Hydrothermal growth has emerged as a popular method for growing ZnO nanorods. Solution concentration can have a significant impact upon the microstructure of the resulting nanorods, and this has been investigated in a high concentration regime by growth at low temperatures (90 °C) on seeded substrates. X-ray diffraction and scanning electron microscopy (SEM) analysis were used to characterize the structural properties of the ZnO nanorods. Optical and electrical properties of the nanorods are also discussed. SEM image analysis revealed that the ZnO nanorod diameters increased linearly with concentration up to a maximum of 104 nm at a concentration of 0.075 M after which the diameter remains unchanged with further concentration increase. Axial growth rate was also found to increase with concentration allowing nanorods to achieve lengths of nearly 600 nm for solution concentration of 0.1M. The number density of nanorods showed inverse behavior to that of diameter. The resistivity of the nanorods was found to decrease with concentration upto 0.075M showing a minimum value of 5.85 x 10‾¹ Ω-m. The growth process has been quantitatively modelled in terms of the dependence of nucleation rate on concentration using the Avrami equation. The nucleation rate was found to be nearly independent of solution concentration showing that the nucleation process is reaction limited. The growth model may therefore be applied to the solution growth of other materials where steric hindrance is significant.