Put peppermint or rubber snakes
Any type of hot spice, the hotter the better. Works great!
Sprinkle some "Blood Meal" around the base of the plants and this should deter them from digging.
I go to the Dollar store and buy cheap plastic forks. Snap off the handle and poke them in the dirt tines sticking up. (sometimes I leave the handles on, depending on the depth of the pot). Squirrels don't like getting poked while they are sniffing around trying to find a place to bury their nuts. Although, my Grandkids can't figure out why I plant forks every year :-)
My friends and I use river rocks. Any home improvement center, landscape supply or quarry will have what you need. We just choose rocks big enough that they can't shove them out of the way. Place on top of soil in your pots and boxes. And it is entertaining to sit and watch them try!