Mint is a robust and fragrant herb known for its rapid, spreading growth habit. This aggressive tendency is primarily due to specialized horizontal stems known as runners, or stolons, that travel along or just beneath the soil surface. Propagating mint from these runners is the most reliable and common method, as it ensures a genetic clone of the parent plant. This technique is far more efficient than growing from seed because the runners already possess the structures necessary to form an independent plant.
Identifying and Harvesting Runners
To begin propagation, locate the runners extending from the main mint clump, which appear as thin, flexible stems growing horizontally near the soil line. These stems are distinct from the vertical, leafy shoots harvested for culinary use. The most important feature to look for are the nodes, which are slightly swollen points along the runner where leaves, aerial roots, or new vertical shoots emerge. These nodes contain the meristematic tissue necessary for new root development.
For successful harvest, use clean, sterilized shears to cut the runner, separating a segment from the main plant. Each harvested segment should be approximately six to eight inches long and must contain at least one to two healthy nodes. It is often beneficial to gently pull away the soil to reveal a section of the runner that has already developed small, pale roots or root initials at the nodes, indicating a high potential for quick establishment.
Planting the Runner Segments
Once harvested, the runner segments can be rooted using two primary methods: directly into a growing medium or in water. For planting directly into soil, a well-draining potting mix is recommended, often a blend of coconut coir and perlite to ensure aeration and moisture retention. Lay the runner segment horizontally on the surface of the moist soil and cover it with a shallow layer, no more than half an inch deep, ensuring the nodes maintain firm contact with the damp medium.
A common recommendation for mint is to plant it in containers, even if the container is sunk into the ground, to prevent its highly invasive root system from spreading uncontrollably throughout the garden bed. When planting in a pot, use a container with adequate drainage. Alternatively, the runners can be placed in a glass of water, ensuring that only the nodes and the bottom portion of the stem are submerged, while keeping all leaves above the water line to prevent rot.
Post-Planting Care for Establishment
Successful establishment of the new mint plants relies on maintaining an optimal balance of moisture and light in the initial weeks. After planting in soil, the growing medium should be kept consistently moist but never saturated, as waterlogged conditions can lead to stem or crown rot. Instead of drenching the soil, a twice-daily misting can help maintain the high humidity levels that encourage root growth from the nodes.
For the first week to ten days, position the newly planted runners in a location that receives bright, indirect light, avoiding direct, intense sunlight. Once new vertical leaf growth becomes visible, which often occurs within one to two weeks, this signals that the roots have successfully formed and the new plant is establishing itself. At this point, the young mint can be gradually moved to a location that receives more light, ideally partial sun, to support vigorous growth.