The most common lady's-slipper and with the widest range of habitats. In every province in Canada, it can be found in boreal forest, bogs, open swamps and alongside streams.

The most variable of the yellow ladyÕs-slippers is difficult to describe as size and shape of the flower and plant are affected by location.
Height to 80 cm.
Leaves: 3 - 5, bright green, ovate-lanceolate, plicate, sheathing the stem.
Flowers: 1 - 2, large, often 54mm. Petals unmarked to spotted to rarely extensively blotched with reddish-brown.
Moderate scent. Sheathing bract is densely and conspicuously silvery pubescent when young. Plants in the far north or in exposed conditions can have flowers as small as 20cm. Plants located in limestone areas are frequently clump-forming.

Keys to separating this species from the others are the size of the plant and flower, the colouration of the petals, the scent and the pubescence of the sheathing bract.
The lip is compressed laterally in the large lady's-slippers; whereas, it is compressed vertically in the smaller varieties.

1994 AOS Bulletin 63(6): 664-669
1995 AOS Bulletin 64(6): 606-612
The Genus Cypripedium
The Native Orchids of the United States and Canada excluding Florida
The Canadian Field-Naturalist Vol III-1
The Orchids of Bruce & Grey