Featured Creature: Ladyslipper

Photo from the Bell Museum at the University of Minnesota

What creature is a forest and swamp dweller, rarely seen in the wild, and treasured for its consummate beauty?

The lady slipper, of course, or cypripedium reginae!

Photo from the Bell Museum at the University of Minnesota

The lady slipper is so named for its distinctive shape – its flowers have white upper petals and a little pouch, or labellum, of about 1-2” in length that are usually rose-pink or magenta in color. This gives it another common name of “moccasin flower.”

The plant generally grows 1-4 feet high with multiple stems, and each stem will sprout 3-5 ovately shaped green leaves.

Broad, pubescent leaves (Wikipedia)

Beloved and rare

The lady slipper is a rare wild orchid native to northern North America. It became the state flower for Minnesota in 1902 and was protected by state law there in 1925. That popularity led to its depiction in 1969 on a 6-cent U.S. postage stamp (see below). 

Lady slippers grow in wetlands such as fens, wooded swamps, and on riverbanks, such as where I lived as a small child in Beverly, MA. I remember my sense of fascinated wonder at about age 5 when we came across one of these lady slippers near the swamp behind our home; my father told us to respect its rarity and leave it alone, while appreciating how special it was to find one out there in the woods! I can still see its beauty in my mind’s eye, as I relive that wondrous sense of discovery.

In a MA fen (Wikipedia)
On a 1969 US Stamp (Wikipedia)

Reproduction and Symbiosis

In order to survive and reproduce, pink lady slippers interact with a fungus in the soil. Generally, orchid seeds do not have food supplies inside them like most other kinds of seeds. Pink lady slipper seeds require threads of the fungus to break them open and attach to them in order to pass on food and nutrients to these seeds. When the plant gets older and is producing most of its own nutrients, the fungus will then extract nutrients from the orchid roots. This sort of mutually beneficial symbiotic relationship is typical of almost all orchid species. 

Pink lady slippers flower in early to midsummer, usually with 1-2 flowers per stalk but sometimes producing 3-4 flowers. They reproduce sexually, depending on various insects that crawl into their pouches for pollination, usually in June. Their seed pods then ripen by September with up to 50,000 seeds. Though this may sound like a lot, because of low germination and an 8-16 year gap that takes place between the stages of seed and flower, the reproduction of this species is inefficient and thus uncertain. However, successful plants can live to be 20-50 years old.

Photo from MN Department of Natural Resources

Pink lady slippers require bees for pollination, which are attracted to it through deception. The bees are lured into the flower pouch through the front slit by the flower’s bright color and sweet scent. Once inside, however, the bees find no reward, and find themselves trapped, with only one point of escape. This pair of exit openings, one beneath each pollen mass, leads the bee to deposit any pollen it carries from another flower before picking up a new fresh load of pollen on its way out. But since the bees get no benefit from the plant, they also eventually learn to avoid this species resulting in very low pollination rates. 

Pink lady slippers rarely bear any fruit, but when they do it is in the form of a capsule which matures from green color to tan or brown and will split open to expose the contained seeds.

Cypripedium acaule fruit capsule (Photo by W. Cullina, Coastal ME Botanical Gardens)

Conservation Issues

Lady slippers prefer alkaline, or basic soils, so are threatened by acid rain and other sources of acidity. They are also sensitive to hydrologic disturbances, such as wetland draining, contamination, habitat loss and horticultural collectors.

Since deer seek out lady slippers as a favored delicacy, deer overpopulation can also stunt these plants’ reproduction and growth. Lady slippers are classified as imperiled or vulnerable in most northern U.S. states and Canadian provinces; in 2016, it was found at only 14 sites in Massachusetts, for example. Lady slippers are ranked as secure, however, in the Canadian provinces of Ontario and Manitoba.

Chemical and Medical Properties

The visual allure of lady slippers is slightly offset by its chemical properties, which can cause dermatitis and allergic reactions in humans due to the presence of an irritant known as phenanthrene quinone or cypripedin. However, there is a fine line between harm and help.

The Cypripedium species of lady slippers have been used in native remedies for dermatitis, tooth aches, anxiety, headaches, as an antispasmodic, stimulant and sedative, but the foliage hairs may cause a rash similar to that from poison ivy. Indeed, some orchids have swollen, ball-shaped tubers that were traditionally regarded to have medicinal value. For example, lady slipper roots were once seen as a remedy for nervousness, tooth pain, and muscle spasms, and during the 19th and 20th centuries they were used as a sedative, substituting for the European plant valerian.

So if you’re lucky enough to encounter one of these special, lovely flowers out there in the wild, please treat it with respect and savor the experience, but it’s best not to touch one of them, if only to save your skin!

By Fred Jennings