Lichens from an unusually large, arborescent runner oak (Quercus pumila) from Miami-Dade County, Florida, were collected and inventoried. A total of 56 lichen species and one lichenicolous lichen species were found, representing 17 families with Graphidaceae bearing the most (14) species. Several species recorded were also recently reported or newly described from South Florida, which has a tropical climate and ecoregion that are distinct in the continental United States. Some lichen species (especially crustose Arthoniaceae and Graphidaceae) are twig specialists not normally found on trunks and branches; therefore, future studies of lichen diversity on single trees should include as much twig material as possible.