| Abstract: | Autumn frost hardiness of offspring from clones (originating from 66.0–68.8° N) in six southern (62° N) and one northern (66.5° N) Pinus sylvestris seed orchards in Finland, was evaluated. One‐year‐old seedlings derived from open pollinated grafts of young, intermediate, and fairly mature age, and natural stand seedlings, were artificially freeze tested. The northerly located orchard produced the least injured offspring. There were no significant systematic differences between age classes. Neither were there any indications of decreased freezing injury with later age classes. The family variance was significant in four orchards. The estimated injury levels of orchard offspring were, in general, closer to those of natural stands in the neighbourhood of the orchard than natural stands at the place of clonal origin. It is suggested that not only differences in mother clone hardiness but also clonal differences in pollen contamination rate caused the observed family variation. |
