Poppy, you may like to hear what i do to be safe from rats. They do like bare ground to did their holes (spherical tops) so I use ground cover a lot in my large garden, although "weeds"left to do there own thing will do it too, but I prefer the pretty ones like yellow archangel, acaena microphylla, perennial sweet peas, the poached egg plant, phacelia, etc. No sign of rat holes when the ground is covered! My resident fox is a great help too. If I ever see a bare patch I rush to plant something in it because I have never forgotten the stench from the dead rat I had once under the floor boards.