Lemon Balm in Zone 5A — Northeast

Lemon balm is a fantastic herb to grow in the Northeast. Its citrusy, minty flavor brightens up teas, salads, and even desserts, and it’s incredibly versatile in the kitchen. Plus, the satisfaction of harvesting your own fresh herbs, especially with our short growing season, is hard to beat.

We Northeast gardeners are used to battling late spring frosts and early fall freezes, making the most of our 153-day growing season. But with careful timing and a little planning, you can easily enjoy a bountiful harvest of lemon balm right in your backyard.

Starting lemon balm indoors gives you a head start, especially useful with our shorter summers. You can begin sowing seeds indoors from mid-March through early April, roughly six weeks before you plan to transplant them outside. Use seed trays with a good seed-starting mix, and keep them warm and consistently moist – bottom watering is a great way to prevent damping off.

A simple setup with a grow light helps ensure strong, healthy seedlings. Our late springs mean indoor starts are key to maximizing yields of many plants.

Transplant your lemon balm seedlings outdoors in early to late May, once the danger of frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the temperature and sunlight, preventing transplant shock.

Space the plants 18-24 inches apart to allow for their mature size. Keep an eye on the weather forecast – those unexpected late frosts can still sneak in!

Direct sowing lemon balm is definitely an option, especially if you're looking for a low-maintenance approach. Sow seeds directly into the garden from early May through early July. The soil temperature should be at least 60°F for good germination.

Prepare the soil by loosening it and removing any rocks – we know all about rocky New England soil! Space the seeds 18-24 inches apart. Direct sowing is easier, but it may result in a slightly later harvest than starting indoors.

Lemon balm needs moderate watering, especially here in the Northeast. While it's not drought-tolerant, it can handle more moisture than many other herbs, and even appreciates some afternoon shade. During our moderate summers, aim to water deeply once or twice a week, providing about 1 inch of water each time.

The "finger test" is a reliable way to check soil moisture: stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. In our moderate-to-humid climate, watering at the base of the plant is preferable to overhead watering, which can encourage fungal diseases.

Watch for signs of underwatering, like wilting leaves, or overwatering, like yellowing leaves. A layer of mulch can help retain moisture and keep the soil cool, which is especially helpful during the warmer stretches of summer.

Pruning lemon balm is fairly simple. In midsummer, give the plant a good haircut, cutting it back by about half. This encourages bushier growth and prevents it from becoming leggy.

Be sure to remove any flower stalks as they appear. Lemon balm is known for aggressive self-seeding, and removing flowers helps keep it from taking over your garden. At the end of the season, after our first frost around early October, you can cut the plant back to the ground.

You can start harvesting lemon balm leaves from early July through early October, about 70 days after planting. The leaves have the best flavor before the plant starts to flower, so harvest frequently to encourage new growth. Simply snip off the stems with scissors or garden shears, taking care not to damage the main plant.

Lemon balm is best used fresh, as it tends to lose its flavor when dried. To encourage continued production, harvest regularly throughout the growing season. As our first frost approaches in early October, harvest any remaining leaves to use fresh or freeze for later use.

Lemon balm is generally easy to grow, but here are three common problems you might encounter in the Northeast:

Aggressive Spreading

• What it looks like: Lemon balm pops up in unexpected places throughout your garden.
• What causes it: It self-seeds readily and spreads via underground roots.
• How to fix/prevent it: Remove flower stalks before they go to seed. Consider growing it in a container to limit its spread. Be diligent about pulling up unwanted seedlings.

Bolting

• What it looks like: The plant sends up a flower stalk prematurely, and the leaves become bitter or tough.
• What causes it: Triggered by heat, long days, or drought stress.
• How to fix/prevent it: Plant in partial shade, especially during the hottest part of the summer. Keep the soil consistently moist. Harvest frequently to prevent the plant from flowering.

Powdery Mildew

• What it looks like: A white or grayish powdery coating on the leaves and stems.
• What causes it: Fungi that thrive in warm days, cool nights, and moderate humidity (common in the Northeast).
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning. Remove affected leaves. Apply neem oil or potassium bicarbonate sprays.

Northeast Specific Challenges: Our moderate heat, moderate-to-humid humidity, and even rainfall can create ideal conditions for powdery mildew. Regular monitoring and preventative measures are key.

Lemon balm makes a great companion plant for several vegetables. It's said to repel certain pests, benefiting tomatoes and squash. It also works well near broccoli and cauliflower, potentially deterring cabbage moths.

Avoid planting it near rue, as they are said to inhibit each other's growth. It's also worth keeping some space between lemon balm and other herbs, given its tendency to spread.