Botanically speaking, lemon balm (Melissa officinalis), which grows as a perennial in U.S. Department of Agriculture plant hardiness zones 3 through 7, and lemon mint (Monarda citriodora), an annual or tender perennial in USDA zones 5 through 9, are "kissing cousins." Both are members of the extensive mint family (Lamiaceae), but they are not related very closely. Lemon mint is one of the many species in the bee balm genus (Monarda spp.) while lemon balm and its cultivars form their own genus (Melissa spp.).
Lemon balm is a lemon-scented. sprawling herb that forms a clump up to 2 feet high and 3 feet wide, although it can be regularly clipped to a more compact form. Its crinkly, ovate foliage emerges first, followed by spiky, pale-yellow flowers from early to late summer. Gardeners prize it as a bee attractant as well as for its use in a fragrance garden and in the kitchen. Lemon balm can be used in herbal teas, as a garnish for fruit salads or to add citrus flavor notes to seafood, poultry, cheesecake and other dishes that normally pair well with lemon. Cultivars of common lemon balm include golden-leaved, variegated and lime-scented types.
One of the more compact of the bee balm group, lemon mint seldom grows taller than 30 inches or broader than 24 inches. Its shaggy-headed, pastel purple or pink flowers appear from early to late summer. Like lemon balm's leaves, lemon mint's narrow leaves produce the plant's distinctive citrus scent, which is most noticeable when it is brushed against or its leaves are crushed. Use lemon mint in the sandier or rockier sections of a fragrance garden and in a bee and butterfly garden. Lemon mint is also ideal to use in herbal teas, salads and potpourri blends.
Comparisons and Contrasts
Like a botanical Venn diagram, lemon mint and lemon balm can flourish in some of the same conditions. Both herbs grow best in either full sun or partial shade, and both can take a bit of neglect. Although lemon balm and lemon mint thrive in moderate climates, however, their full ranges of tolerance differ.
- Lemon balm can withstand cold winters yet wilts in hot climates. In contrast, lemon mint, though it typically dies in winter where it grows as an annual, sometimes returns through self-seeding or by underground runners, especially in mild climates.
- Both herbs thrive in a range of soils, but lemon balm prefers a neutral pH level of about 7.0 while lemon mint does best in chalky, lower-pH soil.
- Both lemon balm and lemon mint have the potential to become invasive. Lemon balm spreads by underground runners. Dig up the plant every few years and divide its roots, and keep its above-ground portions clipped back. Keep lemon mint or lemon balm in a container if spreading runners are a concern. Because lemon mint sometimes self-seeds, be vigilant about pulling up its seedlings adjacent to your lemon mint patch or container.