Size Influences on the Survival of Willow Cuttings Under Operational Field Conditions

Willows (genus <i>Salix</i>) are increasingly used in operational-scale ecosystem reclamation; however, different opinions exist regarding the optimal cutting size for planting under field conditions. We compared the survival of field-planted willow cuttings sourced from upland and lowland areas with varying diameters and lengths across two growing seasons. Cuttings were grouped into 15 size classes with different diameters (0.5, 1.0, 2.0, and 3.0 cm) and lengths (15, 30, 50, and 100 cm) and planted in groups according to their source (upland or lowland, each area potentially reflecting a different assemblage of species) within three reclaimed industrial borrow pits east of Peace River, Alberta. We considered cuttings that displayed leaf flushing as surviving individuals. Survival probability tended to be greater for larger diameter and length cuttings sourced from lowland habitats. Cutting survival was greatly reduced in year two, especially for upland-sourced cuttings. The greater survival in larger sizes we observed may be due to greater total carbohydrates available for leaf flushing and rooting. As we did not control for species composition, the higher survival of cuttings from low-lying areas may result from species-specific differences among cutting sources, reflected by compositional differences we detected among surviving individuals in year two. Our findings suggest that under field settings, cuttings with > 2.0 cm diameter by 50-100 cm length sourced from low-lying flood-prone areas may be optimal for willow establishment. Further studies should examine the role of species and population-level genetics in driving the upland versus lowland differences in observed willow-cutting survival.