A major foundation of trait-based ecology is that traits have an impact on individual performance. However, trait-growth relationships have not been extensively tested in trees, especially outside tropical ecosystems. In addition, measuring traits directly related to physiological processes (‘hard traits’) remains difficult and the differences between inter- and intraspecific relationships are seldom explored. Here, we use individual-level data on a set of hydraulic, leaf and stem traits to explore which traits are the best predictors...