This study deals with energy harvesting from vortex-induced vibration (VIV) of a flexible cantilever plate placed in the wake of a rigid cylinder. Conventionally, the plate is designed to resonate with the vortex shedding frequency behind the cylinder at a given flow velocity. The experimental results presented here show that the frequency of the plate oscillations undergoes an abrupt increase from a low value to a higher value at a critical flow velocity. Numerical simulations carried out in the present study suggest that this jump is due to the transition between two modes of wake oscillations in the system, one with a low Strouhal number range accompanied by impeded shedding and the other being the natural vortex shedding with a higher Strouhal number range. It is also found that the mode of vortex shedding depends on the flow velocity as well as the gap between the cylinder and the plate. There exists a critical gap for every flow velocity below which vortex shedding is inhibited resulting in reduced plate vibrations. The results indicate that the position of the plate in the wake affects the shedding frequency significantly and thus the gap between the plate and cylinder needs to be considered as a key parameter in design of such flow-induced energy harvesters. © 2019, Springer Nature Singapore Pte Ltd.