Lemon Balm in Zone 5A — Mountain West

Lemon Balm is a fantastic herb for Mountain West gardens. Its bright, lemony flavor adds a refreshing zest to teas, salads, and even desserts. Here in Zone 5A, with our intense sun and cool nights, Lemon Balm thrives, and those cool nights actually help concentrate its flavor.

Our short growing season and alkaline soil can present challenges, but with careful timing and attention to soil amendments, you can easily grow a bountiful supply of Lemon Balm. You've got roughly 138 days between frosts, which is plenty of time to enjoy this herb's benefits.

Starting Lemon Balm indoors isn't strictly necessary, but it can give you a head start on our short growing season. If you want to get a jump, 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 location with plenty of light – a sunny windowsill or under grow lights works well. Bottom watering can help prevent damping off, which is a common problem with seedlings. Remember, our spring weather is often unpredictable, so starting indoors offers some insurance against late frosts.

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

Choose a location with full sun to partial shade, spacing the plants 18-24 inches apart. Keep an eye on the weather forecast – late spring snow or hail can still happen, so be prepared to cover your young plants if needed.

Direct sowing Lemon Balm is also an option, especially if you're not looking for a head start. Sow seeds directly into the garden from early May through early July.

Prepare the soil by loosening it and removing any rocks or debris. Lemon Balm prefers well-drained soil, so amend with compost if needed. Keep the soil consistently moist until the seedlings emerge. Thin seedlings to 18-24 inches apart once they are a few inches tall. Direct sowing is easy, but remember, you're at the mercy of the weather, so be patient.

In our dry Mountain West climate, watering Lemon Balm properly is key. While it needs moderate moisture, it's not drought-tolerant. During the peak of summer, especially with our intense sun, check the soil moisture regularly.

A good rule of thumb is the "finger test": stick your finger into the soil about two inches deep. If it feels dry, it's time to water. Aim for about 1 inch of water per week, either through rainfall or irrigation. Water at the base of the plant to avoid wetting the leaves, which can increase the risk of powdery mildew, even in our low-humidity environment.

Pay attention to your plants. Wilting leaves are a sign of underwatering, while yellowing leaves could indicate overwatering. Mulching around the base of the plant with straw or wood chips helps retain moisture and regulate soil temperature, which is especially beneficial with our temperature swings.

Pruning Lemon Balm is simple and helps keep the plant healthy and productive. In midsummer, cut the plant back by about half to prevent it from becoming leggy and encourage bushier growth.

Regularly remove any flower stalks as they appear, as Lemon Balm can become quite aggressive if allowed to self-seed. Towards the end of the season, as our first frost approaches in late September, you can give the plant one final pruning 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 best flavor is just before the plant starts to flower, so keep an eye out for those flower stalks and harvest before they fully develop.

To harvest, simply snip off the leaves with scissors or your fingers. Avoid damaging the main stem. Regular harvesting encourages the plant to produce more leaves. As the first frost approaches in late September, harvest as much as you can and consider drying or freezing the leaves for later use, though the flavor is best fresh.

Here are a few common problems you might encounter with Lemon Balm in our Mountain West gardens:

Aggressive Spreading

• What it looks like: Lemon Balm popping up in unwanted areas of your garden.
• What causes it: Self-seeding and spreading roots. Lemon Balm is vigorous and can quickly take over if not contained.
• How to fix/prevent it: Remove flower stalks before they go to seed. Plant in a container or raised bed to limit spread. Dig up and divide the plant every few years to keep it under control.

Bolting

• What it looks like: The plant sends up a flower stalk prematurely. The leaves may become bitter or tough.
• What causes it: Heat stress, drought stress, or long days. Our intense sun and warm summer days can trigger bolting.
• How to fix/prevent it: Provide afternoon shade, especially during the hottest part of the summer. Keep the soil consistently moist. Harvest regularly to encourage leaf production.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves and stems. Leaves may curl, yellow, and die.
• What causes it: Fungal disease that thrives in warm days and cool nights, even with our low humidity.
• How to fix/prevent it: Improve air circulation by spacing plants properly. Remove affected leaves. Treat with neem oil or a milk spray (1 part milk to 9 parts water).

Mountain West Specific Challenges: Our intense sun can stress Lemon Balm, leading to bolting or leaf burn. Consistent watering and afternoon shade can help mitigate these issues. Also, our alkaline soil may require amendments like compost to ensure optimal growth.

Lemon Balm makes a good companion plant for several vegetables in the Mountain West garden. Plant it near tomatoes, squash, broccoli, or cauliflower.

• Tomatoes: Lemon Balm repels tomato hornworms and other pests.
• Squash: It attracts pollinators, which are essential for squash production.
• Broccoli/Cauliflower: Its strong scent can deter cabbage moths and other brassica pests.

Avoid planting Lemon Balm near rue, as it can inhibit its growth. Because Lemon Balm can be aggressive, be mindful of its placement to prevent it from crowding out its companions.