The transition from the vegetative to the reproductive growth phase is a crucial development process in plants. However, the metabolic changes and the regulatory networks of related genes implicated in the floral transition of perennial plants are poorly understood. Orchardgrass (Dactylis glomerata), a perennial cool-season grass, is an economically important forage grass cultivated worldwide. We analyzed the transcriptome and metabolome data at seven different stages in two cultivars to systematically explore the regulatory network of flavonoid biosynthesis, starch and sucrose metabolism, carbon metabolism, and plant hormone signal transduction to better understand the floral transition of orchardgrass. The hydroxypyruvate reductase geneDgHPR1 of carbon metabolism may positively regulate flowering time by up-regulating key flowering genes, such as AtAP1, AtSOC1, AtFT, AtFUL, and AtLFY. The indole acetic acid gene DgIAA17 exhibited high expression levels from the vegetative growth stage to booting stage. Overexpression of DgIAA17 accelerated flowering time phenotype under both normal and long-day conditions, with significant upregulation of flowering genes such as AtAP1, AtCAL, AtFUL, AtLFY, AtSOC1, and AtSPL3 compared to wild-type plants. These results provide significant insight into the transcriptional control of major metabolites in floral transition and offer guidance for future yield and quality improvement of perennial plants.