How do you keep squirrels out of your plants?

I sprinkle hot pepper flakes around the plants. You can buy it cheaply at Costco.

I had to put small rocks completely covering the soil. It has been the only thing that keeps them from digging in mine.

I had a roll of dark screening that I cut to fit the top of my planters. I cut up and bent metal coat hangers to stick into the dirt through the screen to hold it down. I can still water and fertilize the flowers, but squirrels can't get into the dirt. Of course, this would only work for potted plants.

If it's just an issue with them digging in the soil then anything that deters them will work (as mentioned previously). I sometimes have trouble with them eating my plants. I've tried everything I've ever seen online (including the hot pepper flakes which had no affect on my mutant squirrels. It makes sense and maybe it'll work for you).