Spearmint container growing guide to prevent invasive spreading in your garden bed every year

Growing spearmint in containers is the most effective way to prevent its notoriously invasive spreading throughout your garden bed. Spearmint, like many mint varieties, has aggressive rhizomes that can quickly take over, pushing out other plants and becoming a persistent weed. By confining it to a container, you create a physical barrier that stops these runners from escaping.

The first step is to select the right container. Choose a pot that is at least 8-10 inches in diameter and depth. This will give the spearmint enough room to grow and develop a healthy root system without becoming overly root-bound too quickly. Terra cotta pots are a good choice as they allow for better air circulation and drainage, which mint generally prefers. However, plastic pots are also suitable, and they retain moisture longer, which can be beneficial in hotter climates. Ensure the container has drainage holes at the bottom. If you are using a decorative pot without drainage, you will need to drill holes yourself or place a smaller nursery pot with drainage inside the decorative one.

Next, prepare your potting mix. Spearmint is not particularly fussy about soil, but it thrives in well-draining soil. A good quality potting mix, perhaps amended with a bit of compost or perlite, will provide the necessary nutrients and aeration. Avoid using garden soil directly in the pot, as it can become compacted and hinder drainage, leading to root rot.

When planting your spearmint, whether it's from a nursery plant or cuttings, ensure the roots are well-covered with the potting mix. If you are transplanting a spearmint that is already in your garden bed and you want to move it to a container, carefully dig it up, making sure to get as much of the root system as possible. Inspect the roots for any stray runners that might have already escaped and trim them.

Position your containerized spearmint in a location that receives adequate sunlight. Spearmint generally prefers full sun to partial shade. In very hot climates, some afternoon shade can prevent the leaves from scorching. Consistent watering is key, especially during dry periods. Water thoroughly until water drains from the bottom of the pot. Allow the top inch of soil to dry out slightly between waterings. Overwatering can lead to fungal diseases, so good drainage is paramount.

To further ensure containment, especially if you have a history of mint escaping even from pots, consider a double-container method. This involves placing the spearmint in a smaller pot, and then submerging that pot into a larger container filled with soil. The outer container acts as an additional barrier. Alternatively, you can plant the spearmint directly into a container with a thick plastic liner that has been punctured with drainage holes. This liner acts as a physical barrier against the rhizomes.

Regularly check the roots of your spearmint. As mint grows vigorously, it can become root-bound. If you notice roots circling the pot or growing out of the drainage holes, it's time to repot.