Northern Prairie Wildlife Research Center
Northeast Wetland Flora
Field Office Guide to Plant Species
Cypripedium acaule Ait.
- Family: Orchid (Orchidaceae)
- Flowering: April-July
- Field Marks: This is the only lady's-slipper orchid that has a leafless flowering stalk with 2
leaves at the base of the plant and a rosy-pink lip petal.
- Habitat: Bogs, wet woods, acid woodlands.
- Habit: Perennial herb with thick, fibrous roots.
- Stems: Upright, unbranched, leafless, up to 1 1/2 feet tall, glandular-hairy.
- Leaves: 2, basal, broadly elliptic, up to 10 inches long, up to 6 inches wide, glandular-hairy,
- Flowers: Borne singly at the tip of the leafless stem, up to 3 inches long.
- Sepals: 3, united, unlike, the upper one narrowly lanceolate, greenish brown to greenish purple, up to
2 inches long, up to 3/4 inch wide, the lateral two up to 1 3/4 inches long, up to 1 1/4 inches wide,
greenish brown to greenish purple.
- Petals: 3, unequal, the 2 lateral ones lanceolate, greenish brown, hairy on the inner face, scarcely
twisted, up to 2 1/2 inches long, up to 3/4 inch wide; lip petal pouch-shaped, drooping, pink or rose,
up to 3 inches long, with a deep cleft down the middle.
- Stamens: 2.
- Pistils: Ovary inferior.
- Fruits: Capsule ellipsoid, up to 2 1/2 inches long.
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