Wildflower of the Year 2017 Black Cohosh (Actaea racemosa)

The slender wands of flowering Common Black Cohosh beckon us to explore woodlands.

Photo by Richard Stromberg

Common Black Cohosh is a perennial rhizomatous forest herb. Its horizontal rhizomes bear numerous adventitious roots on the underside and aerial stems of annual duration on the upper side, along with knobby scars left from aerial stems of previous years. Leaves are alternate, twice or thrice compound in ternate or pinnate patterns, and large — up to a meter in length. Individual leaflet size and shape vary with position in the large compound leaves, with position of a leaf on the stem, and from population to population. Most often leaflets are coarsely serrate, lobed to deeply incised, with a truncate to cuneate base and an acute to acuminate apex and range 3-10 cm in width and 2–10 cm in length.

Drawing by Nicky Staunton

Inflorescences are terminal, held well above the leaves, sparsely branched, and up to about 1 m long, resulting in a total height of robust flowering specimens to 2 m or so; flowering commences at the bottom of each raceme and progresses apically. The white flowers possess 4 or 5 concave sepals about 5 mm long that promptly drop at anthesis. Just above the position occupied by sepals one finds a series of organs that can be interpreted either as petals or staminodes (sterile stamens); these are oblanceolate to oblong, about 3 mm long, and bear a pair of somewhat irregular lobes at the apex. Functional (fertile) stamens are numerous, ranging 55–100 per flower, and form a globelike mass roughly 2.5 cm in diameter; stamens are 8–10 mm wide and each consists of a slender filament supporting two anther sacs of pollen. Usually there is just a single pistil at the center of the flower but, rarely, 2 or 3 may be present. Ovaries are stout and barrel-shaped, arising from a short stipe at the base and capped with a short style and flat stigma. Fruits are dry follicles, 6–9 cm long. During fruit development stigmas become displaced laterally, and transversely oriented veins of the ovary wall become prominent. Seeds are semicircular, with minutely roughened sides, about 2 mm long and are produced in a double row inside the follicle.

Photo by W. John Hayden

Name and Relationships

Black Cohosh is a member of Ranunculaceae, the Buttercup Family. Linnaeus published the name Actaea racemosa in his monumental work Species Plantarum (1753). Actaea is the ancient Greek name for Elderberry, but why Linnaeus might have applied that name to this plant is difficult to fathom; racemosa refers to its elongate inflorescence. In 1818 Thomas Nuttall transferred this species to Cimici­fuga, forming the combination Cimicifuga racemosa, the name by which Black Cohosh was known for many years. Insight from cladistic analysis of gene-sequence data has led to reinstatement of Black Cohosh in Actaea, along with several other species once classified in Cimicifuga. Black Cohosh is understood to be closely related to Actaea pachypoda, White Baneberry or Dolls’-eyes. As now interpreted, the genus Actaea contains about 28 species found throughout temperate regions of the northern hemisphere.

Human Uses

Drawing by Nicky Staunton

Native Americans used Black Cohosh for a variety of medicinal purposes, and some of these uses continue to this day. The plant is reputed to possess analgesic, sedative, and anti-inflammatory effects. Further, there are commercially available dietary supplements used by some to treat a variety of gynecological conditions. The VNPS makes no endorsement for (or against) the use of Black Cohosh for medical purposes.

In the Wild

Black Cohosh is a plant of mesic to dry forests, thriving in soils rich in base elements. Flowers emit a sweet/fetid odor that attracts flies, gnats, beetles, and bumblebees, its presumed pollinators; nectar and pollen constitute pollinator rewards. Black Cohosh is larval host for the Appalachian Azure butterfly (Celastrina neglectamajor).

In the Garden

Cultivation of Black Cohosh is easy if appropriate garden requirements of light shade, rich soil, and sufficient moisture are met; it is prized for its graceful midsummer blooms. Plants can be propagated by seed or rhizome division. To germinate, seeds require exposure first to warm temperatures followed by cold; sowing outdoors as soon as ripe seed are available should yield good germination, but it may take years before plants attain flowering size. Variety dissecta, with deeply cut leaflets, and var. cordifolia, which has shallowly lobed leaflets resembling maple leaves, are available in the nursery trade. In addition, a number of cultivars have varying degrees of purple (anthocyanin) pigmentation.

Where to See It

Black Cohosh is found throughout Virginia except in the outer Coastal Plain. It is most frequent in the mountains, becoming progressively less common through the Piedmont and inner Coastal Plain. Further, Black Cohosh is widely distributed in eastern North America, from western Massachusetts to Missouri and south to Tennessee and Georgia.

Conservation Status

Black Cohosh

The conservation status of Actaea racemosa is secure, but as with all native plants, populations are subject to habitat alteration.

Gardeners should not collect Black Cohosh in the wild and should be certain that all native plants purchased for home gardens have been nursery-propagated, not wild-collected.

For a list of retail sources of nursery-propagated plants and responsibly collected seeds, check out our list of Regional Native Plant Nurseries, or send a stamped, self-addressed envelope to the Virginia Native Plant Society, Blandy Experimental Farm, 400 Blandy Farm Lane, Unit 2, Boyce, VA 22620; e-mail info@vnps.org; or call 540-837-1600.

To see and learn more about interesting species of plants native to Virginia, contact your chapter of VNPS for the times and dates of programs and wildflower walks in your area.

W. John Hayden
VNPS Botany Chair

View or download the Black Cohosh Brochure.