Digging in flower pots can just be foraging behavior or it can be
seeking moisture. Try leaving bowls of water about to see if that stops
it.

Also a spray made from cayenne and garlic discourages both squirrels and
deer. Deer ate the blooms off my impatiens all summer long until I began
the spraying. Boil a teaspoon of cayenne and garlic powder in a pint of
water. Strain and spray. Repeat after rain.

I had a neighbor some years ago who protected their pecans from
squirrels by the draconian measure of shooting a squirrel in the Fall
and nailing it to the tree. Harsh but effective.