A comparison of hedging and repeated cutting cycles for propagating clones of Sitka spruce

Abstract

Hedging and serial propagation are two options for providing plant material for the long‐term propagation of conifer clones. This study compared both options using eight half‐sibling clones of Sitka spruce which were propagated for 18 years. The four treatments were propagation from the original plant (ortet), hedges from cuttings (ramets) of the first and second propagation cycles, and serial propagation from ramets of the most recent propagation cycle. Both rooting success and performance in a field experiment were compared. The best overall rooting was obtained from serial propagation from the previous cycle; and the poorest rooting was from cuttings from the original ortet. Rooting success was generally good from 1978 to 1994 (up to 18 years from seed) for serial propagation, but only up to 11 years for hedges. There were some differences between clones for rooting success, but the results were not consistent. In the field, there were no consistent differences in survival or height growth between propagation treatments over time. There was no evidence of any decline in vigour after 6 years' growth in the field for treatments planted out between 1982 and 1992 (i.e. between 4 and 14 years of age). There were some differences in stem form shortly after planting, with cuttings from serial propagation being more upright. However, such differences did not persist, with all treatments showing an upright pattern of growth within a few years of planting. The propagation success is encouraging for a clonal forestry strategy with Sitka spruce. The best long‐term option may be to use hedges for bulk propagation and replace them regularly by serial propagation. The results are discussed in relation to current thinking about maturation effects on rooting and subsequent early growth of cuttings in conifers.