provenance tests in ontario have been used for decades to evaluate the optimal seed sources for different environments. understanding the genetics, adaptations and selection pressures of tree species using provenance testing will help determine future favourable planting locations. the growth of many tree species will be adversely affected by climate change, as most woody plant species cannot keep up with the rate of change. white spruce (picea glauca (moench) voss) is a widespread, economically important tree species for the canadian forest industry. being a widely distributed species, ontario has many white spruce provenance test trials with sources from across the province and the country. provenances from across ontario have been planted at a kakabeka test site to determine the top performing seed sources. this thesis explores the variation in height between provenances at this test site to determine the climatic variables which are most significantly related to this intraspecific variation. the top performing provenances at the kakabeka site originated from southern ontario and quebec, and the worst performing provenances mostly originated from northwestern ontario. provenance and block effects explained a significant portion of variation in mean heights. growing season climate variables showed a significant relationship to height variation among provenances. the best predicting variables were mean annual solar radiation (mar) and hargreaves reference evaporation (eref). this study provides valuable data to determine the optimal seed sources for current climate conditions.