Effect of shade, fertiliser and irrigation on the production of goldenseal (Hydrastis canadensis L.)

Goldenseal (Hydrastis canadensis L.; Ranunculaceae) is a North American perennial, woodland herb with roots and rhizomes that demand high prices as herbal medicines. Harvesting this species from wild populations has endangered its existence and greater effort is now being directed at growing it in managed stands. Two trials were conducted to investigate the effects of shade, fertiliser and irrigation on plant production. Goldenseal growth in full light was compared with that under 32, 57 and 84 % shade. Growth in the first year was best under 57 % shade, but in the second year higher growth was achieved under 84 % shade. In the second trial, fertiliser and irrigation treatments were applied to a goldenseal crop established in the previous year and grown for a further four years before harvest. Additional water increased the goldenseal root and rhizome production by 311 %. Fertiliser application had no beneficial effect on rhizome production and had little effect on the nutrient content of the roots and rhizomes. Calculation of the nutrients removed by harvesting a four-year­ old crop of 2000 kg/ha showed that the amount of fertiliser needed on an annual basis to replace these losses was low.