Stress tolerance and horticultural evaluation of the genus Salix

The objectives of this study were to investigate the adaptability of the genus Salix to stressful conditions and to promulgate its ornamental potential. This research has focused on Salix's tolerance of natural and anthropogenic stresses, including flooded soils, soil compaction, heavy metals, and ozone pollution; all are common conditions in urban environments. I found that neither soil compaction nor flooding caused a significant reduction in the growth of willows, but that anaerobic conditions rapidly triggered a wide range of morphological adaptations. The copper and cadmium uptake study, conducted in a greenhouse hydroponic system, revealed a general tolerance of willows of increased metal in the solution and the translocation of metal into plant aerial organs; copper appears to be more toxic to plants and less mobile than cadmium. The response of Salix species to acute ozone exposure was studied in a fumigation chamber and it revealed marked interspecific differences; both ozone-sensitive and ozone-tolerant species were documented. The ornamental qualities of cut branches from twenty species and cultivars of shrubby willows were evaluated and described in detail, focusing on those attributes, and phenological sequence, important for the floral industry. More than fifty promising willow species for alpine and small urban gardens were selected based on multi-year observations. Their names were taxonomically verified, and they are presented with detailed descriptions, horticultural uses and requirements, and details of provenance.