Eucalyptus is a highly diverse tree genus and selected species are the most sought after hardwood plantation species worldwide. Each of these ecologically as well as commercially important species have a wide ranging natural habitat and large associated intra-specific genetic diversity. However, the plasticity of their genetic diversity to respond to future climates is largely unknown. Yet, this information is crucial in forward planning of ecosystem management and financial gain. Our research is addressing the role of genotypic (G) diversity in provenances of E. grandis to adjusting to their environment (E). Particularly, the interaction G × E, represented by elevated concentrations of atmospheric CO2 (eCO2) and water availability is assessed. We found that trees originating from colder climates produced larger biomass than trees coming from warmer climates when supplied with sufficient water. Furthermore, even though photosynthetic rates (A) increased in all provenances in eCO2 under well-watered conditions, trees from colder climates exhibited greater plasticity when water was limited. They showed greater increase in A under eCO2 compared to rates of A under ambient CO2. Our research highlights the importance of exploiting intra-specific variation in Eucalyptus to optimize tree growth under forecasted climatic conditions. Our results demonstrate that provenances of E. grandis originating from colder climates appear to be more suited in coping with future climate challenges like eCO2 and water limitation.