The Umeå Aspen (UmAsp) collection is a population of aspen trees (Populus tremula) from around the Umeå kommun, collected and cloned into two contrasting common gardens: one site closer to the coast at Skogforsk in Sävar and one at the inland, higher elevation site at Kulbäcksliden near Vindeln. Aspen is a model species for forest tree genetics and has high value in forest ecosystems. The purpose of the collection is to study natural genetic variation in traits including physiology, phenology, growth and biotic interactions. We have DNA sequencing data for all UmAsp individuals to enable population genetics studies, and together with phenotype data we are conducting genome-wide association mapping to identify and genetic variants associated with each phenotype. The two gardens facilitate validation of our findings in different environments and examination of genotype-by-environment interactions of the phenotypes studied. Principal Investigator: Stefan Jansson. Field trials manager: Kathryn Robinson.