Alpine treelines globally may move upslope due to climatic warming. Such movement would initially need seed germination and seedling establishment above current treelines. In a recent study published in AoB PLANTS, Loranger et al. studied these processes experimentally in five common European treeline tree species. Surprisingly, each species responded very differently to moisture and temperature gradients, with positive and negative responses possible. These results match the heterogeneity observed in treeline dynamics and spatial patterns globally. They strongly emphasize the need for species-specific parameterisations in predictive models of treeline responses to climatic change.