I have adopted my daughter's cat, Ninja, after he started peeing outside the litterbox. She didn't want to banish him to live outside since they live close to a road. I don't want him to live outside here because I am almost sure i have lost a cat to coyotes soon after my husband and i moved here. I still feel terribly guilty over that. That cat was banished outside because of litter box avoidance. Ninja has been living with me for a little over a year. While I have been away for a few weeks, i think Ninja has regressed. Not sure yet. Husband didn't change litter boxes while I was away. Ninja peed just outside the litter box and near a potted plant. My daughter said she has caught Ninja peeing in one of her plants while he was still living with her. My daughter and i discussed reasons why - litter box not being cleaned often enough? or not enough attention from her? or kids being too noisy? Whatever the reason, he's a wonderful personable cat, and i feel lucky to have him with me. Anyway, I have NOT tried putting potting soil in a litter box yet. All litter boxes are clean and refilled with unscented non scoopable litter and cat attract sprinkled on top. That is my usual routine. I wanted to try my normal litter box routine first and watch his behavior. In the meantime, I would very much like to know if anyone has used potting soil as litter. How often does the litter box have to be changed if potting soil is used?