Potential allelopathic effects of alien Acacia melanoxylon and indigenous Olea capensis subsp. macrocarpa on germination of Acacia melanoxylon

•Alien Acacia melanoxylon germination is not inhibited by leachates of itself or a common Afrotemperate Forest overstorey species.•Acacia melanoxylon showed high viability (90%) and an average germination rate of 67%.•The insensitivity of Acacia melanoxylon to allelopathic leachates likely facilitates it establishment in Southern Cape Afrotemperate Forest.