Early Survival and Growth of Climate-Ready Trees and Native Oaks in an Urban Canopy Planting Program

Abstract Background Many cities in the water-limited American West aim to expand their urban tree canopies as a strategy to address heat. For tree planting initiatives to contribute substantially to these canopy goals, selected species must have high survival and be able to withstand future climate conditions, including higher temperatures and reduced summer water availability. Faster growth rates and healthier trees also increase canopy benefits. This study evaluates the early survival, growth, and condition of over 1,000 trees planted between 2019 and 2023 in Davis, California, USA, and compares the performance of species identified as “climate-ready” to more common urban species and native oak trees. Methods Survival was evaluated at the end of the growing season in 3 consecutive years, 2021 to 2023. Trunk diameter, tree condition, and site characteristics were also assessed in 2021 and 2023. Results The overall survivorship was estimated at 86% 4 years after planting. As a group, climate-ready trees had the highest survival, condition, and growth, although survival of native oaks was not significantly lower when site irrigation was considered. Site irrigation was associated with higher survival for all trees and higher growth rates for climate-ready and common trees. Condition in 2021 was a strong predictor of survival, growth, and condition in 2023. Conclusions Planting climate-ready trees is a promising strategy for reaching urban canopy cover goals. Careful tree selection and planting, as well as early watering and trunk protection, are important investments to improve outcomes for survival, growth, and health.