Blue Cohosh

Caulophyllum thalictroides


Also known as Yellow Ginseng, this woodland perennial has three seasons of interest! Smoky purple stems and yellow flowers in spring, attractive foliage and pale blue seeds in summer followed by bare stalks with cobalt colored seeds in autumn. The roots of this slow-to-establish native have been used historically for medcinal purposes to the point of overharvesting. It favors damp soil and is often found along floodplains and in forests. As it resents disturbance once established, it is best to plant this long-lived beauty in an ideal location where it can be left in place.


Other Common Names: Blue Cohosh, Yellow Ginseng, Blue Ginseng, Papoose Root, Seneca Root, Blueberry Root

Family: Berberidaceae

USDA Zones: 3 – 8

Life Cycle: Herbacious Perennial

Height: 1.00′ – 2.00′

Spread: 0.50′ – 1.00′

Sun: Part Shade – Full Shade

Soil: Rich Humus, Moist Loam, Neutral to Slightly Acidic, Abundant Organic Matter

Moisture: Medium – Medium Wet (Consistently Moist, Does Not Dry Out)

Bloom Time: April – May

Bloom Color: Pale Yellow – Yellow Green

Uses: Naturalize, Woodland Garden

Native Range: BONAP Map

Native Range Color Key: Dk. Green = Present in State and Native, Lt. Green= Present and Not Rare, Yellow = Present and Rare, Gold = Not Present in State, Teal = Present and Exotic, Cross-Hatched = Questionable Presence


  • Seeds can take 2-3 years to germinate
  • Blooms do not occur for several years after germination
  • Extremely slow to establish; can resent disturbance
  • Historically overharvested for it’s roots (used medicinally)
  • Considered a threatened species in Rhode Island
  • Seed formation begins April/May; matures August/September
  • Berry-like seeds are toxic; not for human consumption
  • No serious pests/diseases; leaves scorch in too much sun
  • Deer & rabbit resistant; browsing avoided by most mamalian herbivores due to leaf toxicity
  • Must have shady, moist, fertile, woodland conditions (no direct afternoon sun)
  • Leaves can be confused with Tall Meadow Rue (Thalictrum pubescens) – generally Blue Cohosh leaves are much larger and foliage starts midway up the stem. Meadow Rue leaves are smaller/lacier and foliage starts from the ground up.



Blue Cohosh emerges before the leaves appear on the trees. It has smoky blue/purple stems and curled foliage. Anywhere from five to thirty tiny flowers (0.33″-0.50″) are produced in April or May.
Foliage starts midway up unbranched stems. Many individuals form a small colony.
April 28, 2020 – Early stages. Only plants that are several years old will have blossoms.
May 13, 2020 – As spring progresses, stems and foliage turn blue-green in color. Blooms have six petal-like sepals and six small petals. Each petal contains nectar glands providing a food source for early bumblebees and flies.
June 8, 2020 – Blue Cohosh mingles with Jewelweed and young Northern Spicebush saplings. Newly developing seeds are green and gradually transition to pale powdery blue.
July 27, 2020 – Though resembling berries, these are actually “naked seeds”. Toxic and not for human consumption! They do not have a soft and juicy interior. Rather, it is a very large single brown seed with a papery thin blue outer seed coat.
September 2, 2020 Cobalt blue seeds are mature. The outer coat shrivels with age.
Leaves fade in late summer after a season of droughtlike conditions. Mature seeds remain on sturdy upright stems throughout the fall season.
Seeds harvested in early September. The outer seed coat was removed to reveal dull brown seeds. After being thoroughly cleaned with a dozen water bath rinses, they shine! Always collect wild seed responsibly or purchase from a reputable source.


In order to provide the maximum benefit to pollinators, it is best to plan for a succession of blooms. This ensures that as one species fades, another begins to blossom. In this way, a constant source of nectar and pollen is provided from spring through fall. The following natives enjoy similar growing conditions to Caulophyllum thalictroides:


Can’t get enough of this stunning native plant? We can’t either! Here are more photos to enjoy.

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