AbstractAlthough it has long been acknowledged that seed characteristics are of major importance to the conquest of tree crowns by vascular epiphytes, there is surprisingly little quantitative evidence on the aerodynamic properties of their diaspores. We used a custom-built device to determine the terminal velocity (V_term) of falling seeds, a parameter that has been shown to have high predictive power for the wind dispersal potential of diaspores under natural conditions. We determined V_term of 45 species of epiphytic and terrestrial Orchidaceae, which almost doubles the currently available database for this family. Although varying by a factor of five with values of 0.09–0.4 m s⁻¹, V_term was invariably very slow compared to plants in general. For each species, we also took morphological data and determined seed mass. None of these parameters was linearly correlated with V_term and neither did the average V_term differ between species found in the two habitats, although seeds of terrestrial taxa were significantly larger and heavier. Finally, we demonstrate the potential of our device to measure V_term of even smaller diaspores by successfully quantifying V_term of fern spores. This tool has much potential for the quantitative study of dispersal of plants with tiny diaspores, particularly in a conservation context in fragmented landscapes.