Highly ordered self-assembled silver nanoparticle (NP) arrays have been produced by glancing angle deposition on faceted c-plane Al₂O₃ templates. The NP shape can be tuned by changing the substrate temperature during deposition. Reflectance anisotropy spectroscopy has been used to monitor the plasmonic evolution of the sample during the growth. The structures showed a strong dichroic response related to NP anisotropy and dipolar coupling. Furthermore, multipolar resonances due to sharp edge effects between NP and substrate were observed. Analytical and numerical methods have been used to explain the results and extract semi-quantitative information on the morphology of the NPs. The results provide insights on the growth mechanisms by the glancing angle deposition. Finally, it has been shown that the NP morphology can be manipulated by a simple illumination of the surface with an intense light source, inducing changes in the optical response. This opens up new possibilities for engineering plasmonic structure over large active areas.