This is one of the largest and most attractive orchids in Illinois. It is more abundant than most species of orchid, although by no means common. While the flowers are in bloom, it is easy to identify this plant as a Cypripedium sp. (Lady's Slipper Orchid) because of the slipper-like lower petals. The only other species that it can be confused with, Cypripedium parviflorum (Small Yellow Lady's Slipper Orchid), has similar flowers that are smaller in size. The lateral petals of its flowers are less than 2" long, while the slipper-like lower petal is about ¾1¼" in length. The flowers of this species are more likely to be fragrant. The Small Yellow Lady's Slipper Orchid usually has a pair of leaves toward the base of the central stem, while Yellow Lady's Slipper Orchid usually has 3-6 leaves along the central stem. When this latter orchid is not in flower, it can superficially resemble Polygonatum commutatum (Solomon's Seal) and similar species in the Lily family. However, the central stem of this orchid and the upper surface of its leaves are pubescent, while the latter group of plants has stems and upper leaf surfaces that are waxy and glabrous.