Caulophyllum is a small genus of three species of perennial herbs in the family Berberidaceae (order Ranunculales), closely related to the Eurasian genera Leontice and Gymnospermium. Plants are robust and smooth, growing 0.3–0.9 m tall from underground rhizomes. Each stem bears one large (occasionally two) triple-compound leaf — an arrangement that can give the impression of several small leaves on separate branches. The leaflets are each tipped with three to five distinct lobes. Plants are exceptionally long-lived, persisting for more than 50 years in moist, rich woodland habitats.
In April or May, mature stems produce a spike of small flowers, each with six petal-like sepals ranging from greenish-yellow to purple. Six fleshy nectar glands at the base of each sepal attract insect pollinators. Differential maturity of stamens and pistils within each flower promotes cross-pollination. Fertilized flowers mature into distinctive deep-blue, berry-like fruits approximately 1 cm across, each containing two bitter seeds enclosed in a characteristic blue seed coat. The fruits persist into autumn. Seed germination is slow, often taking two or more years, and seedlings are hypogeal — the cotyledons remain underground after germination, and several additional years of growth are needed before a plant reaches flowering size.
The two North American species are C. thalictroides (blue cohosh) and C. giganteum (giant blue cohosh); the third, C. robustum, is native to Japan and eastern Asia. The genus is well known both as a spring wildflower of eastern North American forests and for its long history of medicinal use by Native American peoples. Unlike most spring wildflowers, plants are not spring ephemerals and remain visible throughout much of the summer. The blue fruits are toxic to children and the powdered root can cause dermatitis and mucous-membrane irritation.
Etymology
The genus name Caulophyllum derives from Greek kaulos (stem) and phyllon (leaf), reflecting the plant's distinctive large compound leaf appearing to emerge as a single stem-borne structure. Plants are commonly called blue cohosh, squaw root, or papoose root — names that reflect their historical use by Native American peoples to assist childbirth and regulate menstruation.
Distribution
Caulophyllum has a disjunct distribution across eastern Asia and eastern North America. C. thalictroides and C. giganteum are native to deciduous forests of eastern North America, with C. giganteum occupying a more northerly but overlapping range. C. robustum is found in Japan and adjacent parts of eastern Asia.
Ecology
Plants grow in moist, rich woodland soils, typically in the understorey of deciduous or mixed forests. The flowers are pollinated by insects attracted to six nectar glands per flower. Seeds may take two or more years to germinate, and seedlings require additional years before reaching flowering maturity. Unlike most associated spring wildflowers, plants are not ephemeral and remain leafy into late summer.
Cultural Uses
Caulophyllum has a long history of medicinal use. Various Native American tribes used the root to assist childbirth, regulate menstrual flow, and treat conditions including internal parasites, spasms, and as a diuretic. Modern herbalists continue to use it as a natural therapy. The plant also finds occasional use in woodland ornamental gardens. However, the attractive blue fruits are toxic — particularly dangerous to children — and the powdered root can cause dermatitis and irritation of mucous membranes.
