Mint is useful, fragrant, and easy to grow, but it can also become invasive very quickly. The biggest mistake is planting it directly in open soil without a barrier.
Once its underground runners spread, mint can move far beyond the spot where you wanted it.
Mint grows through underground stems called runners. These stems travel through the soil and produce new shoots, even at a distance from the original plant.
If the soil is moist and the plant is happy, it can expand aggressively during the growing season.
Planting mint directly in a vegetable bed, border, or herb patch gives it too much freedom. It may compete with nearby herbs and become hard to remove completely.
Grow mint in a pot, raised container, or buried pot with drainage holes. Check the edges often and cut back escaping runners before they root.
Harvest regularly to keep the plant compact, but do not rely on cutting alone. The roots still need a physical limit.
Mint becomes invasive when it is planted freely in open soil. A pot or barrier is the simplest way to enjoy it without letting it take over the garden.