Each shoot has up to four leaves and a small number of flowers (typically one or two), which have long often twisted petals varying from red-brown to black (rarely green) and a slipper-shaped yellow labellum, within which red dots are visible.

[5] Cypripedium calceolus can be confused, when not flowering, with Allium ursinum, Convallaria majalis or several species of Epipactis orchid.

Chromosome number has been given as 2n=20 but also 2n=22[7] It has a widespread distribution from Europe east through Asia from Spain to the Pacific, including almost every country in Europe plus Russia (European Russia, Siberia, and the Russian Far East), northeastern China (Heilongjiang, Jilin, Liaoning, Nei Mongol), Mongolia, Korea and Rebun Island in Japan.

Other suggested mycorrhizal partners include Alternaria sp., Ceratorhiza sp., Chaetomium sp., Cylindrocarpon sp., Epicoccum purpureum, Epulorhiza sp., Moniliopsis sp., Mycelium radicis atrovirens, Phoma sp.

[13] Although the global conservation status of Cypripedium calceolus is least concern according to the IUCN Red List,[1] in many countries (including the UK and Denmark) it has become rare and is afforded legal protection.

[15] While the virtual extinction of the lady's-slipper orchid from its historical range in Britain is often blamed on uprooting by gardeners and botanists, it is also the case that its preferred habitat shrank markedly with human clearance of woodland from the limestone landscape, and the grazing of sheep will have finished it off.

[1] Archived 2021-04-18 at the Wayback Machine Cypripedium calceolus has appeared on postage stamps in a huge number of countries including Austria, the Czech Republic, Denmark, France, Grenadines, Hungary, Italy, Latvia, Madagascar, Moldova, Mozambique, Norway, Romania, Russia, Slovenia, Sweden, Uganda, Ukraine and the United Kingdom.