Lemon Balm in Zone 7A — Desert Southwest

Lemon balm is a fantastic addition to your Desert Southwest garden. Its lemony scent and flavor make it perfect for teas, salads, and even desserts. Plus, it's incredibly satisfying to grow your own herbs, especially one that thrives in our two growing seasons and tolerates some shade in the extreme heat.

While desert gardening presents unique challenges like intense sun and alkaline soil, you can easily cultivate lemon balm with the right timing and care. Our long, 230-day growing season gives you plenty of opportunities for success, even with the occasional temperature swing.

Starting lemon balm indoors gives you a head start, but it's not always essential in our climate. If you want larger plants sooner, start seeds indoors from early to late February. This gives them about six weeks to get established before transplanting.

Use seed trays with a good seed-starting mix. Keep them consistently moist by bottom watering and provide warmth and plenty of light. Remember, our spring weather can be very-early, so be ready to transplant as soon as the weather allows.

Transplant your lemon balm seedlings outdoors from late March through late April. This avoids the worst of any late frosts. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week.

Choose a spot with partial shade, especially during the hottest part of the day. Space the plants 18-24 inches apart. Keep an eye on the forecast for any unexpected temperature swings and protect your seedlings if needed.

Direct sowing lemon balm is a viable option in the Desert Southwest, especially if you're looking for a low-maintenance approach. Sow seeds from late March through mid August. This wide window takes advantage of our two growing seasons and the monsoon moisture.

Prepare the soil by loosening it and mixing in some compost. Lemon balm prefers soil temperatures around 70°F for germination. Sow seeds thinly and keep the soil consistently moist. Thin seedlings to 18-24 inches apart once they emerge. Direct sowing often results in slightly smaller plants than starting indoors, but it's a simpler method.

Lemon balm needs moderate watering to thrive in the Desert Southwest. While it can tolerate more moisture than some other herbs, it's not drought-tolerant and needs consistent attention, especially during our extreme heat.

During the spring and fall, water deeply about 2-3 times per week, providing about 1 inch of water each time. In the peak of summer, increase this to 3-4 times per week, especially if plants are in full sun. During the monsoon season, adjust your watering schedule based on rainfall. Use the finger test – if the top 2 inches of soil are dry, it's time to water.

Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases, even in our arid climate. Signs of underwatering include wilting and yellowing leaves. Overwatering can lead to root rot, indicated by limp, brown leaves. A layer of mulch around the base of the plant helps retain moisture and regulate soil temperature.

Lemon balm benefits from minimal pruning to keep it healthy and productive. In midsummer, cut the plant back by about half to prevent it from becoming leggy and encourage new growth. This is especially important in our intense summer heat.

Regularly remove flower stalks to prevent self-seeding, as lemon balm can be quite aggressive. Leave the main stems and healthy leaves intact. As the first frost approaches in early November, you can give the plant a final trim to tidy it up before winter dormancy.

You can expect your first harvest of lemon balm from early June through mid November, about 70 days after planting. The leaves are ready to harvest anytime, but they have the best flavor before the plant flowers. Look for vibrant green leaves that are free from blemishes.

To harvest, simply snip off the leaves with scissors or pinch them off with your fingers. Avoid damaging the main stem. Regular harvesting encourages continued production. As the first frost approaches in early November, harvest as much as you can and consider drying or freezing the leaves for later use, though the flavor diminishes when dried.

Lemon balm, like any plant, can face some challenges in the Desert Southwest. Here are three common issues and how to address them.

Aggressive Spreading

• What it looks like: Lemon balm spreads rapidly via underground rhizomes, popping up in unwanted areas of your garden.
• What causes it: The plant is simply very vigorous and well-suited to our growing conditions, leading it to readily expand its territory.
• How to fix/prevent it: Plant lemon balm in a container to restrict its spread, or create a physical barrier in the ground. Regularly dig up and remove any unwanted shoots that appear.

Bolting

• What it looks like: The plant sends up a flower stalk prematurely, and the leaves become bitter or tough.
• What causes it: Triggered by heat stress during our long, hot days.
• How to fix/prevent it: Plant in a location with afternoon shade to reduce heat stress. Ensure consistent watering, especially during hot spells. Regularly harvest leaves to delay bolting.

Powdery Mildew

• What it looks like: A white or grayish powdery coating appears on the leaves and stems.
• What causes it: Fungi thrive in warm days and cool nights, exacerbated by our low humidity which favors its spread on dry leaf surfaces.
• How to fix/prevent it: Improve air circulation by spacing plants appropriately and pruning. Remove affected leaves promptly. Apply neem oil or potassium bicarbonate sprays.

Desert Southwest Specific Challenges: The extreme heat and arid humidity of the Desert Southwest can stress lemon balm, making it more susceptible to bolting and powdery mildew. Providing adequate shade and consistent moisture is crucial for its survival and productivity. Monsoon moisture can create temporary humidity spikes, so monitor plants closely for signs of fungal diseases.

Lemon balm makes a good companion plant for several vegetables in the Desert Southwest garden. It benefits tomatoes and squash by repelling certain pests. It also works well with broccoli and cauliflower, as its strong scent can deter cabbage moths.

Avoid planting lemon balm near fennel, as it can inhibit its growth. Also, be mindful of its aggressive spreading habit when planting near other herbs that might be outcompeted.