Caulophyllum thalictroides (Blue Cohosh)

Britton, N.L., and A. Brown. 1913.  An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner’s Sons, New York. Vol. 2: 128. Provided by Kentucky Native Plant Society. Scanned by Omnitek Inc

Where Commonly Found:   Extremely rare in RI, but otherwise present in our region.  Floodplains and forests

How to Identify:
(For unfamiliar words: Wikipedia Glossary of Botanical Terms).
Go Botany Key for Caulophyllum thalictroides.
Illinois Wildflower’s description of Caulophyllum thalictroides. Click on more images.

Flower Color:  Depending upon eco-type can be greenish yellow, greenish purple or greenish brown.
Flower Type:  Panicle
, 1″-3″ longs, rounded or elongated with 5-30 flowers.  Each flower is about 1/3″ across with 6 sepals, 6 stamens and an ovary with a beak-like style.  There are 3-4 green sepal-like bractlets beneath the flowers.
Flower Time:  Mid-Late Spring before leaves fully develop.
Leaf Arrangement:  Alternate, one leaf per node along unbranched central, light green to pale purple, glabrous and often glaucous, stem. There is only a single compound leaf, near the top of the plant, when not in flower.  When in flower there are two compound leaves.  The lower compound leaf is divided into a whorl of 3 compound leaflets, each with 9 sub-leaflets arranged in groups, 2 laterally and one terminal .  Occasionally the compound leaf may be divided into 15 simple sub-leaflets.
Leaf Type:  Compound, (see Leaf Arrangement above).  Upper surfaces can be anything from gray-green, yellowish green or medium green.  Lower surfaces in pale green and glabrous.
Height: 1′ – 3′
Seed Collection:  AS THIS PLANT IS RARE OR ENDANGERED IN PARTS OF OUR REGION PLEASE FOLLOW GUIDELINES BY THE CENTER FOR PLANT CONSERVATION.  Seeds are fleshy, berry-like, about 1/3″ across, globoid, glabrous and glaucous.  Starting off green and becoming bright blue at maturity.

Use:  Naturalizing woodland garden.
Light:  Part to Full Shade
Hardiness Zone:  3 – 8 USDA Zone Map
Soils:  Medium, but not drying out.
Notes:  Showy berry-like fruit, POISONOUS TO CHILDREN,  plant is slow to establish, will take 3 years to flower from seed.  All parts of the plant can cause skin irritation.
Native to:  New England and NY States, rare in parts of RI, native to most of eastern, southern and mid-western US.  Biota of North American, North American Plant Atlas. 


Requested by Bronx River Wildflower Corridor, Roseanne Andrade.

Blog at

Up ↑

%d bloggers like this: