In order to investigate the difference of rootability between 15 clones of Populus alba × glandulosa selected based on the growth performance, rooting of cutting experiments with these 15 clones were conducted at the nursery for six years from 1970 to 1975. Cutting experiments in a temperature controlled incubator in which the temperature of the cutting bed were set to 10℃, 15℃, 20℃, 25℃ and 30℃ were also performed. Along with these experiments air layering experiments were performed to compare with the rootabilities obtained from nursery trial. The results obtained so far could be summarized as follows. 1. The best rooting clones were 65-22-4 and 65-22-11, and the average rooting percentages of these two clones for six years were 76.7%, and 72.9% respectively. The poorest rooting clone was 66-6-8 showing average rooting percentage of 45.8%. 2. The middle class of rooting percentage was ocuppied by the clones; 66-14-29, 66-14-93, 66-25-5 and 67-6-3, and the range of their rooting percentage was 60∼69% on average. 3. The rooting performances observed through the nursery, the incubator and the air layering experiments were almost the same with exception of few clones. 4. P. alba × glandulosa showed the best rooting percentage at the cutting bed of 20℃ 5. The most roots, i.e. 78.5% of root per cutting were developed from the bottom part of the cutting shoot. 6. Adventitious and call use roots could observe in the cuttings.