Using botanic gardens and arboreta to help identify urban trees for the future

Diversification of urban forests is essential to enhance their resilience to future biotic threats as well as those posed by a changing climate. Arboreta and botanic gardens host a wide range of plant material that can be evaluated to inform tree selection policy. This study demonstrates that plant functional traits, such as the water potential at leaf turgor loss, can be highly instructive when developing evidence‐based recommendations for urban environments. However, if botanic collections are to fulfill a critical role in understanding plant response to environment, they should not be managed solely as visitor attractions but must have scientific objectives at the forefront of management policy. Societal Impact Statement Diversification of urban forests is essential to enhance their resilience to future biotic threats as well as those posed by a changing climate. Arboreta and botanic gardens host a wide range of plant material that can be evaluated to inform tree selection policy. This study demonstrates that plant functional traits, such as the water potential at leaf turgor loss, can be highly instructive when developing evidence‐based recommendations for urban environments. However, if botanic collections are to fulfil a critical role in understanding plant response to environment, they should not be managed solely as visitor attractions but must have scientific objectives at the forefront of management policy. Summary Arboreta and botanic gardens host a multitude of species that can be utilized in research focused on improving diversity within urban forests. Higher tree species diversity will enhance the resilience of urban forests to abiotic and biotic threats and help deliver strategies that foster sustainable communities. Consequently, this study aims to demonstrate the value of botanic collections as a resource for research into tree species selection for more resilient urban landscapes. As water stress is a major constraint for trees in urban environments, understanding the drought tolerance of species is essential for urban tree selection. This study evaluates a key functional trait relating to drought tolerance. Using vapor pressure osmometry, the water potential at leaf turgor loss was evaluated for 96 species using plant material from seven botanic collections in North America and Europe. Leaf turgor loss contrasted widely in the temperate deciduous trees evaluated and, in summer, ranged from −1.7 MPa to −3.9 MPa. Significant differences in