Root and rhizome production of goldenseal ( Hydrastis canadensis L.) under cultivated conditions in New Zealand.

Root and rhizome production of goldenseal (Hydrastis canadensis)was measured annually from 1996 to 2002 under shade in Waikato, New Zealand. Root and rhizome production increased annually to 60–70 g dry matter (DM)/plant after 6 years, giving a root:rhizome DM yield of 5500 kg/ha. Initial growth was dominated by the roots but by the fifth and sixth year, the root:rhizome ratio remained constant at 1.2. After 6 years, approximately 84% of the root and rhizome mass was in the first 50 mm of soil, with very few roots below 100 mm. The berberine concentration in the roots and rhizomes was always above theUS Pharmacopeia's quality threshold of 2.5%. The hydrastine content was only above the US quality threshold of 2% in the rhizomes and in the roots in 1999. In the 2001 and 2002 analyses, hydrastine concentrations dropped markedly in both roots and rhizomes with the hydrastine levels in the roots being below the quality threshold. [ABSTRACT FROM PUBLISHER]