If it's garden plants you can't just put some toxic pesticide in there. I have used boiling water before. It works well but is kind of a pain.
I have some strawberries in tubs and got a big nest in one of them. I walked into the barn and spotted some Chlorine pool tabs on the shelf.
These things stink right through the jug. I put one tab down into the hill and left it for about 3 -4 days. ( no rain) Ants left the premises and
I put the tab back in the jug. I hope this continues to work.

Wake up gardeners ! Spring comes right after Christmas.