Actaea racemosa Seeds | Black Cohosh
LATIN NAME: Actaea racemosa
COMMON NAME: Black Cohosh, Black Bugbane
Plant Profile
Black cohosh is a woodland perennial that looks like a white wand stuck into the shade. It grows one to two and a half metres from a thick, knotty rhizome, with large, twice- or thrice-divided leaves and a single upright stem that carries a long, narrow raceme of small white flowers, thirty to sixty centimetres of it, from early summer into autumn.
The flowers have no petals worth mentioning, just a mass of white stamens that gives the spike its bottlebrush look, and the whole plant smells faintly unpleasant, which is the origin of the name bugbane. The foliage is handsome in a bold, dark way and stays good until the first frost. In the wild it grows in rich, moist deciduous woodland from New England south to Georgia and west to Missouri, often on slopes and in coves where the soil stays cool.
Science & Biotechnology
The rhizome is one of the most studied plant medicines in the world. It contains triterpene glycosides, chiefly actein and 27-deoxyactein, together with cimicifugoside and aromatic acids, and extracts standardised to those compounds have been tested in dozens of clinical trials for menopausal hot flushes, with results that are modest and inconsistent but sufficient to keep the product on the market.
Safety is the other half of the story. A small number of cases of liver injury have been reported in association with black cohosh products, and several regulators require a warning label; the mechanism is not established, and some cases have been traced to misidentified material or to contamination with other species. The plant should not be used in pregnancy, and anyone with liver disease should avoid it. In the garden it is pollinated by flies and beetles attracted to the smell, and it is self-fertile.
Uses & Benefits
Black cohosh is grown as an ornamental for shady borders, woodland gardens and the back of a damp bed, where its height and its late-summer wands are useful at a season when shade perennials are thinning out. It is a good companion for ferns, hostas and rodgersias, and it holds its shape without staking if the site is sheltered. The dried flower heads last well and can be used in arrangements.
The medicinal use is the reason most people know the name, and it should be treated as a medicine rather than a garden herb: standardised extracts are the form that has been studied, the raw rhizome is not equivalent, and the liver question means that casual self-treatment is unwise. The related Asian species are used differently in Chinese practice, and the two traditions should not be conflated.
Growing from Seed
The seed is doubly dormant, needing a warm, moist period followed by a long cold one. Sow fresh seed in autumn in a moist, humus-rich mix and leave the pot outdoors for two winters, or give three months at twenty degrees followed by three at four degrees. Germination is slow and can take a year.
Grow the seedlings in shade, in soil that stays moist but drains, and plant out when the rhizome is thick enough to handle. Space plants seventy centimetres apart, because the clumps widen slowly into substantial colonies. Mulch with leaf mould every autumn and do not let the ground dry out in summer; the plant resents drought more than cold, and it will sulk for a season after a dry spring.
Our Take
A bold shade perennial first and a controversial medicine second; grow it for the wands, not the pharmacy. Moist shade and leaf mould are all it needs to make its wands.
Related Reading
Gardeners who grow Black Cohosh often pair it with these related subjects: