Lemon balm (Melissa officinalis) is a fragrant perennial herb belonging to the mint family (Lamiaceae). Characterized by its bright green, heart-shaped leaves, the plant releases a strong, refreshing lemony scent when brushed or crushed. This aromatic herb is often used in companion planting—strategically placing different species near each other to create a mutually beneficial environment that results in enhanced growth, improved flavor, or natural pest control.
Beneficial Planting Partners
Lemon balm’s strong aroma and small flowers make it a highly effective companion plant, serving as both a pollinator attractor and a natural pest repellent. The herb’s tiny, nectar-rich blossoms attract beneficial insects, particularly honeybees and native pollinators. Planting lemon balm near fruiting vegetables like squash, cucumbers, or melons encourages a higher rate of flower visitation. This increased activity leads to more successful pollination and a better harvest of fruits.
The volatile compounds in the herb’s citrusy scent, including citronellal and geranial, deter certain garden pests. This is helpful for protecting brassicas, such as broccoli, cabbage, and kale, from the cabbage white butterfly and its larvae. Interplanting lemon balm around these crops helps mask the brassicas’ odor, making it harder for pests to locate their target.
The herb also works well near tomatoes by attracting pollinators and beneficial predatory insects. Ladybugs and lacewings, drawn to the lemon balm, will move onto the tomatoes to feed on common pests like aphids, whiteflies, and mites. Planting it near root vegetables like carrots and onions helps mask their scent from pests like carrot flies and onion maggots. The herb’s aromatic barrier provides a layer of confusion, allowing the underground crops to develop.
Plants to Keep Distance From
While lemon balm offers many benefits, its vigorous nature means it does not pair well with all garden plants, particularly those sensitive to competition. The primary issue is the herb’s robust growth habit, which allows it to aggressively compete for water and soil nutrients. Delicate herbs, such as chamomile or thyme, can be overwhelmed and shaded out by lemon balm’s rapidly expanding clump.
Other herbs, including basil and sage, may struggle when planted too closely, as they prefer less moisture and different soil conditions than lemon balm. Competition for available resources in a confined garden bed can lead to stunted growth and reduced vigor in these less dominant plants. Furthermore, some research suggests that lemon balm may exhibit allelopathy, a process where a plant releases biochemicals that inhibit the growth of nearby species.
Root vegetables that require a long, undisturbed growing period, such as parsnips or demanding varieties of carrots, may suffer from having a fast-growing neighbor. The dense root system of the lemon balm competes heavily with these crops, potentially reducing the size and quality of the harvest. These nutrient-intensive and less competitive plants should be given dedicated space away from the lemon balm’s expanding territory.
Managing Lemon Balm’s Growth Habit
As a member of the mint family, lemon balm tends to spread aggressively, requiring proactive management to prevent it from overtaking neighbors. While it does not spread via underground runners like true mint, it expands into a large clump and is a prolific self-seeder. The simplest method of control is to plant the lemon balm in a container, such as a terracotta pot, and sink the pot directly into the garden soil.
The “pot-in-pot” technique provides a physical root barrier that contains the herb’s lateral spread, allowing it to remain a beneficial companion without becoming invasive. For in-ground planting, installing a root barrier made of plastic or metal sheeting sunk at least 10 to 12 inches deep is also effective. To control self-seeding, regular deadheading is necessary, which involves snipping off the small, white flowers before they drop seeds. Frequent harvesting also helps by keeping the plant bushy, delaying flowering, and reducing the overall volume of seeds produced.