Lemon balm is a member of the mint family. It is an aromatic perennial herb easily grown in containers. A versatile plant, lemon balm is widely used as a seasoning for cooking, an ingredient for potpourri, and medicinally in teas, salves, and treatments for cold symptoms.
Lemon balm likes a bright, sunny location but tolerates shade well. It is drought tolerant when established, but is happier with moist soil. Mulch will provide protection from harsh winter weather. It also holds moisture cooling the plant in hotter or drier regions. Container grown lemon balm thrives on a patio or porch where it is protected from drying winds and midday sun. It makes an excellent indoor houseplant as well. Lemon balm grows well on a sunny windowsill or under “grow lights” of any type.
Propagate lemon balm by seed, cuttings, or division. Grown outdoors, lemon balm will propagate vegetatively with rhizomes as well as seed. Left unattended in the garden or yard, it can easily become invasive.
Lemon balm seed is small, and has a hard coat. Soak seeds overnight in warm water to soften the seed coat before planting. Sow the seeds in good quality potting soil at a depth of ¼ inch. Use a container that allows good drainage. A pot with a saucer allowing water to be wicked up from underneath and the excess drained away would be ideal. Water the seeds by misting if bottom watering is not practical. Avoid knocking the seeds out of the soil or burying them too deeply with a heavy stream of water. Keep the container in a sunny spot, the soil moist but not wet. The seeds will germinate in 12 to 21 days.
Stem cuttings taken from areas of vigorous new growth are easily rooted. Cut a four to six-inch piece from the parent plant with at least two to three nodes. Scrape around the stem at the bottom. Apply rooting hormone, tapping off any excess. Plant the cutting in fresh potting soil. Water it in well. The plant will root in two to three weeks.
Divide lemon balm in the spring or fall. If divided in the fall, allow adequate time for the new plants to become established before the first frost. If needed, move the container to an unheated garage, or bring it inside until the weather is mild. Dig up or un-pot a mature plant carefully. Shake loose soil clinging to the roots. Using hands or a sharp knife, cut the crown of the plant into sections. Woody or dead portions of the plant or its roots can be discarded. Ensure that at least three buds and a good amount of root are separated with each new plant. Carefully repot or plant the lemon balm with some fresh potting soil. Water it well to firm the soil.
Aside from regular watering, lemon balm requires little care. Fertilizer is usually unnecessary and should be used sparingly. If the container is kept outside, the lemon balm’s seed may well spread to the surrounding area with the wind. Cut or pinch off blooms before the seed matures to prevent this.