Choosing Sitka spruce planting stock

Over 90% of the Sitka spruce planted in Britain today is from ‘improved’ planting stock, which is predicted to produce around 25% more timber at final rotation, compared with material imported from the Pacific North West. Forest managers have a choice of improved stock: seedlings raised from seed collected in orchards established around 25 years ago, or rooted cuttings taken from stock plants raised in nurseries using controlled pollinated seed produced by tree breeders. Although the predicted gains in growth rate often appear similar, the predicted gains for quality traits are usually superior for the rooted cutting stock. The down side is that the rooted cuttings are usually more expensive due to the extra production costs at the nursery. Which planting stock gives the best financial return in the long run is dependent on a number of variables. This Practice Note provides guidance to forest managers on how to choose the most appropriate planting stock, depending on thinning regime, rotation length, growth rate, and economic factors such as the premium paid for rooted cutting stock at the time of planting and the likely premium for green logs at harvest.