Development of eastern cottonwood cuttings as modified by cutting length and surface area available for rooting

Abstract

Eastern cottonwood (Populus deltoides Bartr. ex Marsh.) is commonly propagated using un-rooted cuttings. While cutting length and diameter, genetics and environmental conditions are often cited as major factors contributing to the successful establishment of cottonwood plantations, it is difficult to determine which specific cutting characteristic or mechanism leads to improved root establishment or plant development. For example, increasing stem size can affect rooting and subsequent plant growth by altering the cutting energy reserves as well as the surface area from which latent roots develop. In this study, the contribution of cutting length and belowground surface area to rooting and early growth was examined for eastern cottonwood. To discern cutting length effects, the belowground portion of four different cutting lengths was restricted so each cutting had the same belowground surface area available for rooting. To discern surface area effects, 40-cm-long cuttings were restricted to produce four different levels of surface area from which roots could develop. Leaf area, stem height, aboveground and belowground biomass, and root numbers were measured after 13 weeks of growth. The only statistically significant relationships related to biomass were due to the initial differences in cutting length. Cuttings with greater surface areas formed more lateral roots, while longer cuttings did not. By contrast, increased cutting lengths resulted in greater numbers of basal roots, but not for cuttings with greater belowground surface areas.