Objective Climatic differences among transplanting dates directly affect tobacco plant growth, yield, and leaf quality. This study aims to determine the optimal transplanting time in potential tobacco-producing areas of Shandong Province, including Qingdao, Zibo, and Laiwu, to optimize climate resource utilization and improve leaf quality.

Method From 2022 to 2023, transplanting date comparison trials were conducted in Qingdao, Zibo, and Laiwu, with three transplanting dates: Y1 (April 30), Y2 (May 10), and Y3 (May 20). Agronomic traits at the topping stage, chemical composition of C3F-grade cured leaves, sensory quality, and economic traits were comprehensively evaluated under different transplanting treatments. Regression analysis was performed using meteorological data to identify the optimal transplanting period.

Result The transplanting period significantly affects agronomic traits of tobacco plants, such as plant height, effective leaf number, stem circumference, and leaf morphology, while also influencing the chemical composition of middle tobacco leaves, including reducing sugars, total sugars, nicotine, and the nitrogen-nicotine ratio, as well as sensory quality factors like aftertaste and offflavor. Overall, the Y2 transplanting period performed best in the three tobacco regions, with the healthiest tobacco plants, coordinated chemical composition, and highest economic benefits. Compared to the Y1 transplanting period, the Y2 transplanting period increased the output value per 667 m² in the Jiaozhou, Yiyuan, and Laiwu tobacco regions by 14.94%, 7.51%, and 23.30%, respectively. Regression analysis results showed that the daily average temperature of the transplanting period corresponding to the highest sensory scores and output value per 667 m² in the three tobacco regions was between 18 ℃ and 19℃. Specifically, the optimal transplanting temperatures when the output value per 667 m² peaked in Jiaozhou, Yiyuan, and Laiwu were 18.20℃, 18.85℃, and 19.11℃, respectively, while the temperatures corresponding to the highest sensory scores were 18.34℃, 18.45℃, and 19.01℃, respectively. Further analysis of meteorological data found that although the conventional transplanting time in each production area is from late April to early May, with temperatures typically reaching 15℃, there is still a certain gap compared to the optimal temperature for tobacco plant growth. Therefore, appropriately delaying the transplanting time to better align with the optimal temperature range could improve the growing environment of tobacco plants, enhance leaf yield and quality.

Conclusion The optimal transplanting periods were identified as May 17-20 for Jiaozhou, May 13-16 for Yiyuan, and May 12-16 for Laiwu.