ZnO nanobundles were grown via a nano-templating technique over a porous silica bed using an aqueous chemical route. The growth of nanobundles initiated from ZnO nano-seeds positioned at various levels over a nanoporous matrix of self-assembled polymethylsilsesquioxane nanoparticles. Bundles of different features like nanowires, nanorods and nanotubes with a high surface roughness were grown over these templates by a day-long incubation in an aqueous solution of hexamethylene tetra-amine and zinc nitrate. We envisage these ZnO nanostructures for sensitive hydrogen detection. Photoluminescence spectra indicate the nanotubes to be most sensitive towards H_2. We observe high reconditionability, moderate sensitivity and a temperature dependent charge carrier reversal phenomenon.