From a botanical perspective, mint plants (genus Mentha) are inherently vigorous and territorial perennials. They primarily spread through aggressive, fast-growing underground stems called rhizomes. This rhizomatic growth habit is a key survival strategy, allowing the plant to colonize an area quickly and outcompete neighboring plants for resources. When you place two different mint varieties in a single pot, you are essentially pitting their fundamental survival instincts against each other. They do not recognize each other as allies; they perceive a competitor for the finite resources within that container—namely water, nutrients, and root space.
The most significant issue with co-planting mint varieties is the high probability of one variety dominating and eventually choking out the other. The rhizomes will intertwine and compete for space underground. One variety, often the more vigorous one like peppermint (Mentha × piperita), will typically establish its root system more aggressively. Over a single growing season, it can easily overwhelm a milder variety like apple mint (Mentha suaveolens). The weaker plant will be starved of nutrients and light as the dominant mint shades it out above ground and crowds its roots below. You will likely end up with a pot that appears to contain only one mint type, as the other fades away.
Each mint variety possesses a unique chemical profile that gives it a distinct flavor and scent, such as the sharpness of peppermint, the citrus notes of orange mint (Mentha × piperita f. citrata 'Orange'), or the sweetness of spearmint (Mentha spicata). When their root systems are entangled and their stems interwoven, these volatile oils can cross-contaminate. As you brush against the leaves or harvest them, the oils from one plant can transfer to another. More subtly, some botanists suggest that the intense competition may stress the plants, potentially altering their metabolic processes and the production of these essential oils, which could dull or modify their prized unique characteristics.
While mint is generally pest-resistant, growing plants in close quarters always increases the risk of issues. A crowded pot has reduced air circulation around the stems and leaves, creating a humid microenvironment that is ideal for the development of fungal diseases like mint rust or powdery mildew. If one plant becomes infected, the proximity makes it extremely easy for the disease to spread to the other plant. Similarly, a pest infestation, such as spider mites or aphids, can jump from one stressed plant to the other much more readily than if they were isolated in separate pots.
The most successful method from the plant's point of view is to provide each mint variety with its own separate container. This respects their natural growth habit and prevents interspecies competition. By using individual pots, you ensure each plant has unimpeded access to soil, water, and nutrients, allowing it to express its full growth potential and maintain the purity of its flavor and aroma. This also makes maintenance far easier, as you can tailor care to each variety's specific needs and control its spread without having to untangle a matted web of roots from different plants.
