Lemon balm, or Melissa officinalis, is a fragrant herb that has been cultivated for centuries, primarily for its bright, uplifting, lemon-like scent. Lemon balm is a perennial herb. A member of the Lamiaceae family, which also includes true mints, this herb’s botanical classification is key to understanding its vigorous growth habit.
Understanding Lemon Balm’s Life Cycle
The plant’s perennial nature allows it to survive multiple growing seasons by utilizing a mechanism called overwintering. In temperate regions where temperatures regularly drop below freezing, the above-ground foliage of Melissa officinalis naturally dies back following the first hard frosts of autumn. During dormancy, the plant redirects its energy and resources downward, storing them safely in its root crown and underground root system. This protective measure allows the roots to remain alive and insulated beneath the soil surface, especially when covered with a layer of mulch. When warmer weather returns, the stored energy is used to push up new, vigorous shoots, allowing the plant to re-emerge and continue its life cycle; lemon balm is generally considered winter-hardy in USDA zones 4 through 9.
Managing Aggressive Growth in the Garden
Because lemon balm is a perennial and a relative of true mint, its ability to spread rapidly is a primary concern. While it does not typically spread by sending out the long, horizontal underground stems called rhizomes that true mints use, it still expands aggressively. The primary mechanism for its spread is self-seeding from its inconspicuous white or pale pink flowers.
Controlling this spread requires proactive management, with the most effective method being vigilant deadheading or pruning. Cutting the stems back hard immediately after flowering, and before seeds have a chance to ripen and drop, prevents a multitude of new seedlings from germinating nearby. Growing the plant in a large container is another popular and effective strategy, which completely isolates the root system and limits its clumping expansion. For in-ground planting, applying a thick layer of organic mulch around the plant’s base can help suppress the germination of any seeds that do fall.
Harvesting and Utilizing Lemon Balm
For the best flavor and potency, lemon balm leaves should be harvested when their concentration of volatile essential oils is at its peak. This ideal harvest time is typically in the morning, after the dew has dried but before the heat of the midday sun causes the oils to evaporate. It is best to collect the leaves just before the plant begins to flower, as the onset of blooming can reduce the intensity of the lemon scent and flavor.
To promote bushier growth and ensure a continuous supply of fresh leaves, harvest by cutting the stems right above a leaf node. For long-term storage, the leaves can be dried on a screen in a cool, dark place or they can be frozen. Dried lemon balm leaves are commonly used to make soothing herbal teas and infusions, while fresh leaves are excellent for flavoring culinary dishes, beverages, and potpourri.