We report the hexagonal wurtzite crystalline structure of ZnO nanorod growth by hydrothermal chemical wet synthesis at low temperature (90 C). We have used p-Si (100), n-Si (100), -quartz (0001), MgO (0001) and ITO (polycrystalline) substrates to understand the growth mechanism of ZnO nanorods with a low pressure environment. X-ray diffraction study confirms the hexagonal structure of the ZnO nanorod. Scanning electron microscopy (SEM) also shows the hexagonal structure along with different size and width of the nanorods. The substrate effect of nanorods has been explained on the basis of adatom kinetics during the growth. We observed that the nanorods were grown from a single nucleation point with 4-5 different branches on the ITO substrate with uniform length and width, whereas MgO substrate shows curled flower architecture across the whole area. The photoluminescence illustrates strong substrate effect. A wide range of UV emission bands along with visible emission has been observed from the ZnO nanorods deposited on different substrates.