Phylloclimate corresponds to the physical environment actually perceived by each individual aerial organ of a plant population, and is described by physical variables such as spectral irradiance, temperature, on-leaf water and features of around-organ air (wind speed, temperature, humidity, etc.). Knowing the actual climate in which plant organs grow may enable advances in the understanding of plant–environment interactions, as knowing surface temperature instead of air temperature enabled advances in the study of canopy development. This may be particularly relevant for the spatially distributed processes, e.g., the interactions between plant organs and pathogen fungi. Characterizing phylloclimate variables, using experimental work or modeling, raises many questions such as the choice of suitable space- and time-scale as well as the ability to individualize plant organs within a canopy. This is of particular importance when aiming to link phylloclimate and function–structure plant models. Finally, recent trends and challenging questions in phylloclimate research are discussed, as well as their possible applications in plant epidemiology.