Quercus, commonly known as oak, has great potential as one of the most widely cultivated plant species. However, the lack of superior varieties is a bottleneck for its usage and application in Southwest China. Here, this study aims to explore the growth and photosynthetic traits of 18 oak varieties with the goal of identifying the adaptable superior varieties for the region, focusing on nutrient growth, leaf morphology, chlorophyll content, and photosynthetic parameters over a 32-week growth period. The results showed that a significant diversity was observed among the varieties. Growth rhythm and fitted curves divided the 18 oak varieties into three patterns. Additionally, for the leaf morphological parameters, Q. denta boasted the maximum leaf area (167.24 cm2), leaf width (13.62 cm), and leaf aspect ratio (156.6); Q. mongo showed the greatest leaf length (20.37 cm); while Q. acutis had the largest leaf form factor (3.44) and leaf gap (0.39). Chlorophyll content was based on three-time-points investigation, with higher levels observed in Q. mongo, Q. robur 4, Q. wutai, Q. denta, Q. acutis, and Q. robur 1. The transpiration rate (E) (5.03 mmol m−2), stomatal conductance (gsw) (0.22 mol m−2 s−1), and total water vapor conductance (gtw) (0.19 mol m−2 s−1) were dominantly obtained in Q. robur 1, while Q. denta exhibited the highest intercellular CO2 concentration (Ci) (564.67 µmol mol−1). Conversely, Q. wutai displayed a significantly higher leaf chamber CO2 concentration (Ca) (502.11 µmol mol−1). Furthermore, growth traits showed a correlation with leaf morphological and photosynthetic traits. PCA analysis grouped the oak varieties into five clusters, with Q. acutis, Q. robur 1, Q. palus 3, Q. denta, Q. nutta, Q. mongo, and Q. wutai identified as superior varieties. These findings not only offer promising oak candidate varieties for Southwest China, but also provide insights for establishing efficient breeding program for other woody plants.
