I was warned but I didn't listen.
Three years ago, I planted a 4 inch pot of "Chocolate" Mint (it really does smell and faintly taste like it) in the far corner of my garden area.
It has taken some tips from it's no-doubt distant cousin, the kudzu, and has taken over a 6 x 8 area, mercilessly snuffing out my garlic chives and oregano and is now steadfastly creeping inward toward my cukes.
I took a hoe and a spade to it last year and thought I had established a no-man's land, but it has violated it with a vengeance.
Beware the Chocolate Mint and his ilk, the rest of the mint family...they have no respect for boundries!