Plants are strongly influenced by their surrounding environment, which makes them reliable indicators of climate and ecology. The relationship between climate, ecology, plant traits and the geographic distribution of plants based on their climatic tolerances have been used to develop plant-based proxies for reconstructing paleoclimate and paleoecology. These proxies are some of the most accurate and precise methods for reconstructing the climate and ecology of ancient terrestrial ecosystems and have been applied from the Cretaceous to the Quaternary. Despite their utility, the relationships between plant traits and climate that underlie these methods are confounded by other factors such as leaf life-span and phylogenetic history. Work focused on better understanding these confounding factors, incorporating the influence of phylogeny and leaf economic spectrum traits into proxies, expanding modern leaf trait-climate and ecology calibration datasets to additional biogeographic areas and climate regimes, and developing automated computer algorithms for measuring leaf traits are important growing research areas that will help considerably improve plant-based paleoclimate and paleoecological proxies.