Variation in survival and growth of cuttings in two clonal propagation methods for hybrid aspen (Populus tremula×P. tremuloides)

Cloning hybrid aspen (Populus tremula L.×P. tremuloides Michx.) in vitro is costly. Inexpensive propagation methods for the species are needed. Two cloning methods and 10 clones of hybrid aspen were tested in a greenhouse environment. In the stock plant method greenwood cuttings were obtained from the same stock plants at 4 weeks intervals. In the successive method cuttings were taken from newly rooted cuttings and the cut stems were grown as normal saplings. The stock plant method produced new cuttings distinctly faster than the successive method. Significant differences among the clones were found in terms of growth and ability to produce new, vigorous cuttings. Except for the initiation of stock plants, which were obtained from micropropagation, all of the cloning was done in an air-conditioned growing room at low light intensities. Both of the methods can be successfully applied for propagating greenwood cuttings of hybrid aspen. The ability of different clones to be multiplied varies so much that selection of the best clones for production is essential.