Lemon Balm in Zone 4B — Mountain West

Lemon Balm is a fantastic herb to grow here in the Mountain West. Its bright, lemony flavor adds a delicious zest to teas, salads, and even desserts. Plus, it's incredibly satisfying to harvest your own herbs in our short growing season, bringing fresh flavors right to your kitchen.

Our high altitude and intense sun can be a challenge, and our growing season is short at just 128 days. But with careful timing and a little planning, you can absolutely enjoy a thriving Lemon Balm patch. We'll cover everything you need to know to succeed.

Starting Lemon Balm indoors is definitely an option here in the Mountain West, especially if you want a head start on the season. You have about a 3-week window from late March through mid April to get those seeds going indoors. This gives you about 6 weeks to nurture seedlings before our typical transplant window.

Use seed trays or small pots with a good seed-starting mix. Keep the soil consistently moist, and consider bottom watering to avoid damping off. A warm location and grow lights will help ensure strong, healthy seedlings. Remember, spring can be slow to arrive in the Mountains, so starting indoors gives your Lemon Balm a fighting chance.

Transplanting Lemon Balm outdoors can happen from mid May through mid June, once the risk of frost has passed. Before you move your seedlings outside permanently, be sure to harden them off. This means gradually exposing them to outdoor conditions for about a week.

Choose a location with full sun to partial shade, and space your plants 18-24 inches apart. Even in late spring, we can get some wild temperature swings, so be prepared to cover young transplants if a cold snap threatens.

Direct sowing Lemon Balm is also a viable option. You can sow seeds directly into the garden from mid May through late June. The advantage to direct sowing is not having to harden off seedlings.

Make sure the soil is well-prepared and has warmed up a bit. Lemon Balm needs a soil temperature of at least 60°F to germinate well. Sow seeds about 1/4 inch deep and keep the soil consistently moist until they sprout. Thin seedlings to 18-24 inches apart.

Lemon Balm needs moderate watering, especially here in our dry Mountain climate. While it tolerates more moisture than some other herbs, it's definitely not drought-tolerant. Finding that sweet spot is key.

During our short growing season, water deeply about once a week, providing roughly 1 inch of water. Use the "finger test" – stick your finger about 2 inches into the soil. If it feels dry, it's time to water. Water at the base of the plant to avoid wetting the leaves, which can lead to problems even with our low humidity.

In the hottest part of the summer (if we get those 85°F days), you might need to water twice a week. Look for signs of underwatering, like wilting leaves, or overwatering, like yellowing leaves. A light layer of mulch around the base of the plant can help retain moisture in our dry air.

Pruning Lemon Balm is simple, but important for maintaining a healthy and productive plant. In midsummer, cut the plant back by about half to prevent it from getting leggy and overgrown. This encourages bushier growth and more flavorful leaves.

Be sure to remove any flower stalks as soon as they appear. Lemon Balm is an aggressive self-seeder, and removing flowers will prevent it from taking over your garden. As the first frost approaches in mid- September, you can give the plant a final trim to tidy it up for winter.

You can start harvesting Lemon Balm leaves anytime from late July through late September, about 70 days after planting. The leaves have the best flavor before the plant starts to flower, so keep an eye out for those flower stalks!

To harvest, simply snip off the stems with leaves as needed. Avoid taking more than one-third of the plant at a time to ensure continued production. Lemon Balm is best used fresh, as it loses much of its flavor when dried. As the first frost approaches in mid- September, harvest as much as you can and preserve it by making teas or tinctures.

Here are three common problems you might encounter with Lemon Balm in the Mountain West:

Aggressive Spreading

• What it looks like: Lemon Balm popping up in unwanted areas of your garden, far from the original planting site.
• What causes it: Lemon Balm is a vigorous self-seeder and spreads easily via rhizomes (underground stems).
• How to fix/prevent it: Remove flower stalks before they go to seed. Plant in a container or raised bed to contain its spread. Dig up and remove unwanted plants promptly.

Bolting

• What it looks like: The plant sends up a flower stalk prematurely. Leaves become bitter and less flavorful.
• What causes it: Bolting is often triggered by heat stress, drought stress, or long days. Even though our summers aren't super hot, the intense sun can still cause bolting.
• How to fix/prevent it: Provide afternoon shade, especially during the hottest part of the summer. Keep the soil consistently moist. Harvest leaves frequently to encourage continued 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. While our humidity is low, the cool nights we experience can still create favorable conditions.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning. Remove affected leaves promptly. Apply neem oil or potassium bicarbonate spray.

Mountain West Specific Challenges: Our intense sun can lead to bolting, so providing some afternoon shade is beneficial. Even with low humidity, powdery mildew can still be an issue due to cool nights, so good air circulation is key. Also, be vigilant about controlling its spread, as it can quickly take over your garden in our short growing season.

Lemon Balm makes a great companion plant for several vegetables. It's said to repel certain pests, which can benefit your tomatoes, squash, broccoli, and cauliflower. These plants all enjoy similar sun and water conditions, making them good garden neighbors.

Avoid planting Lemon Balm near rue, as it can inhibit its growth. Because Lemon Balm is so aggressive, it's best to avoid planting it near delicate or slow-growing herbs that might get crowded out.