Root wrenching may influence dormancy development of Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings in the nursery.

Abstract

The influence of root wrenching on the dormancy and cold hardiness development of Queen Charlotte Island (QCI) provenance of Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings was investigated. The root wrenching treatment was carried out in mid September, 1991, with the objective of inducing early dormancy to facilitate early lifting of stock for field planting. Wrenching delayed bud development, lowered root mitotic activity, and reduced cold hardiness levels during dormancy development, compared with the unwrenched seedlings. The rate of root mitotic activity and cold hardiness deacclimation in the spring was also slowed by the wrenching treatment. Although late season root wrenching had the opposite effect to that envisaged, it may be possible to extend the lifting season by two to three weeks using this treatment, as dormancy release was also delayed.