Lemon balm (Melissa officinalis) is a well-known herb cherished for its bright, lemony scent. This member of the mint family is commonly found in gardens. While its fragrance is appealing, lemon balm can quickly become an unwelcome presence, spreading aggressively and taking over garden spaces.
Understanding Lemon Balm’s Growth Habits
Lemon balm’s persistent nature stems from its ability to spread through underground rhizomes, which are creeping root systems that send up new shoots. These runners allow the plant to colonize large areas rapidly.
Beyond its root spread, lemon balm is also a prolific self-seeder. The plant produces numerous small flowers that, if left unchecked, generate a multitude of seeds. These seeds readily germinate, establishing new plants. Lemon balm can also regrow from small root fragments left in the soil or from dispersed seeds.
Non-Chemical Removal Strategies
Manual digging and pulling offer an effective, albeit labor-intensive, approach. Loosen the soil around the plant to remove as many roots and runners as possible. Consistent effort is necessary, as lemon balm can regrow from small root pieces.
Smothering or solarization are alternative non-chemical methods that deprive the plant of light and moisture. Covering the affected area with materials like cardboard, newspaper, or black plastic sheeting can suppress growth. This process works by cooking or smothering the plants underneath, and it is most effective during hot, sunny weather.
Regular mowing or trimming can help manage lemon balm by preventing seed production. Cutting the plant back consistently before it flowers weakens it over time and reduces the spread of new plants from seeds. While this practice can keep the plant in check, it is generally not sufficient for complete eradication on its own.
Boiling water and vinegar are sometimes suggested for localized control, but they should be used with caution. Boiling water can instantly kill plant tissue on contact, while vinegar acts as a non-selective herbicide by drying out foliage. These methods are most effective on small, isolated patches and can harm surrounding desired plants. They have limited impact on established root systems or widespread infestations.
Chemical Control Options
Chemical control options are available for severe infestations or when non-chemical methods are impractical. Non-selective herbicides, such as those containing glyphosate, kill any plant they contact.
Always read and strictly follow product label instructions. Proper application techniques, including wearing appropriate safety gear and avoiding spray drift, are necessary to prevent harm to desired plants and the environment. Chemical solutions carry environmental concerns, making them a less preferred option for many gardeners.
Preventing Recurrence
Preventing lemon balm from returning requires ongoing vigilance. Regularly monitor the area for new seedlings or sprouts emerging from lingering root fragments. Promptly remove these new growths before they establish.
Applying a thick layer of mulch can suppress new growth and inhibit seed germination. An organic mulch, at least 3 inches thick, creates a barrier that discourages lemon balm from sprouting.
Installing physical barriers around garden beds can restrict the spread of rhizomes. Burying edging material several inches underground creates a physical boundary that lemon balm roots find difficult to penetrate.
For those who still desire to grow lemon balm, cultivating it in containers is an effective way to prevent its spread. This isolates the plant’s root system and limits seed dispersal. When disposing of removed plant material, avoid composting it unless your compost system reaches high temperatures to destroy seeds and root fragments.