Vegetative Propagation of Five Northern Forest Understory Plant Species from Either Rhizome or Stem Sections

Five understory plants, Asarum canadense L., Caulophyllum thalictroides (L.) Michx., Sanguinaria canadensis L., Trillium grandiflorum (Michx.) Salisb., of the Northeastern hardwood forests, and Oplopanax horridus (Sm.) Miq., of Western North American temperate forests, are of particular interest for horticultural and natural medicinal products industries. A rapid and efficient propagation method was needed to reproduce these plants vegetatively. To achieve this, the effect of 1000 mg·L−1 (for herbaceous species) or 3000 mg·L−1 (for O. horridus) auxin (IBA) and/or cytokinin (kinetin) on the growth of rhizome (for A. canadense, C. thalictroides, S. canadensis, T. grandiflorum) or stem sections (for O. horridus) was investigated. Nontreated controls were included for each species and an additional control with an intact apical bud was included for A. canadense, S. canadensis, and T. grandiflorum. No vegetative propagation was obtained for T. grandiflorum. Survival of O. horridus and C. thalictroides propagating units was 60% to 80% and 90% to 100%, respectively, and both rooted well even in absence of growth regulators. Asarum canadense produced two times and S. canadensis three to four times more roots when treated with the IBA + kinetin or the IBA treatment, respectively, compared with the control rhizome sections without an apical bud. For these two species, the presence of an apical bud enhanced survival and/or shoot emergence and those rhizome sections produced on average more biomass than the other treatments. Our results showed that either rhizome or stem sections can provide an efficient method to propagate A. canadense, C. thalictroides, O. horridus, and S. canadensis and thus reduce pressure on wild populations.