This paper discusses an experimental study of vertical mixing in an aquatic canopy. Vertical variation of physical characteristics of stems is fairly observed in the field and leads to variation in frontal area. This can affect both the flow and the mixing process. We experimentally investigated the effects of vertical density variation on both flow and vertical diffusion at high Reynolds numbers (turbulent flow range). Using rigid cylinders, we simulated step-like density variation in a flume. Vertical mixing coefficient was measured by recording vertical mixing of dye in the flume. The results indicate that vertical mixing coefficient decreases as density increases in depth. Velocity profiles collected from ADV records are in good agreement with theoretical predictions at high Reynolds numbers. Formation of vortex structures as strong as those produced in the shear layer of submerged canopies was not observed in these experiments, and the effects were limited to the interface.