids in a home garden or even in a restoration area will result in death of the plants. Please, don’t do that. Also, only purchase native plants, especially rare species, from reputable dealers that are growing and actively propagating the species.

A clump of White lady's-slipper orchids, approximately 20 cm tall.

In Illinois, White lady’s-slipper orchid has a similar story. It was once widespread and at least occasionally encountered. Records stored in herbaria throughout Illinois and across the country document this species from 25 counties across the north half of the state (Herkert and Ebinger, eds. 2002). Unfortunately, many of these populations were lost very early as Illinois was settled. Widespread conversion of land for agriculture has all but extirpated the species from downstate Illinois. Mohlenbrock (1970) stated “this species, along with the Yellow lady’s-slipper and the Showy lady’s-slipper, were not infrequent in the state before 1900. Indiscriminate collecting, however, has made all of these species rare in Illinois to the point of extinction.” Additional population losses accumulated over time and, by 1981 when the inaugural Illinois rare plant list was published, this species was listed as endangered within the state. Fortunately, this is when the story started to change for this tiny endangered plant. Since 1981, many populations have been discovered and protected in numerous state nature preserves, county forest preserves, and on private land. People care and started to protect and care for our remnant natural communities. Natural community restoration and habitat management started to become a widespread and common practice and the results were being seen on the ground. By 1999, things were starting to improve for White lady’s-slipper orchids and the species was downlisted from endangered to threatened. With White lady’s slipper orchid specifically, habitat management in the form of prescribed burning, invasive species management, and removal of encroaching woody species has had a tremendous positive impact on populations. Staff and volunteers with the Chicago Botanic Garden’s Plants of Concern Program (POC) have monitored this rare species for several years and to date have monitored more than 50 populations. Increased fire on the landscape, coupled with other management, has resulted in population increases at many sites and in 2015 White lady’s-slipper orchids were officially delisted in Illinois.

Of course, the story doesn’t end here. Continued vigilance and care are needed. Natural remnants must always be protected and cared for. In Illinois, most downstate populations have been lost but a few remain intact. Let’s expand on the work that has occurred in northeast Illinois and do what we can to save this species throughout Illinois and throughout its range.

All photos from northeast Illinois, wet-mesic prairie over dolomite, May 24, 2020.

Literature Cited and References:

Herkert, J.R. and J.E. Ebinger, editors. 2002. Endangered and Threatened Species of Illinois: Status and Distribution, Volume 1 – Plants. Illinois Endangered Species Protection Board, Springfield, Illinois. 161 pp.

Mohlenbrock, R.H. 1970. The Illustrated Flora of Illinois, Flowering Plants, Lilies to Orchids. Southern Illinois University Press, Carbondale and Edwardsville, Illinois. 288 pp.

NatureServe. 2020. NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available at https://explorer.natureserve.org/. (Accessed: June 5, 2020).

Plants of Concern. 2020. Plants of Concern, a project of the Chicago Botanic Garden. Plants of Concern, Chicago, Illinois. Available at https://plantsofconcern.org/our-policies. (Accessed June 5, 2020).

Sheviak, C.J. 2002. In: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 19+vols. New York and Oxford. Vol. 26.