Abstract: This study investigated the impact of grafting on the flowering of Handroanthus impetiginosus, comparing two grafting combinations: P/P (Handroanthus impetiginosus scion + Handroanthus impetiginosus rootstock) and P/Y (Handroanthus impetiginosus scion + Handroanthus chrysanthus rootstock). The results demonstrated that the P/Y combination entered the budding stage 46 days earlier and the flowering stage 33 days earlier than the P/P combination, with a flowering duration extended by 17 days. Furthermore, the P/Y combination exhibited significantly higher numbers of flowering branches, inflorescences, and flowers compared to the P/P combination. Analysis of nutrients and endogenous hormones suggests that P/Y grafting achieves earlier flowering, increased flower quantity, and a prolonged flowering period by regulating soluble sugars and hormone levels, including IAA, GA₃, and JA.