In this installment of What’s Poppin’ let’s talk about the stunning wildflower, Cypripedium acaule or Pink Lady’s Slipper. Pink Lady’s Slipper, also commonly called the Moccasin Flower, is a species within the Orchid family (Orchidaceae) that can be found throughout the Chesapeake Bay watershed and blooms from May to July.

Species belonging to the Orchid family usually are epiphytes. This means that the orchid root system is not attached into the soil; the plant can instead be supported by growing on another plant, rock or other structure. Water and nutrients are obtained by the rain, vapor, and debris that falls atop the leaves. Pink Lady’s Slippers are distinct in that they are terrestrial orchids (it’s reported that less than 1% of orchids, or about 200 of the 28,000 orchid species, are terrestrial). Terrestrial orchids will be found on the ground where they will root into humus. They maintain specialized underground storage organs that are usually described as a ball-shaped tuber, short and thick rhizome, or round corm; all of these structures allow for nutrient storage.

Five pink lady's slippers flowers growing up from the same plant on a forest floor surrounded by moss, dead leaves, and rocks.

A cluster of the terrestrial orchid (Photo credit: Christine Danforth).

This alluring species will produce enormous numbers of extremely small seeds that lack significant endosperm, so the plant has evolved a symbiotic relationship with fungus to allow germination and receive energy. It has been described that a thread from the fungus Rhizoctonia will break through the seed coat and attach itself to the embryo in order to pass nutrients until the plant is mature enough. Once it can effectively support itself, the Pink Lady’s Slipper will supply nutrients to the fungus through its roots; a mutually beneficial relationship is now occurring. The plant is also understood to reproduce vegetatively (clonally) through the plant’s underground storage organ. The plants can live over 30 years and may experience dormancies based on year-to-year stressors.

Pink Lady’s Slippers are self-compatible (can be fertilized by its own pollen), but require insects for pollination. The beautiful pink labellum, or sac, attracts pollinators. Once an insect enters the labellum it can rarely exit the same route. If the insect is the proper size it will pick up pollen as it navigates to the exit; it will exit through the basal orifices (adjacent to where the male reproductive parts are) effectively depositing pollen on the male organs. It is reported that bumble bees are some of the leading pollinators among the Hymenoptera that visit the flower.

If you see something blooming, leafing out, ripening, or otherwise changing in your woods, send us photos ( to include in next month’s Forests for the Bay newsletter for more phenological fun!