If it is not too late flush it well with cool water and then hope for the best. It may recover.

Otherwise try to make it into a positive learning experience.

Dave

My first thought is to flood it with cool water but it may be too late. I hope he won't feel bad-we all learn some things the hard way.

Explain to him that the very, very best gardeners kill more plants than anyone else. It's because the experts are always experimenting and trying new things. So he's on his way to becoming an expert! If you learn from your mistakes, then they are not mistakes. It's only a mistake if you don't learn.

Gardening is all about experimenting. I hope he continues to garden. In 20 years the tomato plant will be something you can laugh about together, over a plate of the fabulous vegetables he has grown. :^)

It depends on how near/ far the ant hill was from the plant.
Also the roots grow around the plant, 360 degree. So hot water may have killed some of the roots but not all of them.

It would be too late for cold watering to do any help after the fact.The damage is nor reversible, IMO.

Thanks everyone! We tied up all of the vines, so that they were at least off the ground, and today the plant seems to be doing much better - even starting to sprout little suckers again :). I was worried, because the anthill was only inches from the base, but some of the roots must still be ok.