Under the context of global warming and rising atmospheric CO₂ levels, increases in vegetation leaf area and longer growing seasons both contribute to a clear greening trend. However, whether these two factors show a trade-off or work together remains unclear. In this study, we used multi-source remote sensing data to analyze the patterns of maximum leaf area index (LAImax) and growing season length (LOS) in deciduous broadleaved forests (DBF) across China from 2003 to 2020. The results indicated that: ① An increase in leaf area is negatively correlated with the extension of the growing season. In Northeast China, deciduous broadleaf forests show relatively small increases in leaf area but more significant extensions of the growing season. Conversely, in the northern transitional zone, the opposite pattern is observed, suggesting a trade-off between these two strategies. ② Tree height plays an important role in explaining this trade-off. In the northern transitional zone, where dwarf trees dominate, forests tend to adopt a strategy of increasing leaf area with only small changes in growing season length. By contrast, in Northeast China, where tall trees are more common, forests are more likely to extend the growing season while showing limited leaf area change. This spatial difference reflects the contrasting physiological adaptations of trees with different heights. ③ These contrasting strategies are jointly shaped by climate factors and vegetation traits. Rising atmospheric CO₂ is more likely to promote leaf area increase in dwarf trees, whereas higher surface temperature has a stronger effect on growing season extension in tall trees. In addition, dwarf trees generally have lower initial leaf area and a higher leaf-to-sapwood area ratio, which favors leaf area increase, while tall trees tend to extend the growing season because of their larger basal leaf area and lower leaf-to-sapwood ratio. ④ The two strategies have different ecosystem consequences. Dwarf trees can enhance photosynthesis and ecosystem productivity by increasing leaf area. In contrast, tall trees mainly adapt by extending the growing season, but their lower photosynthetic efficiency may reduce ecosystem productivity.This expansion provides additional context to the ecological dynamics, emphasizing how specific strategies driven by tree height and climate factors interact to shape vegetation function across regions.