I have a small front garden, which is currently bare whilst I decide what to plant. However, it has become a cat toilet (to at least one with clear digestive issues). I'm going to clear it all up tomorrow with big gloves and a spade but is there anything I can do/plant quickly to deter the local pussies. I'm reticent to use the ultrasonic things as I'm on a road and don't want to scare them in front of a car/bus - they're a pain with their pooing but I'm a cat lover with my own two indoor overlords.