Ants in herb garden.... GRAH!?

One thing to try which is harmless to humans and the soil is something called “Diatomaceous Earth” or “Diatom Powder” which is the microscopic skeletal remains of prehistoric diatoms (small water creatures). You will be able to find it at a pet shop that sells fish (it is used in a type of filter). The powder can be sprinkled on and around the ant mounds. What it does is cut the exoskeleton of the ants and kills them by dehydration. Chances are they will move on to greener pastures. It will need to be re-applied if it rains.