Caulophyllum spp.
blue cohoshes
Eastern North America and temperate East Asia
Overview
Caulophyllum spp. is a small genus of two or three species of woodland perennials in the barberry family, Berberidaceae, native to rich deciduous forests of eastern North America and temperate East Asia. Plants rise each spring from a knotted rhizome on a single stem 1-3 ft (30-90 cm) tall, topped by large, much-divided blue-green leaves that spread into a broad, lacy canopy resembling those of meadow-rue Thalictrum spp.. New growth emerges tinted purple-blue before turning green. Small six-parted flowers in yellow-green to purplish-brown open in loose clusters in April and May, modest against the foliage. These are followed in late summer by the feature that names the plant: pairs of round, deep-blue seeds 0.3-0.4 in (8-10 mm) across that stand naked on stalks after the thin ovary wall splits away. The seeds and roots contain alkaloids and saponins that are toxic to people and animals if eaten. Plants grow slowly in cool, moist, humus-rich shade and go dormant by late summer, vanishing until the following spring.
Native Range
The genus is native to moist, shaded hardwood forests of eastern North America, from eastern Canada south to the southern Appalachians, with related species in China, Japan, and Korea. Blue cohosh C. thalictroides is the North American member, widespread in rich woods across much of the east.Suggested Uses
Blue cohosh is grown in native and woodland gardens, shaded borders, and naturalistic plantings under deciduous trees. The blue seeds and lacy spring foliage suit shade plantings with ferns and other woodlanders. It is also grown in collections of native medicinal plants.How to Identify
Appearance
Size & Dimensions
Height1' - 3'
Width/Spread1' - 2'
Bloom Information
Flowering comes early, in April and May as the leaves expand, in loose clusters of small six-parted star-shaped flowers in yellow-green to purplish-brown. The bloom is brief and easily missed against the unfolding foliage. By late summer the blue seeds have replaced the flowers and form the main display.
Detailed Descriptions
Flower Description
yellow-green to purplish-brownFoliage Description
blue-green, purple-tinted in springGrowing Conditions
Sun Requirements
Requires 1-5 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight