Lemon Balm in Zone 7A — Northern California

Lemon Balm is a fantastic addition to any Northern California garden. Its lemony scent and flavor are perfect for teas, salads, and even adding a bright note to summer cocktails. Plus, it's incredibly satisfying to grow your own herbs in our Mediterranean climate with its long growing season.

While we face drought and occasional fire season challenges here, Lemon Balm's adaptability and relatively quick growth cycle make it a manageable and rewarding plant for your garden. You'll have plenty of time to enjoy its bounty within our generous 235-day growing season.

Starting Lemon Balm indoors isn't strictly necessary here in Northern California, but it can give you a head start, especially if you're aiming for an early harvest. Starting seeds indoors from late January through mid February, about six weeks before our typical transplant window, will give you a jump.

Use seed trays with a good seed-starting mix and keep them in a warm location with plenty of light. Bottom watering is ideal – set the tray in a shallow dish of water and let the soil soak it up to prevent damping off. With our early springs, this can be a great way to get ahead.

Transplanting your Lemon Balm seedlings outdoors should happen mid March through mid April. Before you put them in the ground, harden them off by gradually exposing them to outdoor conditions for about a week. This prevents shock.

Space your Lemon Balm plants about 18-24 inches apart to give them room to bush out. Keep an eye on the weather forecasts during this time – we can still get some unexpected cool snaps in early spring, so be prepared to cover your seedlings if needed.

Direct sowing Lemon Balm is a perfectly viable option in our climate. You can sow seeds directly into the garden from mid March through mid August. Choose a spot with well-drained soil and make sure the soil temperature is consistently above 60°F.

Prepare the soil by loosening it and mixing in some compost. Sow seeds about ¼ inch deep and keep the soil consistently moist until they germinate. Thin seedlings to 18-24 inches apart once they're a few inches tall. Direct sowing is easy, but you'll need to be diligent about watering.

Lemon Balm enjoys moderate watering, which means paying close attention to the soil moisture, especially during our dry summers. Here in Northern California, that's key. While it tolerates more moisture than some herbs, soggy soil is a no-go.

During the warmer months, water deeply about once a week, providing about 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 rather than overhead to minimize fungal issues, particularly as our days warm up.

In the cooler spring and fall months, you can usually reduce watering frequency. Overwatering can lead to root rot, while underwatering will cause the leaves to wilt and turn yellow. Mulching around the base of the plant with straw or wood chips helps retain moisture and regulate soil temperature during our fluctuating conditions.

Pruning Lemon Balm is pretty straightforward. The most important thing is to keep it from getting too leggy and to control its spread.

In midsummer, give your Lemon Balm a haircut by cutting it back by about half. This encourages bushier growth and prevents it from becoming too woody. Also, remove any flower stalks as soon as you see them to prevent self-seeding, which Lemon Balm is known for! As the first frost approaches around early November, you can cut back the plant to a few inches above the ground. It will bounce back in the spring.

You can start harvesting Lemon Balm leaves as early as late May and continue all the way through mid November, weather permitting. The leaves are at their peak flavor just before the plant starts to flower, so keep an eye out for that.

To harvest, simply snip off the stems with scissors or pruning shears, taking care not to damage the main plant. Harvesting regularly encourages new growth and keeps the plant producing. Fresh Lemon Balm is best, as it loses its flavor when dried.

As the first frost approaches in early November, you can harvest the remaining leaves and use them fresh or freeze them for later use. You can also bring a potted Lemon Balm plant indoors to enjoy throughout the winter.

Lemon Balm, while easy to grow, can present a few challenges in Northern California gardens. Here are three common issues:

Aggressive Spreading

• What it looks like: Lemon Balm pops up in areas where you didn't plant it, quickly taking over garden beds.
• What causes it: Lemon Balm spreads via seeds and rhizomes (underground stems). Our mild winters allow it to thrive and spread rapidly.
• How to fix/prevent it: Plant Lemon Balm in a container to restrict its spread. Remove flower stalks promptly to prevent seed dispersal. Dig up and remove unwanted plants regularly.

Bolting

• What it looks like: The plant sends up a flower stalk prematurely, and the leaves become bitter and less flavorful.
• What causes it: Bolting is triggered by heat, long days, or drought stress, all of which we can experience in our summers.
• How to fix/prevent it: Provide afternoon shade during the hottest part of the day. Keep the soil consistently moist. Regularly harvest leaves to encourage vegetative growth.

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 often see, especially in microclimates closer to the coast.
• How to fix/prevent it: Improve air circulation by spacing plants properly. Remove affected leaves. Apply neem oil or potassium bicarbonate sprays. A milk spray (1 part milk to 9 parts water) can also be effective.

Northern California Specific Challenges: Our moderate-to-hot summers and dry-summer rainfall patterns mean you need to be vigilant about watering to prevent bolting. The low humidity can actually favor powdery mildew, so proper spacing and air circulation are crucial. Be mindful of water restrictions and choose water-wise gardening practices to keep your Lemon Balm happy and healthy.

Lemon Balm makes a great companion plant for several garden vegetables.

• Tomato: Lemon Balm repels tomato hornworms and other pests that can damage tomato plants.
• Squash: It attracts pollinators, which are essential for squash production.
• Broccoli & Cauliflower: It helps to deter cabbage moths and other pests that target these brassicas.

Avoid planting Lemon Balm near other herbs that prefer drier conditions, as Lemon Balm likes consistently moist soil. It doesn't have any known bad companions in the vegetable garden.