@dunnmom I put cinnamon in my quilt box to prevent ants from nesting in my beehive and it worked pretty darn well. So it's possible it may work in your garden, though I have heard that it must be dry... But I am not so sure. In a beehive one can't use any sort of serious repellents because bees and ants are so closely related. The cinnamon ended up doing the trick and the bees were content with a box of cinnamon above their heads.
You can also pour big pots of boiling water into their nests to try to flush them out and kill them without really harming the plants etc.