Actaea racemosa L.

Black Cohosh

Actaea racemosa plant

Family - Ranunculaceae

Habit - Rhizomatous perennial forb, sometimes with woody base.

Stems - Flowering stems to +2m tall, erect, glabrous, glaucous, from a woody caudex, herbaceous, green but purple at the nodes.

Actaea racemosa nodePurple node.

Leaves - Basal and alternate, petiolate, glabrous, to 1m broad, -1m long, ternately divided, purple at the joints. Ultimate leaflets serrate, green adaxially, silvery-green abaxially, with a few hairs abaxially on the veins. Serrations of margin with a lighter green or yellowish apex. Veins of leaflets impressed adaxially. Leaves of the flowering stem reduced to bracts.

Actaea racemosa leafLeaf.

Inflorescence - Terminal and axillary racemes to +/-50cm long. Axis of the inflorescence tomentoulose. Pedicels to 6cm long in flower, slightly longer in fruit, whitish tomentose. Each pedicel subtended by a minute bract. Bracts attenuate, 1-3mm long.

Actaea racemosa inflorescenceInflorescence

Actaea racemosa inflorescenceInflorescence

Flowers - Apetalous, Asepalous, fetid. Stamens many, +/-100. Filaments white, filiform, glabrous, to 5mm long. Anthers white, 1mm long. Ovary superior, white, tomentose, obliquely ovoid, 2.5mm long in flower, unilocular, with +/-10 ovules. Style wanting, forming a slight beak in fruit.

Actaea racemosa flowerIndividual flower.

Fruits - Follicles, 1 per flower stalk, 5-10 mm long, ovoid or ellipsoid. Seeds semicircular, smooth or ridged.

Flowering - May - August.

Habitat - Low rocky woods, base of bluffs.

Origin - Native to U.S.

Other info. - This distinctive species can be found across much of the southern third of Missouri, and eastward from Missouri into the northeast and Canada. When in bloom, the plant is easy to ID in the field because of its big leaves and long inflorescences. The plant also has a foul odor, especially when in flower.

This species has a long tradition of medicinal use by Native Americans, and more recently for women's health purposes including treatment of symptoms of menopause, premenstrual syndrome (PMS), painful menstruation, acne, osteoporosis, and for inducing labor. The plant may also have anti-inflammatory properties. However, controlled clinical trials have thus far failed to show a consistent benefit. The plant contains a large number of compounds having potential physiological activity, and these can occur in widely varying amounts and proportions. It is certainly possible that further research will reveal useful medicinal properties of the plant or one or more of its chemical constituents. The plant is considered toxic, so any use as a medicinal herb must be based on a solid understanding of the appropriate dosage and awareness of the potential risks.

Photographs taken at the Current River Conservation Area, Reynolds County, MO., 6-26-01, and at Big Spring Park, MO., 7-1-03 (DETenaglia); also at Johnson's Shut-Ins, Reynolds County, MO, 6-26-2015 (SRTurner).