Virginia, i had this same problem years ago and the only way i was finally able to get rid of the smell was to replace all the soil. When possible, and without coming on too strong, share with your neighbors why you keep your cats indoors. Set them on sheets of aluminum foil, cats hate the feel and the noise. Have any of you had this happen with your cats? what did you do to stop them from doing it? i’ve heard of pine cones, putting spiney cactus in the pots as well, i’ve even heard of double sticky tape. In fact, this was our first experience with a female cat not using a litter box. Some members of the family wanted to banish said cat from the house, we refused and dedicated ourselves to solving the problem. The cat is 15 yrs old and has not used the plants in years.
It seems to be working so far. Fill a squirt bottle with cold water and spray your cat every time he goes near your potted plants.