The gene silencing by sense and antisense transgenes in plants is an effective method to breed new cultivars. Torenia fournieri Lind. is an ornamental plant in the family Scrophulariaceae. We have established a transformation system for Torenia and modified flower longevity and color by transformation-mediated gene silencing. The introduction of a fragment of the ACC oxidase gene, in sense or antisense orientation, allowed the production of transgenic Torenia plants with extended flower longevity. The extended flower longevity was linked to the existence of the transgene. The introduction of a chalcone synthase (CHS) or dihydroflavonol-4-reductase (DFR) gene, in sense or antisense orientation, allowed the production of transgenic Torenia plants whose flower color had been changed. Some transformants showed a pastel flower color, and one showed a wavy pattern on the flower lip. These characters do not exist in normal cultivars.