Place pine cones around the plants in pots to discourage cats from digging. If necessary, add short stakes to keep the cones from being moved.
dave said:My solution was to go out in the woods and find the canes of thorned plants, like Smilax rotundifolia. Those have really nice thorns. Then cut the stems to length and cover the soil with them. That put a stop to the cat problem in a fast hurry.