Abstract: To determine the optimal transplanting time for standardized cultivation of Melastoma dodecandrum and address low yield and unstable quality caused by unclear transplanting schedules, one-year-old cuttings of M. dodecandrum were used as experimental materials. Four transplanting treatments were established: March 25 (T₁), April 25 (T₂), May 25 (T₃), and June 25 (T₄), with a randomized block design adopted. The effects of different transplanting dates on growth indicators, yield, and medicinal component contents of M. dodecandrum were investigated. The results showed that transplanting time significantly affected plant growth, yield and accumulation of medicinal components in M. dodecandrum. With delayed transplanting, the branch number per plant, main stem length, branch length, leaf number per plant, single leaf area, leaf area index (LAI), yield, and contents of medicinal components (gallic acid, vitexin, isovitexin and rutin) all exhibited a decreasing trend. Among all treatments, T₁ presented the best growth performance, and its branch number per plant, main stem length, leaf number per plant, LAI, fresh and dry shoot biomass per unit area, as well as medicinal component contents were higher than those of other treatments. T₄ obtained the lowest values for all measured parameters. Except for non-significant differences in protocatechuic acid content and leaf SPAD value, most growth, physiological and medicinal component indicators decreased significantly under T₄. In conclusion, under open-field cultivation conditions in Nanchang area, the suitable transplanting time for M. dodecandrum is late March. Transplanting within this period can remarkably promote plant growth and increase yield and medicinal component contents. This study provides theoretical basis and technical support for formulating operating procedures for the standardized cultivation of M. dodecandrum.