The effectiveness of foliar auxin application to stock plants in rooting of stem cuttings of ornamental shrubs

Experiments conducted at commercial nurseries near Warsaw, Poland compared the effectiveness of foliar auxin application relative to the traditional use of rooting powders inducing rhizogenesis in the cuttings of several species of ornamental shrubs. Stock plants were sprayed with NAA or EBA in concentrations of 50-1000 mg center dot dm(-3), 24 hour prior to cuttings' harvest. Commercial rooting powders were Rhizopone AA and Ukorzeniacz AB, containing IBA and NAA, respectively. The degree of rooting and the percentage of rooting were evaluated. Root formation depended on the species tested, the auxin used and its concentration as well as on the method of hormone application. Generally, spraying stock plants with IBA or NAA in the range of concentrations of 50-500 mg center dot dm(-1) was the effective way of auxin application in ornamental shrub propagation comparable to the traditional use of rooting powders. Therefore it can be recommended for nurseries.