Lemon Balm in Zone 3B — Midwest

Lemon balm is a fantastic herb to grow here in the Midwest. Its citrusy, minty flavor brightens teas and dishes, and it's surprisingly versatile in the kitchen. Plus, there's a real satisfaction in harvesting your own herbs, especially when they thrive in our fertile soil and summer heat.

Our Midwest weather can be a bit unpredictable, especially in spring, and we sometimes get summer heat spells. But don't worry, with a little planning, you can easily grow lemon balm within our 118-day growing season. We'll walk you through the timing.

Starting lemon balm indoors gives you a head start, but it's honestly not essential in our zone. If you're eager to get growing, aim to start your seeds indoors in early to late April, about six weeks before you plan to transplant. This can be helpful if you are trying to get a very early harvest.

Use seed trays or small pots filled with a good seed-starting mix. Keep them consistently moist, watering from the bottom to avoid damping off. A warm spot and grow lights will ensure good germination, especially since our springs here in the Midwest can be a bit moderate-to-late.

Transplanting lemon balm outdoors should happen after the danger of frost has passed, typically mid May through mid June. Don't rush it; watch for late frost warnings!

Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. Space them 18-24 inches apart in a sunny or partially shaded spot. Keep an eye on the weather forecast – a sudden cold snap can still happen, so be ready to cover them if needed.

Direct sowing lemon balm is a simple and effective method in the Midwest. Wait until the soil has warmed up, usually mid May through late June. This gives the seeds the best chance to germinate quickly.

Prepare your garden bed by loosening the soil and removing any weeds. Sow the seeds thinly, and gently press them into the soil. Keep the soil consistently moist until they germinate. Thin seedlings to 18-24 inches apart once they're a few inches tall.

Lemon balm enjoys consistent moisture but doesn't like to be waterlogged, which is good to know with our wet summers. A good rule of thumb is to water when the top two inches of soil feel dry to the touch – the "finger test."

During our moderate-to-hot summer heat spells, aim for about an inch of water per week, either from rainfall or irrigation. Water at the base of the plant to avoid wetting the leaves, which can encourage fungal diseases in our moderate-to-humid climate.

If the leaves are wilting or turning yellow, you might be underwatering. If the leaves are yellowing and the plant seems stunted, you might be overwatering. A layer of mulch can help retain moisture and regulate soil temperature, which is especially helpful during those summer heat spells.

Lemon balm is a fairly low-maintenance plant when it comes to pruning. The main goals are to keep it from getting too leggy and to prevent it from spreading too aggressively.

In midsummer, cut the plant back by about half to encourage bushier growth. Remove any flower stalks as soon as you see them to prevent self-seeding; lemon balm can be quite invasive. As the first frost approaches around mid- September, you can give it one last trim before winter.

You can start harvesting lemon balm leaves as soon as the plant is established, usually late July through late September. The best flavor comes from leaves harvested before the plant flowers.

Simply snip off the leaves as needed, taking care not to remove more than a third of the plant at a time. This encourages continued production. As the end of the season approaches and the first frost looms, harvest as much as you can and preserve it by making tea or infused oil.

Here are some common issues you might encounter with lemon balm in the Midwest:

Aggressive Spreading

• What it looks like: Lemon balm popping up everywhere in your garden, even in places you didn't plant it.
• What causes it: Lemon balm spreads easily by seed and rhizomes, and it thrives in our fertile soil.
• 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: Bolting can be triggered by summer heat spells or drought stress.
• How to fix/prevent it: Provide some afternoon shade during the hottest part of the day. Keep the soil consistently moist. Harvest regularly to encourage leaf production.

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, all of which we experience here in the Midwest.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning. Remove affected leaves promptly. Consider a milk spray (1 part milk to 9 parts water).

Midwest Specific Challenges: Our moderate-to-hot heat and moderate-to-humid humidity can create ideal conditions for powdery mildew and bolting if you're not careful. Consistent watering and good air circulation are key to keeping your lemon balm healthy.

Lemon balm can be a great companion plant in the Midwest garden:

• Tomatoes: Lemon balm may help repel some pests that bother tomatoes, and its presence can enhance tomato growth.
• Squash: The strong scent of lemon balm can deter squash vine borers, a common pest in our region.
• Broccoli/Cauliflower: Lemon balm can help repel cabbage moths, which can wreak havoc on these brassicas.

Avoid planting lemon balm near plants that prefer very dry conditions, as lemon balm likes consistent moisture.