Blue Cohosh is a native erect perennial forb growing from one to over two feet high on smooth mostly cylindrical stems, unbranched below the inflorescence.
The leaves differ between plants that flower and those that do not. Non-flowering plants produce a single compound leaf at the top of the stem. Flowering plants produce a second leaf from the middle of the stem that is usually somewhat larger than the first leaf which, in a flowering plant, is located directly under the inflorescence. The leaves have from 3 to 4 (3 usually) 3-part sections, each section then divided into 3 sub-sections which are in turn divided into 3 egg shaped leaflets that when mature have several prominent lobes at the top - usually 3 but up to 5. [Thus 9 leaflets per section and 27 leaflets per leaf.] The leaf rising from above the middle of the stem is the reason for the genus name. At first they are a smoky-green then turning to a light to medium bluish-green; they are without hair and have pinnate to palmate venation. Leaves are easily detached from the stem.
The inflorescence is a branched terminal cluster, called a cyme, at the top of the stem and above the main leaf, containing 5 to 70 flowers, but usually less than 30.
Flowers: The entire individual flower is very small - only 3/8 to 1/2 inch wide. The 6 sepals of the flowers are of green to purplish color; these are elliptical in shape with the tip somewhat flexed backward and look like petals, except that the petals are actually tiny, appearing at the base of the longer sepals. They have a fan-shape, are greenish-yellow and bear nectar. The 6 stamens are symmetrical (not alternate) with the petals and sepals and have short greenish-yellow filaments and a two-section yellow anther. Thus, each sepal lines up with a petal and a stamen. The ovary is ovoid with a single style. Under the flower are 3-4 small bractlets that look like sepals but soon drop away.
Fruit: Each fertile flower produces 2 fleshy berries, about 1/3 inch wide which contain a round brown seed. "Blue" refers to the color of the fruit which forms in early summer and stays on the plant till the following spring unless eaten. Fruit color is first green but darkens over the summer into blue and by late fall and early spring, if still present, is quite striking. The seeds are best planted in the fall and let nature handle the germination requirements, which may take some time..
Habitat: Blue Cohosh grows from a somewhat lumpy rhizome. It is an early spring flowering plant that blooms in the dappled sunlight under the tree canopy before tree leaf-out. Fertile neutral to slightly acidic soil with adequate moisture is needed and then light shade during the summer months. Spreading of the root slowly establishes more plants and division of the root is best for transplants as seeds are hard to start and new plants do not flower for 3 to 4 years.
Names: The genus name, Caulophyllum, is taken from two Greek words - caulos for 'stem' and phyllos for leaf', together referring the leaf being attached right at the top of the stem. The species name, thalictroides, means 'like thalictroides' and refers to the resemblance of the leaves to the Meadow Rue, Thalictrum dioicum. Also, the common name of Cohosh comes from the Algonquin word that means 'rough', which is a description of the texture of the root. The other common names of Papoose-root and Squaw-root are probably derived from folk medicine where a decoction of the root was said to greatly relieve the pains of childbirth. The accepted author name of the plant classification, (revising the original of Linnaeus), ‘Michx.’ refers to Andre Michaux (1746-1802), French botanist who made many exploring expeditions in the U.S. collecting and cataloging many species. His notes were later used by his son, Francois, who with Thomas Nuttall published the multi-volume North American Sylva.
Uses: See notes below for lore. The plant is not grown for flowers as they are small and not colorful but rather for the foliage and the colorful berries. White-tailed deer and other browsers tend to avoid the plant due to the bitter taste of the foliage.
Above: The inflorescence. Drawing from 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. In the drawing note the representation of a flowering stem with two leaves, each leaf branched into 3 sections and each section having 3 subsections of 3 leaflets, thus 9 leaflets per each of the 3 leaf sections.
Above: 1st photo - The pale flowers of early spring. 2nd photo - Well developed fruit of August.
Below: 1st photo - The unusual way the stem twists on an emerging plant. 2nd photo - The full height stems with unfolding leaves somewhat resemble the peony plant at this stage. Note the tight flower bud cluster already formed.
Below: 1st photo - Blue Cohosh flowers in mid-April to early May - all together no more than 1/2 inch wide. The small petals appear at the base of the much longer sepals and in front of the petals are the stamens - all 3 parts in a row. 2nd photo - A pleasant sight on an early spring walk is to find these blue berries from last autumn in contrast to the brown background. Photo April 3, 2009.
Above: One 3-leaflet subsection of a leaf section. Note the venation pattern. Below: Description of the compound leaf which totals 27 leaflets when fully developed.
Notes: After introducing Blue Cohosh to the Garden in Sept., 1909 with a plant obtained in what is now Minnehaha Park, Eloise Butler added another on April 18, 1910 from the same source and 3 on May 22, 1912 from Mound MN. This plant was listed on Martha Crone's 1951 inventory of plants in the Garden at that time. She noted in her log of planting it in 1935 and 1936. The 1935 planting is interesting as the plants were delivered to the Garden by Gertrude Cram and the two were robbed shortly thereafter. Curator Susan Wilkins added more plants in 2009, '12 and '13.
Blue Cohosh is native to most of the wooded counties in Minnesota thus excluding the far NW and the tilled counties of the very south and the far SW. It is the only species of Caulophyllum found in Minnesota. In North America the plant is found in the eastern half of the U.S. except the Gulf Coast states and in Canada it is known in Manitoba, Ontario, Quebec, Nova Scotia and New Brunswick. Blue Cohosh is in the same family (Berberidaceae) as Mayapple (Podophyllum peltatum) and Twinleaf (Jeffersonia diphylla).
Medicinal lore: There is a fair amount of information in the references about this plant. The medicinal part is the root which is a rhizome which contains alkaloids and saponins. The autumn berries however, can be roasted and boiled in water, giving a decoction that resembles coffee. The root can be boiled to make a decoction or dried and then finely powdered to mix with alcohol to make a tincture. It is said to be successfully used to treat rheumatism, dropsy, epilepsy, hysteria and uterine inflammation. Native uses also are reported for the relief of cramps in menstrual periods and to relieve pain in childbirth. Blue Cohosh is also mentioned as ingredient in a number of other medicinal preparations. In Minnesota, Densmore recorded usage among the Chippewa for lung trouble and cramps and the flowers made a particularly effective treatment for burns. At the time of her research (published 1922-23) the plant was listed in the National Formulary. See Densmore (Ref. #5), Grieve (Ref. #7) and Hutchins (Ref. #12) for more information.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"