This showy perennial member of the orchid family has a large lemon-yellow flower with an inflated pouch-like lip ("slipper"), often streaked or dotted with purple spots. The lower inflated petal is about 1.5 to 2 inches long. The sepals and lateral petals are greenish-yellow or purple. The lateral petals are twisted spirally. There are two greenish yellow sepals, one above and one below the lip. The lower sepal actually consists of two united sepals. There are two varieties in the state. The large yellow lady’s slipper is variety pubescens has yellower and less twisted petals and less fragrance than the small yellow lady slipper (variety parviflorum). There is considerable variability of form between the two varieties and proper identification is not always easy.

The plant grows 1.5 to 2 feet tall in moist, rich rocky woods, slopes, swamps and bogs. It is found from Quebec and Newfoundland south to Missouri and to Georgia in the mountains. In Pennsylvania the status of large yellow lady's-slipper is considered vulnerable, though it has a wider distribution that the small yellow lady's-slipper (classified as Endangered in the state). The blooming period is April to June. Another common name for the species is moccasin flower. The stem is leafy bearing 1 or 2 flowers. The 3-5 leaves are up to eight inches long and have parallel veins. The fine hairs on the stem may cause skin irritation. Some botanists consider both varieties as separate species and distinct from the European varieties. Others consider the pubescens as a variety of Cypripedium parviflorum so the classification of this group of plants is very muddled. The large yellow lady’s slipper can grow well in a proper garden setting, but should never be transplanted from the wild.