Wet-chemical synthesis is a promising alternative to the conventional vapour-phase method owing to its advantages in commercial-scale production at low cost. Studies on nanocrystallization in solution have suggested that growth rate is commonly affected by the size and density of surrounding crystals. However, systematic investigation on the mutual interaction among neighbouring crystals is still lacking. Here we report on strong interactive growth behaviours observed during anisotropic growth of zinc oxide hexagonal nanorods arrays. In particular, we found multiple growth regimes demonstrating that the diameter of the rod is dependent on its height. Local interactions among the growing rods result in cases where height is irrelevant to the diameter, increased with increasing diameter or inversely proportional to the diameter. These phenomena originate from material diffusion and the size-dependent Gibbs-Thomson effect that are universally applicable to a variety of material systems, thereby providing bottom-up strategies for diverse three-dimensional nanofabrication.