Peppermint (Mentha piperita) is a potent and aromatic herb utilized in companion planting due to its high concentration of volatile oils. By strategically placing this herb, gardeners can leverage its natural properties to create a more balanced and productive ecosystem. The goal is to maximize the benefits of peppermint’s strong scent and chemical profile while carefully managing its vigorous growth habits.
Understanding Peppermint’s Growth Habits and Function
Peppermint is a hybrid plant with a strong, aggressive growth pattern, spreading primarily through underground stems called rhizomes. These rhizomes quickly colonize garden beds and outcompete neighboring plants for water and nutrients. Containment is mandatory, typically achieved by planting peppermint in pots or containers. If planting directly into the ground, install a physical barrier, such as deep plastic or metal edging, 10 to 12 inches deep to block the horizontal spread.
The herb’s value as a companion lies in its elevated content of essential oils, especially menthol, which provides a strong, distinctive aroma. This potent scent acts as a natural deterrent, confusing or repelling many common garden pests. The chemical compounds released by the plant essentially mask the scent of nearby crops, making it difficult for pests to locate their preferred food source. Peppermint also attracts beneficial insects, such as hoverflies and predatory wasps, which help control pest populations.
Specific Plants That Benefit From Peppermint
Many garden vegetables and ornamental plants benefit from the presence of contained peppermint, primarily through pest deterrence. Members of the Brassica family, including cabbage, broccoli, and cauliflower, are vulnerable to the cabbage moth and flea beetle. Placing peppermint nearby helps repel the adult moths and beetles, which lay eggs that hatch into leaf-eating larvae. The strong aroma disrupts the pests’ ability to target these crops.
Tomato plants also thrive when situated near peppermint, as the minty scent helps keep away common pests like aphids and spider mites. Similarly, the foliage of roses, which are frequently attacked by aphids, can be protected by the proximity of peppermint. Peppermint is also a known repellent for the carrot fly, making it an excellent companion for carrots, and it helps deter slugs from attacking lettuce. Its presence can also benefit legumes like peas and beans by helping to ward off mice, rats, and the bean beetle.
Plants That Should Not Be Paired With Peppermint
Peppermint should be kept separate from several plants due to aggressive root competition and allelopathy. Allelopathy occurs when a plant releases biochemicals into the soil that inhibit the growth of nearby species. Peppermint is allelopathic, meaning it actively suppresses the growth of sensitive neighbors.
Delicate herbs requiring different growing conditions are particularly susceptible, even if the peppermint is contained. Drought-loving herbs, such as rosemary and lavender, are incompatible because peppermint requires consistently moist soil, which is detrimental to their health. Most other herbs, including chamomile and basil, also suffer due to root competition and allelopathic effects.
Root vegetables, such as potatoes and parsnips, should not be planted near peppermint, as they are easily overwhelmed by root encroachment. Their growth can be stunted due to the plant’s aggressive nature and the chemical compounds it releases. Even when contained, peppermint should not be sunk into the ground, as rhizomes can escape through drainage holes and invade the surrounding soil. The safest placement is in an elevated container placed on an impermeable surface, away from sensitive plants.