Ecological study of cliff environments has steadily increased in the last three decades. However, plant communities on many cliffs have yet to be investigated, and there remains uncertainty about the mechanisms that drive vegetation patterns on cliffs. On the Trapps cliff, a renowned rock-climbing destination within Mohonk Preserve, New York, we recorded tree species and surface micro-topography (“sloping.” “level,” “incut”) along seven rappel transects. In two study areas, we also sampled the ridge and talus areas above and below the cliff transects, and in one of those areas, we included a separate lateral survey along a prominent ledge on the cliff. We used estimated diaspore (seed or fruit) weights and chi-square analyses to test for association between diaspore weight class and topographic categories across the entire study. The cliff tree communities were dominated by mature pitch pine (Pinus rigida) and more frequent but smaller-diameter sweet birch (Betula lenta). Sweet birch, a species with lightweight, wind-dispersed seeds, was disproportionately frequent on the cliff and on sloping surfaces on the cliff, while heavier, gravity-dispersed diaspore species (especially oaks) were underrepresented on the cliff in general, but disproportionately associated with level micro-topography on the cliff. Our results suggest that diaspore weight and associated dispersal mechanisms may play a role in the assembly of cliff tree communities that are divergent from the ridge above, or talus below. Management implications include protecting adjacent plant communities (ridge, talus) that are likely diaspore sources that sustain plant communities on cliffs.