Old cultural landscapes, such as old parks and gardens, can be expected to be rich lichen habitats, as they offer otherwise rare microstructures and a high habitat continuity. Yet, old parks are not well studied with regard to their lichen flora. In this study, we investigated three old castle parks in southwest Germany and recorded the epiphytic (bark-inhabiting) lichen flora on 205 native and non-native trees, belonging to 63 tree species. We surveyed lichens on tree stems and assessed tree diameter, bark furrow depth, bark type, and bark pH. We investigated species diversity patterns using a rarefaction/extrapolation approach and community composition using non-metric multidimensional scaling (NMDS). Then, we analysed patterns in species richness and community composition using generalized linear mixed effect models (GLMMs) and a permutation-based, multivariate ANOVA. Species richness was mainly affected by tree species identity and tree functional group, with highest species numbers recorded for Tilia spp., and deciduous trees hosting significantly more species than evergreen trees. Community composition was mainly affected by tree species identity and marginally by bark pH and bark furrow depth. Most lichen species were generally common epiphytes, with many species being indicative for eutrophication or high temperatures. In contrast to our expectation, rare or red-listed species were only rarely encountered. In summary, our results show that the epiphytic lichen communities in old parks are shaped by internal factors (i.e. tree species identity, tree microhabitats) and external factors (i.e. eutrophication, macroclimate). Based on our study results, we recommend maintaining a high (deciduous) tree species diversity, as different tree species hosted different lichen communities. Keywords: Urban mycology · Century-old cultural landscapes · Habitat continuity · Indicator species · Non-native trees · Natural collections.