Whilst a good green roof designed for biodiversity will be attractive to many pollinators, providing nesting habitat is also an important consideration. Green roofs not only provide adequate forage for pollinators, but can also provide nesting for some species in the substrate. Tawny mining bees are known to mine nest holes in green roof substrate if it is relatively compact. Many interesting solitary bees however, do not nest in the ground. Providing habitat walls in the form of bee hotels is a relatively simple thing to do.