Provenance effects on pre-germination treatments for Eucalyptus regnans and E. delegatensis seed

The effects of seed size, and of chilling and smoking pre-treatments on germination of commercial Eucalyptus regnans and Eucalyptus delegatensis seedlots selected from provenances at various altitudes were investigated. Seed viability was relatively high in E. regnans compared to that of E. delegatensis. Large E. regnans seed germinated at a faster rate than small seed, but there was no difference between E. delegatensis seed sizes. Chilling imbibed seed for 1 week at 4 °C increased germination rate in the higher altitude E. regnans seedlot but had no effect on seed from the lower altitude. Chilling for 1 and 3 weeks increased germination rate and percent in all E. delegatensis seedlots, with the greatest response being observed in seed from the highest altitude. Exposing seed to smoke had no effect on germination of either E. regnans or E. delegatensis.

The results indicate that concerns over low germination rates in commercial E. regnans seedlots may be unfounded in some seedlots and the species could be successfully incorporated into commercial tree nursery operations without substantially altering management practices. However, for E. delegatensis improved seed cleaning and chilling imbibed seed for 3 weeks prior to sowing may be required to improve germination rate and percentage.