Lycoris radiata (L'Hér.) Herb., a temperate geophyte of Amaryllidaceae, is valued for its ornamental floral display but shows limited adaptation under non-temperate conditions. Despite its horticultural value, its distribution in India remains restricted due to complex developmental phenology and chilling requirements for floral induction. This study evaluated the adaptation of L. radiata to the Terai plains of West Bengal through exogenous application of gibberellic acid (GA₃) over two consecutive years. The GA3 application significantly enhanced vegetative growth and enabled floral transition, which was absent in control plants. Independent of GA3 treatment, changes were also recorded in the developmental stages with age, showing ontogenetic physiological adaptation. Compared to the first year, the vegetative phase extended by one month, while dormancy duration decreased by one month in the second year. Exogenous GA₃ application significantly influenced leaf production and growth (p < 0.001). In the first year, the highest leaf number (30.39) was recorded at 225 ppm, while leaf production rate (LPR) was maximised at 150 ppm (0.296 leaves/day). In the second year, 100 ppm GA₃ produced the maximum leaf number (67.13) and LPR (0.465 leaves/day). Flowering during the first year was minimal, with only one scape observed at 75–150 ppm. Leaf length and growth rate improved in the second year, with maximum leaf length (36.77 cm) at 75 ppm and AGR peaking at 150 ppm (0.201 and 0.471 cm/day in the first and second years, respectively). In the second year, all GA3 treatments induced flowering, with 150 ppm showing the earliest phase transition (285.40 days) and number of flowers per plot (14.67). Growth dynamics and physiological progression were quantified using LPR and absolute growth rate (AGR). These findings establish the role of GA3 in regulating stage-specific growth responses and inducing flowering under non-temperate Terai conditions.