The dataset originates from an experiment aimed to investigate the genetic diversity of perennial ryegrass phenology in response to different environments. In particular, we studied effect of duration of exposure to non inductive treatments on leaf elongation and appearance rate, spikelets production and heading date. This work provides original data for perennial grasses and highlights the interactions between the vegetative and reproductive development. Our results could be used to develop and/or calibrate phenological models of grasslands.