Passive restoration methods offer great promise for tropical regions where resources are limited but the success of such efforts can be variable. We used trait-based theory to investigate the likely trajectories of passive restoration efforts in a degraded Nigerian montane forest system recently protected from burning and cattle grazing. To test the potential for trees and shrubs to colonise pasture grassland adjacent to forest remnants, we quantified the density and species richness of seed and seedling communities at increasing distances from the forest edge. We then determined which plant traits are responsible for colonisation by quantifying changes in functional-trait dispersion and relative frequencies of dispersal-linked traits with increasing distance from the forest. We found a dramatic decrease in seed and seedling densities and also species richness just beyond the forest edge, with significant turnover in species composition from the forest to adjacent grassland. This was mirrored by a significant decline in functional-trait dispersion and a shift in the relative frequencies of dispersal-linked traits. These findings suggest that the reassembly of plant communities adjacent to remnant forest is dependent on functional traits present in these remnant source populations, providing support for the pragmatic use of trait-based theory in restoration management.