Seedling age is a key determinant of plant adaptability at lower altitudes in the threatened Himalayan medicinal herb Arnebia benthamii (Wall. ex G. Don) Johnston

Himalayan mountains host unique alpine species adapted to extreme conditions. Arnebia benthamii , as a characteristic alpine species, constitutes an integral component of the Himalayan Mountain ecosystem. Yet, overexploitation in its native habitat has caused population decline, necessitating conservation through cultivation at lower altitudes. The study evaluated age-dependent transplantation success and post-transplant physiological performance of A. benthamii seedlings transferred from high-altitude polyhouse conditions (2646.32 ± 9 m asl) to a low-altitude polyhouse condition (1,530 m amsl). Seedlings aged 1 (1M), 3 (3M), and 6 (6M) months were assessed for survival, growth (rhizome and shoot development), and biochemical parameters (total phenolics, antioxidant activity, and chlorophyll content). Results showed that 6-month-old seedlings had the highest survival rate (83.33%) and significantly (p < 0.05) superior growth and biochemical traits as compared to younger age seedlings. Six-month-old seedlings were found optimal for lower-altitude transplantation. By linking seedling age with adaptive responses under altered microclimatic conditions, the study offers a practical strategy for large- scale propagation, cultivation and unique opportunity to increase the economy of local farmers.