Alleviation of seed dormancy in white spruce (Picea glauca [Moench.] Voss.) is dependent on the degree of seed hydration

White spruce (Picea glauca [Moench.] Voss.) seeds were moist chilled at 5 °C in the dark under seven different regimes which altered the degree of seed hydration, and/or the presence and type of water containing media in contact with the seeds. Seeds that had been exposed to the regimes for 0, 1, 2, 3, 4, 5, 8, and 12 weeks were tested for germination percentage, mean germination time, and germination uniformity under alternating 20/30 °C temperatures for 16 and 8 h, respectively. Seed from dormant seedlots had a lower percentage germination, and completed germination more slowly, and less uniformly if dormancy was not first alleviated. Moist chilling of any duration did not alleviate dormancy at or below 20% moisture content fresh weight (MCFW). In contrast, at MC's of 25% and greater, germination percentage was maximal after just one week of moist chilling, although the speed of germination benefited by an additional one to two weeks of moist chilling. The coefficient of uniformity of germination was maximal within two weeks of the commencement of moist chilling when it was affected by treatment. The type of treatment used influenced the stability of all three germination parameters over time. Moist chilling (stratification) between layers of 1:1 v/v moist sand/Perlite consistently had detrimental effects on all parameters, for all seedlots, as the duration of treatment progressed beyond four-five weeks. Some seedlots were more susceptible to death during treatment than others. Susceptible seedlots tended to survive moist chilling for longer periods at MC's at or below 20% FW. The abrupt change in the efficacy of moist chilling in alleviating dormancy around 25% MCFW was associated with the boundary between water binding regions 3 and 4 based on sorption/desorption isotherms for both white and sitka spruce. The best overall treatments were soaking seeds for 24 h in water prior to surface drying, and then moist chilling them in polyethylene bags (final MC ~25% FW), and moist chilling at uncontrolled MC in Petawawa germination boxes.