How can you rid your garden of mint?

If it is mixed in with other plants you don't want to kill, Roundup makes a foam you can spray on the leaves of the mint, it will be absorbed down into the roots, and kill just that plant. If you want to kill mass quantities, spray with either Roundup, a cheap glyphosate substitute for Roundup (everyone makes one), or 2,4-D. This kills it to the roots, and it won't come back. Remove the plants after the tops turn yellow and die back (after the chemical has been taken up), usually a week to 10 days or so, depending on the weather (it affects how quickly the chemical is absorbed). You might want to contain mint better the first time, which is to restrict its growth by planting it literally in a large black plastic nursery pot, say a 15-gallon size, sunken into the ground in your herb garden, so the roots won't spread. You'll have to thin it out with a digging fork or shovel every now and then. Give it to your friends, teach THEM how to plant it so it won't spread, too! Or donate it to the local garden club whenever you thin it out. Someone will love you for it.