Classification Hierarchy
Kingdom Plantae
Subkingdom Tracheophyta
Superdivision Spermatophyta
Division Magnoliophyta
Class Magnoliopsida
Subclass Magnoliidae
Order Ranunculales
Family Berberidaceae
Genus Caulophyllum
Species Caulophyllum thalictroides
Blue Cohosh

Date: April 21, 2010. Location: Amana Woods (map)

BONAP, FNA, ITIS, USDA, VPI

Scientific Name: Caulophyllum thalictroides ([Gr] caulos - stem; phyllon - leaf; thalictroides - the leaf shape is similar to Thalictrum (Meadow-rue))
Common Name: Blue Cohosh
Origin: Native Habitat: Rich woodlands, shade
Notes: The roots and raw blue seeds from this plant are listed as poisonous (see ref. #1 and #5). Herbal preparations from blue cohosh have been used to induce labor but there are reports
of dangers to the newborn (ref. #10).
Additional references: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12.

Field Marks for Identification:

Flowers: April; The inflorescence is a panicle of small yellow/green flowers (~ 1 cm. each) The flower parts are 6,6,6,1 (sepals, petals, stamen, pistil) with three or four small bractlets at the base behind the yellow/green sepals. The petals are small, thickened, gland-like, with a narrow base (claw) at the point of attachment. The size and claw of the petal is much smaller than that of the sepal. Swink and Wilhelm describe the fruit and seed development thusly:

The ovary wall ruptures early in development by the pressure of the two erect enlarging seeds and withers away. A naked seed is exposed on an expanded stalk, and develops a fleshy outer integument that simulates a drupe. This integument is an iridescent blue which beggers description.

Leaves: A large triternately compound sessile leaf arises on a single glabrous stem about a foot above the ground. The leaflets are petioled, often terminating in two or three acute lobes.

Glossary: Botanical Terms pdf

Blue Cohosh-1 Blue Cohosh-2 Blue Cohosh-3 Blue Cohosh-4