Lemon Balm in Zone 4B — Great Plains

Lemon Balm is a fantastic herb to grow in our Zone 4B gardens. Its lemony scent and flavor add a bright touch to teas, salads, and even desserts. Plus, it's incredibly satisfying to harvest fresh herbs right from your backyard, especially in a region where summer produce feels like a real accomplishment.

Our short growing season and extreme weather can be challenging, but Lemon Balm is a relatively quick grower. If you time it right, you can easily get a good harvest within our 149-day growing season.

Starting Lemon Balm indoors gives you a head start, especially if you're further north in the Plains where the growing season is shorter. Starting seeds indoors from mid-March through early April, about six weeks before transplanting, is a good bet.

Use seed trays with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light – a grow light works great. Water from the bottom to avoid damping off; just set the tray in a shallow dish of water until the soil surface is moist. Be prepared for temperature swings that sometimes happen as spring gets underway.

Transplant your Lemon Balm seedlings outdoors from early May through early June, once the danger of frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week.

Space the plants 18-24 inches apart to give them room to grow. Keep an eye on the forecast; late frosts or even hail are still possible in early May, so be ready to cover your young plants if needed.

Direct sowing Lemon Balm is also an option, and it’s pretty easy. Sow seeds directly into the garden from early May through early July. The soil temperature needs to be at least 60°F for good germination.

Prepare the soil by loosening it and removing any weeds. Sow seeds about ¼ inch deep and space them 18-24 inches apart. Direct sowing works best if you have reliable rainfall or can water consistently, but keep an eye on the forecast for unexpected heat waves, which can be tough on new seedlings.

Lemon Balm needs moderate watering, so aim for consistency. Even though we often have low humidity, our hot summers mean you need to pay attention to soil moisture.

During the spring, when temperatures are cooler, water deeply once or twice a week, depending on rainfall. As the summer heat kicks in, especially in July and August, you might need to water every other day, or even daily during heat waves. Stick your finger about two inches deep into the soil; if it feels dry, it's time to water. Aim for about 1 inch of water per week.

Water at the base of the plant to avoid wetting the leaves, which can encourage fungal diseases. Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to yellowing leaves and root rot. Applying a layer of mulch around your Lemon Balm plants helps retain moisture and regulate soil temperature, which is especially helpful during our extreme temperature swings.

Pruning Lemon Balm is pretty straightforward. The main goal is to keep the plant from getting too leggy and to prevent it from taking over your garden.

In midsummer, cut the plant back by about half to encourage bushier growth. Remove any flower stalks as soon as you see them, as this will prevent the plant from self-seeding aggressively. Toward the end of the season, as the first frost approaches in early October, you can give the plant one last trim to tidy it up before winter.

You can start harvesting Lemon Balm leaves from mid-July through early October, about 70 days after planting. The leaves have the best flavor before the plant starts to flower.

Harvest leaves by snipping them off with scissors or pinching them off with your fingers. Be sure to leave at least a few inches of growth on the plant to allow it to continue producing. Harvest regularly to encourage new growth, and remember that Lemon Balm is best used fresh, as it loses its flavor when dried. As the first frost approaches, harvest as many leaves as possible and use them fresh in teas or other recipes.

Lemon Balm is generally easy to grow, but here are a few common problems we see in the Great Plains:

Aggressive Spreading

• What it looks like: Lemon Balm popping up in unwanted areas of your garden.
• What causes it: Lemon Balm spreads easily by seed and rhizomes (underground stems). It can quickly take over if left unchecked.
• How to fix/prevent it: Remove flower stalks before they set seed. Consider growing Lemon Balm in a container to limit its spread. Regularly pull up any 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: Bolting is often triggered by heat, long days, or drought stress, all of which we can experience in the Plains.
• How to fix/prevent it: Plant at the right time for your zone. Provide some afternoon shade in warm weather. Keep the soil consistently moist. Remove flower stalks as soon as you see them to encourage more leaf production.

Powdery Mildew

• What it looks like: A white or grayish powdery coating on the leaves, stems, and sometimes fruit. Leaves may curl, yellow, and die.
• What causes it: Powdery mildew thrives in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it, so it can be a problem even in our relatively dry climate.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning. Remove affected leaves. Neem oil or potassium bicarbonate sprays can help. A milk spray (1 part milk to 9 parts water) is also effective.

Great Plains Specific Challenges: Our hot summers and variable rainfall can stress Lemon Balm, making it more susceptible to bolting and powdery mildew. Consistent watering and providing some afternoon shade can help mitigate these issues. The wind can also be tough, so consider planting in a sheltered location.

Lemon Balm can be a great companion plant in your garden.

Good companions include:

• Tomatoes: Lemon Balm is said to repel tomato hornworms and other pests that bother tomatoes.
• Squash: It can help deter squash bugs and other squash pests.
• Broccoli and Cauliflower: Lemon Balm may attract beneficial insects that prey on pests that attack these brassicas.

Avoid planting Lemon Balm near anything you don't want it to spread to. Because it can be aggressive, keep it away from other herbs that might be easily overtaken, especially in our prairie soil.