Oh vinegar, how you are so near and dear to my heart.
You are delicious, clean the inside of my house naturally, are great for my hair, kill weeds with ease and make my plant pots bacteria and fungus free!
As I was making my yard smell like a pickle factory/fish n'chip shop earlier today I had an epiphany that I might be able to control my mint in my herb bed a little better than my current tin can border method: VINEGAR!
I'm not worried that I will decimate mint (really, really hard to do). So in addition to the tin can border (which I like to believe will control the mint not only physically but maybe by heat that is theoretically absorbed by the can making it inhospitable to the creeping mint underneath), on one of my tin can border, in the inside area where the mint grows I doused a line of vinegar there and between the cans.
A little later in the day and I already see a little line of mint die-off, while the inside of the border stays healthy, fresh and minty!
The mint was relegated to the lower portion of my 2 tiered raised herb bed and slopes downward so I am not too worried about causing any other herbs to die off, assuming that the vinegar doesn't travel far from the original douse point.