Acclimation, the ability of an organism to modify its physiology, anatomy, or morphology in response to environmental stimuli, is a cornerstone of tree adaptation and survival in dynamic environments. Understanding the mechanisms behind acclimation is critical to addressing today’s pressing ecological and environmental challenges, including habitat loss, biodiversity conservation, and the impacts of climate change. In particular, drought and heat stress are increasingly urgent research targets due to their rising prevalence and intensity under ongoing global warming. Arboreta, specialized botanical, multi-species collections of trees, shrubs, and other woody plants, offer unique opportunities to study stress acclimation in semi-natural settings. These living laboratories provide invaluable data for understanding species-specific responses to climate stressors outside natural climatic optima, simulating effects of predicted future climatic scenarios and exploring long-term adaptive strategies. This paper highlights how arboreta contribute to advancing knowledge of climate acclimation in trees and shrubs and discusses their broader implications for ecology, conservation, and climate resilience. Furthermore, it underscores the need for enhanced coordination and standardization among arboreta worldwide to optimize their potential as critical research platforms and improve global conservation strategies. However, current research is hampered by the limitations of field and laboratory studies, which often struggle to isolate specific environmental drivers or replicate long-term ecological dynamics, and by the lack of coordination and standardized protocols among arboreta.