Lemon Balm in Zone 6B — Southeast

Lemon balm is a fantastic herb to grow in the Southeast. Its bright, citrusy flavor adds a refreshing touch to teas, salads, and even desserts, and it's incredibly versatile in the kitchen. Plus, there's a real satisfaction in snipping fresh herbs from your own garden, especially with our long summer growing season.

We definitely have our share of gardening challenges here in the Southeast, like humidity and fungal diseases. But with a little attention to timing and proper care, you can easily grow lemon balm. Our 208-day growing season gives you plenty of opportunity.

Starting lemon balm indoors in the Southeast isn't strictly necessary, but it can give you a head start. If you're eager to get things going, aim to sow your seeds indoors from mid-February through early March, about six weeks before you plan to transplant them outside.

Use seed trays with a good seed-starting mix, and keep them in a warm spot with plenty of light – a sunny windowsill or under grow lights works well. Bottom watering helps keep the soil consistently moist without over-wetting the leaves and encouraging fungal growth. With our moderate spring temperatures, you don't need a super-elaborate setup.

Once the danger of frost has passed – usually from early April through early May – you can transplant your lemon balm seedlings outdoors. Before planting them in the ground, harden them off by gradually exposing them to outdoor conditions for about a week.

Choose a spot with full sun to partial shade, and space the plants about 18-24 inches apart. Our weather can be unpredictable during this time, so keep an eye out for late frosts and protect your young plants if needed.

Direct sowing lemon balm is a simple and effective option in the Southeast. Wait until the soil has warmed up a bit, ideally from early April through early August.

Prepare the soil by loosening it and removing any weeds. Scatter the seeds lightly over the surface, and gently press them into the soil. Keep the soil consistently moist until the seedlings emerge. Remember to thin the seedlings to 18-24 inches apart once they're a few inches tall.

Lemon balm enjoys moderate watering, which is something to keep in mind with our often-wet Southeast summers. While it's not drought-tolerant, it tolerates more moisture than some other herbs.

During the hotter months, especially in the absence of our regular afternoon thunderstorms, check the soil moisture regularly. Stick your finger about two inches deep into the soil; if it feels dry, it's time to water. Aim for about an inch of water per week, whether from rainfall or irrigation. Water at the base of the plant rather than overhead to reduce humidity around the leaves and minimize the risk of fungal diseases.

Yellowing leaves can indicate overwatering, while wilting suggests underwatering. A layer of mulch around the base of the plant can help retain moisture and suppress weeds, but don't overdo it – you want to avoid creating a damp environment that encourages fungal problems.

Lemon balm is a pretty low-maintenance herb, but a little pruning can keep it looking its best. In midsummer, when the plant is growing vigorously, cut it back by about half to prevent it from becoming leggy and encourage bushier growth.

Also, be sure to remove any flower stalks as they appear. Lemon balm can be quite aggressive in self-seeding, and removing the flowers will help keep it from spreading too much. As the first frost approaches around late October, you can give the plant one last trim to tidy it up for the winter.

You can start harvesting lemon balm leaves as soon as the plant is big enough, usually from mid-June through early November here in the Southeast. The leaves have the best flavor before the plant starts to flower, so keep an eye out for those flower stalks and harvest before they bloom.

To harvest, simply snip off the leaves with scissors or your fingers. Try to avoid taking more than a third of the plant at any one time to allow it to continue producing. Lemon balm is best used fresh, as it loses its flavor when dried. As late October approaches, harvest as much as you can and consider making teas or tinctures to preserve the flavor.

Here are a few common problems you might encounter with lemon balm in the Southeast:

Aggressive Spreading

• What it looks like: Lemon balm popping up in unexpected places in your garden.
• What causes it: This herb is a prolific self-seeder. Once it gets established, it can spread quickly.
• How to fix/prevent it: Remove flower stalks before they go to seed. Consider growing lemon balm in a container to contain its spread.

Bolting

• What it looks like: The plant sends up a flower stalk prematurely, and the leaves become bitter or tough.
• What causes it: Bolting is often triggered by heat stress, which we certainly get plenty of in the Southeast.
• How to fix/prevent it: Plant lemon balm in a location with some afternoon shade to protect it from the hottest sun. Keep the soil consistently moist, and harvest regularly to encourage new growth.

Powdery Mildew

• What it looks like: A white or grayish powdery coating on the leaves and stems.
• What causes it: Powdery mildew thrives in warm days, cool nights, and moderate humidity.
• How to fix/prevent it: Improve air circulation by spacing your plants properly. Remove any affected leaves promptly. You can also try spraying with neem oil or a milk solution (1 part milk to 9 parts water).

Southeast Specific Challenges: Our hot, humid summers and wet-summer rainfall create ideal conditions for fungal diseases like powdery mildew. Be vigilant about monitoring your plants, and take action quickly if you spot any problems.

Lemon balm can be a great companion plant for certain vegetables in the Southeast garden.

Good companions:

• Tomatoes: Lemon balm is said to repel tomato hornworms, a common pest in our region.
• Squash: It may help deter squash bugs and vine borers.
• Broccoli and Cauliflower: The strong scent of lemon balm can confuse cabbage moths, which lay eggs that hatch into cabbage worms.

I wouldn't recommend planting it near anything that needs consistently dry soil, as lemon balm prefers moderate moisture.