Environmental change leads to increasing selection pressure on the capacity of plants to colonize new areas. Wubs et al. show that the colonization success of the fern Asplenium scolopendrium is linked to its mating system, with selfing rates varying greatly among genotypes. Single-spore establishment of new populations requires selfing genotypes, but later immigrants are more successful if they are outcrossing. The results provide further evidence against the overly simple dichotomous distinction of fern species as either selfing or outcrossing.