A green roof module for covering a portion of a roofing surface with vegetation, includes a tray for containing a growing medium and vegetation, a permeable membrane, and a drainage board The tray has a biodegradable bottom and a plurality of upwardly extending biodegradable walls about the perimeter of the biodegradable bottom The biodegradable bottom is configured so that water received within the tray can pass therethrough The permeable membrane is provided below the biodegradable bottom, and is sized and shaped so as to span the biodegradable bottom and configured to allow water to pass therethrough while inhibiting the growing medium from passing therethrough The drainage board is provided below the permeable membrane opposite the biodegradable bottom, and has an upper surface for supporting the biodegradable bottom and being surrounded by a plurality of edges The drainage board is configured so that at least some of the water passing through the permeable membrane and received on the drainage board will be drained away from the tray.