Location of cones in the crown and along shoots of Sitka spruce (Picea sitchensis (Bong.) Carr.) and the influence of coning intensity and shoot size

Abstract

The location of female cones in the crowns of rooted cuttings and mature forest-grown trees of Sitka spruce (Picea sitchensis (Bong.) Carr.) was recorded. When cones were allocated to crown sections there were clear patterns of bearing, with the majority of cones on second-order distal shoots on whorls 2 and 3. As total cone production increased, the bearing zone progressed onto more proximal shoots on upper whorls and distal shoots on lower whorls. On individual branches of clonal grafts, female cones tended to be borne on more distal shoots than male cones. Female cones, on all sample sets, tended to be borne primarily on second-order shoots and male cones, on the clonal grafts, on third-order shoots. On the clonal grafts there was a weak, though significant, relationship between the number of original buds and female, but not male, cones on a shoot. Cones were also described by position on bearing shoots. There was a tendency for the proportion of progressively more proximal cone positions to increase on lower-order shoots and vice versa. Cone position was also influenced by the dimensions of the bearing shoot independent of its position with a distal shift in cone-bearing position as shoot dimensions decreased.