Vertically aligned, dense ZnO nanorod arrays were grown directly on zinc foils by a catalyst-free, low-temperature (450−500 °C) oxidization method. The zinc foils remain conductive even after the growth of ZnO nanorods on its surface. The success of this synthesis largely relies on the level of control over oxygen introduction. By replacing zinc foils with zinc microspheres, unique and sophisticated urchin-like ZnO nanorod assemblies can be readily obtained.