Lemon Balm

Overview. Lemon balm is a bushy, lemon-scented perennial herb in the mint family. Its crinkled, heart-shaped leaves smell of lemon when crushed, and its small creamy-white flowers bloom through summer and attract bees. Plants typically reach 1.5 to 2 feet (46 to 61 cm) tall.

This hardy perennial has naturalized in many warm and temperate areas outside its native range.

Sowing. You can start seed indoors about 4 to 6 weeks before the last spring frost. Seeds sprout in 7 to 14 days at 65 to 70 °F (18 to 21 °C). The seeds need light to germinate, so tamp them lightly into the soil and mist them rather than burying them. Seeds can be somewhat slow to germinate, so be patient.

To sow outdoors, use spring or early fall; another guide gives fall or late spring. Plant seedlings or divisions about 18 to 24 inches (46 to 61 cm) apart; another guide suggests 16 to 18 inches (41 to 46 cm). Full sun is preferred, though plants tolerate light shade.

Division is the easiest way to propagate lemon balm. Divide root pieces with three or four buds in late August or September so new growth can form before the first frost. Lemon balm can also be grown from root cuttings and stem cuttings.

Watering and feeding. Keep the soil moist but not wet, since wet soil can cause root rot. Feed lightly in spring to encourage new growth, and again after harvest.

Keeping it in check. Lemon balm can spread by seed and by rhizomes and become weedy. Growing it in a container on a patio or deck helps keep it from escaping. Pruning flower stalks before they set seed limits spreading. Cutting the plant back hard after flowering produces a fresh flush of leaves.

Pests and diseases. Watch for aphids and spider mites. Plants may be affected by powdery mildew, leaf spot, leaf blight or gray mold. Powdery mildew and root rot can follow overwatering. Sage leafhoppers may attack the plant, and verticillium wilt may rarely occur.

Harvesting. Harvest about one-third of the foliage at monthly intervals, before the plant blooms, and be careful not to bruise the leaves. Established plants can be cut two or three times in a season. New leaves are more flavorful than mature ones.

Drying and storing. Tie the stems in a bundle and hang them indoors out of direct sun to dry. Strip the dried leaves from the stems and keep them in airtight containers. Dried leaves lose much of their aroma, so fresh leaves are better. Leaves can also be frozen for later use.

For pets. Lemon balm is non-toxic to cats and dogs.

For people. The leaves and flowers are edible and are used to make tea or to flavor soups and stews.