Wildflower Wednesday — Blue Cohosh

Caulophyllum thalictroides

The seed coats of blue cohosh seeds become blue over
a prolonged period from August through September so
that some are always attractive to birds during the
time of fall migration. © 2012 Carol Gracie.


Blue Cohosh – A Deceptive Plant

The flowers of blue cohosh (Caulophyllum thalictroides) don’t attract much notice in spring. They are small and rather dull yellowish-green or purplish-brown. However, they bear looking at with a hand lens to better appreciate their strangely modified, fan-shaped petals that serve as glistening nectaries. The nectaries attract insect pollinators—in this case, various species of flies. What appear to be petals are actually the flower’s sepals.

It is the “fruit” that attracts the eye in late summer and autumn. The term “fruit” is put into quotation marks because what appear to be juicy blue fruits (from which the plant gets its common name) are actually the seeds of the plant with bright blue seed coats. By appearing to be fruits, the seeds appeal to birds at the time of migration, when they need a good source of fuel to continue their southward journey. Birds eat the “fruits,” gaining no energy from them, and excrete them further along their route, thus serving as dispersal agents for the plant.

k9668Read more about blue cohosh and other spring wildflowers in Carol Gracie’s book, Spring Wildflowers of the Northeast: A Natural History.