Hi, Sadly there are no plants that will repel cats. You can try a liquid repellent, the Liquid Fence company makes a good one, but otherwise you might have to resort to a layer of chicken wire over where they prefer to go to the bathroom. If you can keep them from digging a hole to go to the bathroom that will discourage them. I've never tried the liquid repellents, but it might be worth a shot. They are sold at most garden centers or places like Home Depot or Lowes.