Cypripedium acaule - Pink Lady's Slipper Orchid/Mocassin Flower

Phylum: Magnoliophyta - Class: Liliopsida - Order: Orchidales - Family: Orchidaceae

Cypripedium acaule

This orchid, which is also known as Stemless Lady's Slipper, is widespread across Canada and the United States.


An unmistakeable orchid, Cypripedium acaule grows to around 40cm in height. It has a distinctive pair of deeply keeled basal leaves and each stem carries a large, deep-pink slipper-shaped flower. A white form, Cypripedium acaule forma alba is also recorded.


The distribution of the Pink Lady's Slipper is centred on the northeastern United States - the high zones of the Appalachian Mountains, the Great Lakes area, northern Ontario and Newfoundland.


The main habitat of Pink Lady's Slipper is coniferous forests, but it is tolerant of other habitats and sometimes apperars in meadows, roadside ditches, bogs andsand dunes - and even on railway sidings and cuttings.

Side view of Pink Lady's Slipper Orchid

Flowering times

This orchid has a long flowering time, and individual flowers can remain in good condition for over three weeks in a cool season. Beginning in May, Pink Lady's Slipper flowers are often found well into June, at which time in good sites these lovely flowers carpet the ground.

In Europe, our closest relative to the Pink Lady's Slipper Orchid is the Lady's Slipper Orchid Cypripedium calceolus. In the UK, the known native plants were reduced to just one specimen in Yorkshire. Today the Lady's Slipper Orchid is the subject of a re-introduction programme which is taking place at Gait Barrows National Nature Reserve in Lancashire.

In other northern European countries, including Sweden, Norway, Finland, Denmark, Austria and Switzerland, the Lady's Slipper Orchid still flowers relatively freely, but it cannot be described as common anywhere in its range.


The genus name Cypripedium comes from the Greek Kypris, meaning 'Venus', and podilon, meaning 'slipper'. The specific epithet acaule means 'without a stem'.


Photographs by kind permission of Gareth and Margaret Howell.

Close up of Pink Lady's Slipper Orchid

Reference sources

The Plant List

Philip E Keenan (1998) Wild Orchids Across North America, Timber Press Inc.

Sue Parker's latest ebook is a revised and enlarged edition of Wild Orchids in The Burren. Full details here...

Buy it for just £5.95 on Amazon...

Sue Parker's new ebook is a comprehensive and fully revised edition of her acclaimed field guide to the Wild Orchids of Wales. Full details here...

Buy it for just £5.95 on Amazon...

Sue Parker's 5-star acclaimed field guide to the Wild Orchids of the Algarve is now available as an ebook. Full details here...

Buy it for just £5.95 on Amazon...

Please Help Us: If you have found this information interesting and useful, please consider helping to keep First Nature online by making a small donation towards the web hosting and internet costs.

Any donations over and above the essential running costs will help support the conservation work of Plantlife, the Rivers Trust and charitable botanic gardens - as do author royalties and publisher proceeds from books by Pat and Sue.

© 1995 - 2024 First Nature: a not-for-profit volunteer-run resource

Please help to keep this free resource online...

Terms of use - Privacy policy - Disable cookies - Links policy