Cypripedium parviflorum pubescens (syn. Cyp. calceolus pubescens)

Common names:  Large Yellow Lady’s Slipper

Range:  Widely distributed throughout most of the US and Canada

Bloom season (in Ohio):  early to mid May

Habitat:  This species grows mostly in rich woodlands, but can also be found growing on the edges and elevated areas of bogs and fens.  It prefers a pH between 5.0 and 7.0.  It grows in light dappled shade. 

Comments:  This is the widest ranging and most variable Cypripedium in North America.  Plants can grow up to two feet tall, and the petals of the flower may spread more than six inches across.  The petals and sepals of the flower can vary from pale green to rich mahogany, but the lip is always bright yellow.  Individual plants also vary in the angle that the lateral petals are held, and the amount of twist in the petals. 

There is considerable botanical debate on whether the North American yellow lady’s slippers should be considered the same species as the European Yellow Lady’s Slipper (Cyp. calceolus).