Lemon Balm in Zone 7B — Northern California

Lemon Balm is a fantastic addition to any Northern California garden. Its citrusy-mint flavor elevates everything from teas to salads, and its vigorous growth provides a constant supply throughout our long growing season. Plus, it's incredibly satisfying to grow your own herbs, especially in our Mediterranean climate where they thrive.

While we NorCal gardeners face challenges like drought and fire season, the extended 245-day growing season gives us plenty of time to successfully cultivate Lemon Balm. Careful watering and smart planting are key to a bountiful harvest, and the timing outlined below will set you up for success.

Starting Lemon Balm indoors gives you a head start, especially if you want a larger plant ready to go as soon as the weather warms up. Aim to sow seeds indoors from late January through mid February, about six weeks before you plan to transplant. This takes advantage of our early spring-like conditions.

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. Keep the soil consistently moist by bottom watering; set the tray in a shallow dish of water until the surface of the soil is damp.

Transplant your Lemon Balm seedlings outdoors from mid March through mid April, after the danger of any late frosts has passed. Remember to harden off your seedlings for about a week before transplanting. Gradually expose them to outdoor conditions for increasing amounts of time each day.

When transplanting, space the plants about 18-24 inches apart to allow for their bushy growth habit. Even though our springs tend to be mild, keep an eye on the forecast for any unexpected cold snaps and be prepared to cover your young plants if needed.

Direct sowing Lemon Balm is a simple and effective method, especially given our long growing season. Sow seeds directly into the garden from mid March through late August. You have a pretty wide window, so don't stress too much about exact timing.

Prepare the soil by loosening it and removing any weeds. Lemon Balm prefers well-drained soil. Keep the soil consistently moist until the seedlings emerge. Once they're up, thin them to 18-24 inches apart. Direct sowing is easy, but the plants will take a bit longer to mature compared to transplants.

Lemon Balm appreciates consistent moisture, but it's not a fan of soggy soil. In our dry Northern California climate, especially during the summer, you'll need to pay attention to its watering needs. A little neglect can lead to bolting.

During the cooler spring and fall months, water deeply about once a week, or when the top two inches of soil feel dry to the touch – use the finger test! In the hotter summer months, increase watering to two or three times a week, providing about 1 inch of water each time. Water at the base of the plant to avoid wetting the foliage, as this can encourage fungal diseases in our microclimates, even with low humidity.

Signs of underwatering include wilting or yellowing leaves. Overwatering can lead to root rot, indicated by droopy, brown leaves. A layer of mulch around the base of the plant helps retain moisture in our dry climate and reduces the need for frequent watering.

Lemon Balm requires minimal pruning but benefits from a little attention to keep it productive and prevent it from taking over your garden. In midsummer, cut the plant back by about half to encourage new growth and prevent it from becoming leggy.

Regularly remove flower stalks as they appear. This prevents the plant from self-seeding aggressively, which it's known for doing. As the first frost approaches around mid- November, you can give the plant a final trim, but leave some growth to help it overwinter. It's hardy enough to survive our mild winters and will bounce back in the spring.

You can start harvesting Lemon Balm leaves as soon as the plant is big enough, usually from late May through late November. The leaves have the best flavor before the plant flowers, so harvest frequently to encourage continued leaf production.

To harvest, simply snip off the top few inches of the stems, taking care not to remove more than a third of the plant at any one time. This encourages bushier growth. Lemon Balm is best used fresh, as it loses much of its flavor when dried. As the end of the season approaches and the first frost looms, harvest as much as you can and use it to make teas, tinctures, or other culinary creations.

Lemon Balm is generally easy to grow, but here are a few common issues Northern California gardeners might encounter:

Aggressive Spreading

• What it looks like: Lemon Balm popping up in unexpected places throughout your garden.
• What causes it: Lemon Balm spreads readily through seeds and rhizomes (underground stems). In our mild climate, it can easily become invasive if not managed.
• How to fix/prevent it: Remove flower stalks before they set seed. Consider growing Lemon Balm in a container to restrict its spread. Regularly pull up any 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 often triggered by heat, long days, or drought stress. While Lemon Balm isn't as prone to bolting as some cool-season crops, our hot summers can still cause it to bolt.
• How to fix/prevent it: Provide afternoon shade during the hottest part of the day. Keep the soil consistently moist. Harvest frequently to encourage leaf production and delay flowering.

Powdery Mildew

• What it looks like: A white or grayish powdery coating on the leaves and stems.
• What causes it: Powdery mildew is caused by various fungi that thrive in warm days, cool nights, and moderate humidity. Although our humidity is generally low, microclimates within your garden can create favorable conditions for powdery mildew.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning as needed. Remove affected leaves promptly. Apply neem oil or potassium bicarbonate sprays.

Northern California Specific Challenges: Our moderate-to-hot summers and dry conditions mean that Lemon Balm needs consistent watering to prevent bolting and stress. While low humidity helps reduce some fungal issues, powdery mildew can still occur, especially in shaded areas. Be vigilant about watering and provide afternoon shade to keep your Lemon Balm healthy and productive throughout our long growing season.

Lemon Balm is a beneficial companion plant for several vegetables in the Northern California garden. It repels certain pests and attracts pollinators.

Good companions:

• Tomatoes: Lemon Balm repels tomato hornworms and whiteflies.
• Squash: It deters squash bugs and vine borers.
• Broccoli and Cauliflower: Lemon Balm can help repel cabbage moths, which can devastate these crops.

Avoid planting Lemon Balm near anything that might suffer from its aggressive spreading. There aren't any particularly bad companions in terms of direct harm, but you want to give other plants enough space to thrive without being crowded out.