Lemon Balm in Zone 4B — Midwest

Lemon Balm is a fantastic herb to grow in the Midwest, adding a bright, lemony flavor to teas, salads, and even desserts. It's incredibly versatile in the kitchen, and there's a real satisfaction in harvesting your own fresh herbs from your garden. Plus, it thrives in our fertile soil and enjoys the summer heat.

Our Midwest weather can be a bit unpredictable, with temperature swings in the spring and the occasional summer heat spell. But with a little planning and attention to timing, you can easily grow Lemon Balm within our 138-day growing season. It's all about working with Mother Nature here.

Starting Lemon Balm indoors isn't strictly necessary, but it can give you a head start, especially if you're eager for an early harvest. Sow seeds indoors from late March through mid April, about six weeks before you plan to transplant. 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 is your friend when starting seeds indoors. Just set the tray in a shallow dish of water and let the soil soak it up from the bottom. This prevents damping off and keeps the seedlings happy. Given our moderate-to-late springs here in the Midwest, starting indoors buys you some time and protects your young plants from any late frosts.

Once the danger of frost has passed – usually around early May through early June – and your seedlings have a few sets of true leaves, it's time to transplant them outdoors. Before planting directly into the garden, harden them off by gradually exposing them to outdoor conditions for about a week. Start with an hour or two of shade, then slowly increase the time and sun exposure each day.

Plant your Lemon Balm seedlings 18-24 inches apart in a sunny or partially shaded spot. Keep an eye on the weather forecast, as we can sometimes get unexpected cold snaps even in May. A little row cover can protect your transplants if needed.

Direct sowing Lemon Balm is a perfectly viable option, especially if you're not in a rush for an early harvest. Wait until the soil has warmed up a bit, typically from early May through early July. Prepare the soil by loosening it and removing any weeds or debris.

Sow the seeds thinly, about ¼ inch deep, and keep the soil consistently moist until they germinate. Once the seedlings emerge, thin them to 18-24 inches apart. Direct sowing is less work than starting indoors, but keep in mind that germination can be slower, and the plants might take a little longer to mature.

Lemon Balm prefers moderate watering, and while it's not particularly drought-tolerant, it also doesn't like to sit in soggy soil. During our Midwest summers, which can swing from moderate to hot and humid, pay close attention to the soil moisture. The "finger test" is a reliable way to check: stick your finger about 2 inches deep into the soil; if it feels dry, it's time to water.

Generally, aim for about 1 inch of water per week, either from rainfall or irrigation. During hot spells, you might need to water more frequently. It's best to water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our moderate-to-humid climate.

Keep an eye out for signs of under- or overwatering. If the leaves are wilting or turning yellow, it could be a sign of underwatering. If the leaves are yellowing and the soil feels waterlogged, you're likely overwatering. Adding a layer of mulch around your Lemon Balm plants can help retain moisture in the soil and suppress weeds.

Lemon Balm is a pretty low-maintenance herb, but a little pruning can keep it looking its best. In midsummer, give the plants a haircut by cutting them back by about half. This encourages bushier growth and prevents them from getting too leggy.

Be sure to remove any flower stalks as they appear, as Lemon Balm can be quite aggressive in self-seeding. Plus, the leaves tend to lose some of their flavor once the plant starts to flower. As the first frost approaches in late September, you can give the plants one final trim to tidy them up before winter sets in.

You can start harvesting Lemon Balm leaves anytime from mid July through early October, about 70 days after planting. The leaves have the best flavor before the plant starts to flower, so keep an eye on those flower stalks! The best time to harvest is in the morning, after the dew has dried but before the sun gets too hot.

To harvest, simply snip off the leaves with scissors or pruning shears. Avoid taking more than a third of the plant at any one time, to allow it to continue growing and producing. Lemon Balm is best used fresh, as it tends to lose its flavor when dried. Harvest regularly to encourage continuous production throughout the season.

As the first frost approaches in late September, harvest any remaining leaves and use them fresh or freeze them for later use. Even if the plant dies back over winter, it will likely return in the spring, ready for another season of growth.

Here are some common problems you might encounter with Lemon Balm in the Midwest:

Aggressive Spreading

• What it looks like: Lemon Balm quickly takes over garden beds, spreading through underground rhizomes and self-seeding.
• What causes it: The plant is simply vigorous and well-suited to our Midwest climate.
• How to fix/prevent it: Plant Lemon Balm in a container to restrict its spread, or be diligent about removing unwanted seedlings. Deadhead flowers before they set seed.

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 heat, long days, or drought stress, all of which we can experience during our Midwest summers.
• How to fix/prevent it: Plant at the right time for your zone (early spring or fall). Provide shade in warm weather. Keep the soil consistently moist. Remove flower stalks as soon as you see them.

Powdery Mildew

• What it looks like: A white or grayish powdery coating appears on the leaves, stems, and sometimes fruit. Leaves curl, yellow, and die.
• What causes it: Powdery mildew thrives in warm days, cool nights, and moderate humidity, which are common conditions in the Midwest.
• 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.

Midwest Specific Challenges: Our moderate-to-hot summers, moderate-to-humid humidity, and wet-summer rainfall can create ideal conditions for powdery mildew, so good air circulation is key. Be vigilant about watering at the base of the plant to avoid wetting the foliage, and keep an eye out for any signs of disease.

Lemon Balm makes a great companion plant for several vegetables in the Midwest garden.

• Tomato: Lemon Balm repels tomato hornworms and other pests that can damage tomato plants.
• Squash: It can deter squash bugs and vine borers, which are common problems for squash in our region.
• Broccoli and Cauliflower: Lemon Balm can help repel cabbage moths and other pests that attack these brassicas.

Avoid planting Lemon Balm near other herbs that prefer drier conditions, as its moderate watering needs might not be suitable for them.