Although the genetic aspects of biological invasions are receiving more attention in the scientific literature, analyses of phenotypic plasticity and genotype-by-environment interactions are still seldom considered in tree invasion biology. Previous studies have shown that invasions of tree species can be affected by intraspecific phenotypic plasticity, pre-adaptation, and post-introduction evolution, and we suggest there are opportunities for new developments in this field. Here, we present a description of the use of quantitative and molecular genetics in tree invasion biology, and propose an approach based on common garden experiments, quantitative and molecular genetic methods to investigate the role of adaptive evolution, phenotypic plasticity, and genotype-by-environment interactions in tree invasions, particularly at the infraspecific level. We illustrate the utility of this approach using examples from quantitative genetic studies of Pinus and an example from a classical reciprocal common garden experiment with Acer species. By using this approach, researchers can test hypotheses about the role and strength of genetic and environmental effects on population-level invasiveness and gain insights into evolutionary processes that occur during biological invasions. Moreover, knowledge of phenotypic plasticity and local adaption of tree populations may help researchers improve assessments of invasion risk.