I recall when I was a child, we used to pour boiling water on ants, when they ventured inside the house, and that did the trick. But, I'm not sure what that might do to the plant. I would think the most straightforward method would be to lift the plant, dump out the soil somewhere, and re-plant in new, clean container soil, even if the planter is a very large one. You may find that there are some type of aphids, or other food source, for the ants, on or around the roots of the plant, and that is why they are calling your container home, so you should take a close look at the plants when you remove them.

Philomena

When that happens to my planter boxes, I move them around. The ants don't like the movement, and leave. I use a hose to wash all the eggs they are protecting, off the pot and deck. There are insecticides you can put into the soil to kill insects. Around the outside of my house there are ants in every square inch of soil, on the trees, in pots, everywhere.

I use 'Neem'. It is an indian concoction used for everything from lice to antibacterial. You can get it online, or at any indian supply store. It's goopy and stinky. I use a capfull per quart. Spray it generously on the ants and in the holes. Worked for me on ants in my banana trees and spider mites on my indoor over wintering plants. It's a natural also.