Several attempts have been made to generate complete species-level phylogenies for large clades, enabling comprehensive analyses of ecological or evolutionary hypotheses at the species level. No such phylogeny has, however, been generated for any major plant group yet, but here we generate such a phylogeny for the palm family (Arecaceae). We do this using a novel Bayesian approach, estimating the validity of intra-generic taxonomic groupings as topological constraints to assist in placing species without genetic or morphological data. From these we implement those that are supported by genetic or morphological data for a given genus or for related genera. The intergeneric relationships in our new phylogeny are surprisingly different from earlier phylogenies in the placement of genera within tribes, but largely identical to previous findings in the deeper branches in the phylogeny, pointing to the need for incorporating phylogenetic uncertainty in analyses based on this phylogeny. Initial analyses of the new phylogeny suggest non-constancy in diversification rates over time within genera, with an apparent increase in diversification rate over time, but no evidence for any geographic variation in the magnitude of this increase. We hope that our study will stimulate further evolutionary or ecological studies using palms as study organisms as well as discussions of the optimal way to place the many species without genetic or morphological data.