Mint, belonging to the Mentha genus, is a popular aromatic herb known for its refreshing scent and wide use in cooking and beverages. Anyone considering adding it to a garden must understand its highly aggressive nature, as it is known for its rapid, relentless spread in open soil settings. Understanding the plant’s biological mechanism for growth is the first step toward successful management.
The Mechanism of Mint’s Spread
The invasive behavior of mint is rooted in its specialized reproductive biology, allowing it to colonize large areas quickly. The plant primarily uses horizontal, modified stems known as rhizomes, rather than seeds, for propagation. These rhizomes grow just beneath the soil surface, acting as underground runners that extend rapidly away from the original plant.
These subterranean structures send up new, genetically identical shoots at various points along their length. A single rhizome can travel several inches or even a foot in a growing season, establishing new mint patches far from the parent plant. This prolific system makes the plant highly resilient; pulling visible stems only removes the top growth, leaving the extensive underground network intact and ready to resprout within days.
Strategies for Successful Containment
Successful cultivation depends entirely on preventative containment implemented at the time of planting. The most reliable method involves planting mint within a physical barrier that restricts the outward growth of its rhizomes, preventing underground runners from escaping into surrounding garden beds.
A common technique is to plant the mint inside a pot or bucket and then bury the entire container into the ground. The container must be deep (ideally 10 to 15 inches) to accommodate the root ball. Drainage holes must be sealed or covered with a fine mesh to ensure rhizomes cannot push through and contact the native soil. Additionally, the top lip of the buried container should sit a few inches above the surrounding garden level to prevent runners from arching over the rim.
Other Containment Methods
Specialized root barriers made of durable plastic or metal can be sunk vertically into the soil around the planting area. These barriers must extend at least a few inches above the soil line to prevent runners from growing up and over the edge. Cultivating mint in dedicated raised beds that have a solid, impermeable bottom layer separating the soil from the ground below is another secure choice.
Planting in above-ground containers placed directly on hard surfaces, such as patios or paved walkways, offers a reliable solution. This setup physically isolates the mint’s root system from any adjacent garden soil. Regular maintenance is still necessary to trim any trailing stems that might attempt to root themselves in the nearby ground.
Eradicating Unwanted Growth
If mint has already breached containment, the primary corrective action is thorough physical removal of the entire root system. Digging out the area requires reaching a depth of at least 12 inches to ensure all rhizomes are extracted. It is important to sift the soil meticulously, as even small fragments of a rhizome can generate a completely new plant.
Solarization and Chemical Control
For larger, heavily infested areas, a non-chemical method called solarization can be highly effective. This involves cutting the mint down and covering the area with clear plastic sheeting, sealed tightly around the edges. The plastic traps solar energy, raising the soil temperature high enough to “cook” the remaining roots and prevent regrowth. This process requires maintaining the cover for four to eight weeks during the hottest part of the summer.
As a last resort for severe, widespread infestations, chemical control using a non-selective herbicide can be applied directly to the established foliage. Multiple applications are often necessary, as the waxy coating on mint leaves and the persistent underground rhizomes make single treatments ineffective. Always follow the product label instructions precisely, noting that nearby desirable plants may suffer damage from contact.