The olive (Olea europaea) and the wattles (mimosas or Acacia spp.) are typical tree species of the Mediterranean and Australia, respectively. Both trees have been subject to trans-oceanic movements, including the introduction of Mediterranean olives to Australia, and the introduction of Australian wattles to the Mediterranean. In each case, the trees have naturalised and become problematic invasives. Based on case studies of such movements, we compare and contrast the processes of transfer, dispersal, and genetic changes of these trees, with particular attention to crop-feral-wild complexes in both their home ranges and in introduced areas. Contrasting ecological, social, and economic landscapes shape the possibilities for crop-feral-wild interactions and for invasiveness.