Perennial grasses have potential in the production of biofuels, and modulating plant microbiomes may enhance plant growth and productivity, and resilience to environmental stresses. However, our knowledge of the phyllosphere microbiome is limited, in particular for agricultural crops. In this study, Shade and colleagues investigated the assembly and seasonal dynamics of bacterial and archaeal microbiomes of the leaf surfaces and the associated soils of switchgrass and miscanthus across the two growing seasons in 2016 and 2017. They identified core leaf taxa for each crop and season based on abundance and occupancy, including several Proteobacteria (Methylobacterium spp., Sphingomonass spp. and Pseudomonas spp.) and Bacteroidetes (Hymenobacter spp.). Further analysis enabled them to identify seasonal trends of the core leaf taxa (that is, early, mid, and late season groups), which might be linked to plant development.