Question
Is there something I can put or spray on the soil of my house plants to stop my cat from using it as a litter box, and not hurt the plants?

Answer
Karen:
I will pass on some tips that I have picked up as a cat lover and a houseplant keeper.  Cats hate the smell of citrus, anything like oranges, lemons.  I have heard that if you place a few lemon or orange peels (just the peels) in the top of the houseplant it is likely to repel them from going near it.  There are also some citrus sprays which are available to purchase at pet stores which would also repel cats, but I wonder about the safety of spraying anything directly ON my plants.  I have not used this tip, but it is definitely a safe one for cats and plants alike, since the peels do not touch anything but the soil.

I like to use pine cones on top of the soil.  Cats despise the texture of them, and because the cones move about if barely touched, cats find them scary.  Aluminum foil wadded up into loose balls are scary to cats, as is a very "crackly" type of plastic wrap. If you find using foil or plastic unsightly you can place stones on the top of the soil.  Cats usually will only eliminate in a place where they can spread the soil or sand to cover their litter, and stones are not movable that way!  Plus, I find that stones add a beauty to plants.

These are a few ideas for you.  I hope they help. Good luck