Use of Solarization to Kill the Root Crown and Reduce the Seed Bank Viability of Rubus armeniacus Focke and Cytisus scoparius (L.) Link

Abstract

Himalayan blackberry (Rubus armeniacus Focke) and Scotch broom (Cytisus scoparius (L.) Link) are two common invasive species of the Pacific Northwest. While many methods currently exist to control these two species, both posses inherent characteristics and structures making them resistant to existent methods in the forms of aggressive vegetative growth and resprouting from root fragments and large persistent seed banks. The goal of this thesis is to explore the potential application of solarization as a control method for these two species. In a field trial, the effectiveness of solarization was to tested against several existent control methods focusing on the stem and root crown survivorship. In a subsequent greenhouse experiment, the seed banks of R. armeniacus and C. scoparius were subjected to solarization at varying soil temperatures. Results indicate that solarization does have the potential of killing root crowns and reducing the seed banks of R. armeniacus and C. scoparius. Clear plastic solarization was found to be more effective at increasing the soil temperature than black plastic and increases in soil temperature resulted in reduced root crown, stem, and seed bank survival. Further research in to solarization though will be required to best modify the technique to match the climate of the Pacific Northwest.