Even if your mint is growing in a raised bed, such as a tire, if there is no barrier at the bottom, the roots (runners) will find their way underground and spread, working their way under the tire to the rest of the lawn. In many cases, mints spread aggressively. It’s best to plant them in a pot (you could even place the pot in the center of the tire); you could also sink the pot down so that the rim is just above the soil.
Even if your mint is growing in a raised bed, such as a tire, if there is no barrier at the bottom, the roots (runners) will find their way underground and spread, working their way under the tire to the rest of the lawn. In many cases, mints spread aggressively. It’s best to plant them in a pot (you could even place the pot in the center of the tire); you could also sink the pot down so that the rim is just above the soil.