The regional tree of life, reconstructing the tree of life to include the regional species pool, has been a research focus in biological science over the past decade. Informed by phylogenetic relationships among coexisting species, a regional tree of life can connect evolutionary and ecological factors during the evolution of a biota and thus has become an efficient tool to trace its temporal and spatial diversification. In this paper, we summarize the application of a regional tree of life in floristic studies in the following three fields: (1) To reveal temporal patterns of a flora by estimating divergence time and evolutionary rates based on the tree of life; (2) To reveal spatial patterns of the biodiversity in a flora and to guide the regionalization of floristic zones by integrating phylogenetic and spatial data; and (3) By integrating biogeographic and environmental data and investigating how taxa respond to paleogeographic events and thus climate change to reveal the underlying ecological, geographical and historic factors of the formation of the floristic biodiversity pattern. In addition, we highlight the relationship between the regional and global tree of life and indicate the potential to identify biased divergence times with incomplete taxa sampling using a regional tree of life. Finally, we suggest that future studies should integrate current mega data at different scales in hotspots to elucidate biodiversity patterns in a worldwide framework.