I need to repot my sweet grass but I can't because the root mass is loaded with ants and I don't want them crawling all over me when I do it.

I tried drowning them but the plant is too big so I couldn't submerge the entire thing and thus, it still has ants.

I've been told that sweet grass (Hierochloe odorata) is sensitive to harsh chemicals so I'm hesitant about what to use to kill the ants without killing my sweet grass.