Maine has four species of lady's-slippers (Genus Cypripedium). These include the pink lady's-slipper, ram's head lady's-slipper, yellow lady's-slipper, and showy lady's-slipper. Of the four species, 2 are rare on a state-wide basis; the ram's head lady's-slipper and the showy lady's-slipper. The ram's head lady's-slipper is also globally rare. Please see our Rare Plant List for the complete listing of all rare plants in Maine.
The lady's-slipper orchids are among the showiest orchids in the eastern United States and are vulnerable to collection. Lady's-slippers require highly specific habitats in order to grow, thus collecting lady's-slippers, even the common ones, is discouraged. Over-collecting of lady's-slippers could make even the common species rare over a short time period.
Lady's-slippers have a specific association with a beneficial fungus known as mycorrhizae. This fungus in the soil allows the lady's-slippers to obtain valuable nutrients and energy from organic matter that would otherwise be unattainable. This association is especially beneficial for the germination and seedling stage of lady's-slippers growth, allowing the seedlings to obtain more nutrients and energy than what are available from the tiny seed.
Left: Cypripedium acaule, typical pink form; Right: C. acaule, white form, photo by C. Pendergast
Pink lady's-slipper is the most common lady's-slipper in Maine. Blooming through June, it is typically found thinly scattered in the understory of dry, mixed woods and boggy areas. Pink lady's-slipper produces a pink (occasionally white), 1 to 3 inch long pouch-like flower that grows singly on a stalk emerging from 2 broad, fuzzy leaves at the base of the plant.
Yellow lady's-slippers are uncommon in Maine. As the name implies, this species is best identified by the yellow pouch-like flowers that bloom from late May through mid July. Unlike the pink lady's-slipper, the yellow lady's-slipper has leaves along the stem of the plant and the flower is sometimes fragrant. In Maine, yellow lady's-slippers are found in mesic (moderately moist) nutrient rich forests as well as in bogs and swamps.
This is Maine's largest lady's-slipper. The plant has become increasingly rare due to over collecting and habitat reduction. It has a tall, leafy stem that bears 1-2 white-petaled flowers with a brilliant pink pouch, blooming in late June and into July. It is found in constantly moist habitats, including cedar swamps and cedar glades. It prefers a pH near neutral and some sunlight. The plant's hairs along the stem and leaves may cause a rash on the skin similar to that of poison ivy.
Known from only a handful of sites in Maine, this is our rarest lady's-slipper as well as a globally imperiled plant (ranked G3). This species is identified by its small reddish-veined lower lip on the flower blooming in late May through mid June. The flower has 3 separate sepals (all other lady's-slippers have 2) and the plant has 3-4 leaves. It prefers cool, moist, partially shaded, acidic areas, most often in northern white cedar swamps with well drained soils.