Lemon Balm in Zone 7A — Mountain West

Lemon Balm is a must-have in any Mountain West garden. Its bright, lemony flavor adds a refreshing zest to teas, salads, and even desserts. The satisfaction of snipping fresh leaves on a cool summer evening, knowing they’ll enhance your next meal, is uniquely rewarding in our high-altitude climate.

Our short growing season and intense sun present challenges, but Lemon Balm is surprisingly adaptable. With proper timing and a little care, you can enjoy a bountiful harvest within our 173-day window.

Starting Lemon Balm indoors isn't essential, but it can give you a head start, especially if you want a larger harvest in the first year. Begin in early to late March, about six weeks before you plan to transplant.

Use seed trays with a good seed-starting mix. Keep the soil consistently moist (bottom watering works well to prevent damping off) and provide a warm location with plenty of light – a sunny windowsill or grow lights will do. Remember, our springs are late in the Mountains, so patience is key.

Transplant your Lemon Balm seedlings outdoors from mid April through mid May, once the risk of hard frost has passed. Before planting, harden off the seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to our intense UV and fluctuating temperatures.

Plant them 18-24 inches apart in well-drained soil. Be mindful of late-season frosts, which can still occur even in May, so be ready to cover your young plants if needed.

Direct sowing Lemon Balm is a simple and effective method, especially if you’re not in a rush. Sow seeds from mid April through mid July, once the soil has warmed up a bit.

Prepare the soil by loosening it and removing any weeds. Gently press the seeds into the soil, keeping them about 18-24 inches apart. Keep the soil consistently moist until germination. Direct sowing is easier, but transplanting gives you a jump start on the season.

Lemon Balm prefers moderate watering, but it's not drought-tolerant, so you'll need to pay attention, especially given our dry Mountain West climate. During the peak of summer, when temperatures can reach 85°F, check the soil moisture regularly.

Stick your finger about two inches deep into the soil – if it feels dry, it's time to water. Aim for about an inch of water per week, adjusting based on rainfall. Water at the base of the plant to avoid wetting the leaves, which, despite our low humidity, can still lead to fungal issues.

Signs of underwatering include wilting leaves and slow growth. Overwatering can cause yellowing leaves and root rot. Applying a layer of mulch around the base of the plant helps retain moisture and regulate soil temperature, which is important given our intense sun.

Lemon Balm requires minimal pruning, but a little attention goes a long way. In midsummer, cut the plant back by about half to prevent it from becoming leggy. This encourages bushier growth and a more abundant harvest.

Remove any flower stalks as they appear, as flowering can cause the leaves to become bitter and also encourages aggressive self-seeding. As the first frost approaches in early October, you can give the plant one final trim, but otherwise, leave it alone for the winter.

You can start harvesting Lemon Balm leaves as soon as the plant is established, typically from late June through mid October. The leaves have the best flavor before the plant flowers, so keep an eye out for those flower stalks and remove them.

To harvest, simply snip off the leaves with scissors or your fingers. Avoid taking more than one-third of the plant at any one time to ensure continued production. Lemon Balm is best used fresh, as it loses its flavor when dried. As the first frost nears in early October, harvest as much as you can and consider making Lemon Balm tea or pesto to preserve the flavor.

Here are the top three problems you might encounter with Lemon Balm in your Mountain West garden:

Aggressive Spreading

• What it looks like: Lemon Balm pops up in unwanted areas of your garden, quickly taking over.
• What causes it: Self-seeding and underground rhizomes allow it to spread rapidly.
• How to fix/prevent it: Plant in containers to restrict root spread. Remove flower stalks before they set seed. 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 is triggered by heat, long days, or drought stress, all potential issues in our Mountain climate.
• How to fix/prevent it: Provide afternoon shade during the hottest part of the day. Keep the soil consistently moist. Remove flower stalks as soon as they appear.

Powdery Mildew

• What it looks like: A white or grayish powdery coating appears on the leaves and stems.
• What causes it: Powdery mildew thrives in warm days, cool nights, and moderate humidity, conditions we can sometimes experience in our Mountain summers. Dry leaf surfaces also favor it.
• How to fix/prevent it: Improve air circulation by spacing plants adequately. Remove affected leaves. Apply neem oil or potassium bicarbonate sprays.

Mountain West Specific Challenges: Our moderate-at-altitude heat, low humidity, and dry rainfall can stress Lemon Balm, making it more susceptible to bolting and powdery mildew. Consistent watering and providing some afternoon shade are key to keeping your plants healthy and productive.

Lemon Balm makes a great companion plant for several vegetables in your Mountain West garden. Plant it near tomatoes and squash to help repel pests. It also benefits broccoli and cauliflower by attracting beneficial insects that prey on common pests.

Avoid planting Lemon Balm near herbs like rosemary or sage, as they prefer drier conditions and different soil types. Lemon Balm thrives with consistent moisture, which could negatively impact these other herbs.