My monster mint is on a rampage yo. My spearmint is currently the biggest culprit but other varieties I grow in my garden are proliferating to science fiction proportions.
Those of us who grow our own herbs know that, unless contained, fresh mint can run rampant in a garden. It returns every year with a vengeance. Mine even escapes the raised bed in PA, then it jumps outside the garden enclosure and starts rooting on the lawn outside. It's a mint war at my place I tell ya.
When I expanded my mint variety to include, apple mint, chocolate mint, pineapple mint, orange mint and spearmint, I made sure I grew these in large pots instead of planting them in the ground. I do this both in NYC on our terrace and in the country because if mint has space, it will take it and run.