Effect of planting depth, planting season, and fungicide treatment on establishment of black cohosh in a poorly drained soil

Black cohosh [Actaea racemosa L., Cimicifuga racemosa L. (Nutt)] is a perennial herb commonly used for treatment of menopausal symptoms in humans. The increasing demand for this plant is leading to serious over-harvesting from the wild and presents an opportunity for potentially profitable cultivation. The plant produces a large rhizome, the principal medicinal organ, which appears to be especially sensitive to heavy soil, and prone to fungal attack if soil water drainage is not adequate. After an earlier crop failure (attributed to a Phytophthora-Pythium disease complex) in an established black cohosh nursery bed, two experiments were conducted in the same soil to determine if certain horticultural approaches could help to avert fungal infection under less-than-ideal conditions. Treatments included single postplanting applications of the fungicide mefenoxam, transplantation in fall versus spring, and shallow (0.5 cm) versus deep (6.5 cm) placement of rhizomes. Shallow placement significantly improved long-term rhizome survival, but was still not able to compensate adequately for a poorly-drained soil. The horticultural approaches we studied do not appear to be reliable alternatives to proper site selection in the cultivation of black cohosh.