Abstract

Studies were conducted to investigate the severity of cutting back stock plants on adventitious rooting of layered stems and stem cuttings of Quercus bicolor Willd. (swamp white oak) and Quercus macrocarpa Michx. (bur oak). Rooting averaged 77% in Q. bicolor and 70% in Q. macrocarpa layered stems from the cutback stock plant group, compared to air layered stems from intact plants which averaged 1% in Q. bicolor and 0% in Q. macrocarpa. In another experiment cuttings were taken from three stock plant heights [4 cm (1.6 in), or 100 cm (39.4 in) stumps and intact plants ∼ 170 cm (66.9 in)] which were either etiolated or grown in natural light and rooted under mist. The best rooting (59%) and average number of roots (9.3) were found in etiolated Q. bicolor cuttings taken from 4 cm (1.6 in) stumps. Q. macrocarpa cuttings rooted poorly with only 7% of the cuttings rooting. By taking cuttings a week earlier for rooting (2 weeks, at the softwood stage), rooting in Q. macrocarpa was possible, with the best rooting (46%) found in etiolated cuttings taken from 4 cm (1.6 in) stumps. Overall, the highest rooting and greatest number of roots occurred in etiolated layers and cuttings from the 4 cm cutback group. Rooting generally increased with increasing extent of stock plant cutback