Lemon Balm in Zone 9A — Southern California

Lemon Balm is a fantastic addition to any Southern California garden. Its bright, lemony flavor adds a refreshing zest to teas, salads, and even desserts, and it's incredibly versatile in the kitchen. Plus, it's just plain satisfying to step outside and harvest fresh herbs year-round in our mild climate.

Sure, we have our challenges here in SoCal – drought, occasional heat waves inland, and the Santa Anas can be tough on plants. But with a little planning, especially given our long 322-day growing season, you can easily grow Lemon Balm successfully.

Starting Lemon Balm indoors here in Southern California is definitely an option, but it's not strictly necessary given our long growing season. If you want a head start, though, aim to sow your seeds indoors from mid-December through early January, about six weeks before you plan to transplant outdoors.

Use seed trays filled with a good seed-starting mix. Keep them warm (a heat mat helps) and provide plenty of light – a grow light is ideal. Don't forget to water from the bottom to avoid damping off! Since spring comes very early here, this can give you a jump on the growing season.

Transplant your Lemon Balm seedlings outdoors between early February and early March. This gives them plenty of time to get established before the summer heat inland kicks in.

Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. Plant them 18-24 inches apart in a spot that gets full sun to partial shade. Even in early spring, keep an eye on the forecast for any unexpected late cold snaps.

Direct sowing Lemon Balm is easy in Southern California thanks to our mild winters and long growing season. You can sow seeds directly into the garden from early February through late September.

Prepare the soil by loosening it and removing any weeds. Lemon Balm prefers well-draining soil. Keep the soil consistently moist until the seedlings emerge. Thin them to 18-24 inches apart once they're a few inches tall.

Lemon Balm enjoys moderate watering, especially here in Southern California where we're often dealing with drought conditions and water restrictions. While it's not as drought-tolerant as some other herbs, it does tolerate more moisture than, say, rosemary.

During the cooler months, from late fall through early spring, water deeply but less frequently – maybe once a week, depending on rainfall. In the hotter summer months, especially if you're inland, you'll likely need to water two to three times a week. The best way to tell is to use the "finger test": stick your finger about 2 inches into the soil; if it feels dry, it's time to water. Aim for about 1 inch of water per week.

Water at the base of the plant to avoid wetting the leaves, which can encourage fungal diseases. Yellowing leaves can indicate overwatering, while wilting signals underwatering. Mulching around your Lemon Balm plants with compost or wood chips will help retain moisture and suppress weeds.

Lemon Balm is a pretty low-maintenance herb, but a little pruning goes a long way. In midsummer, when the plant is at its peak, cut it back by about half to prevent it from getting leggy and encourage bushier growth.

Throughout the growing season, remove any flower stalks as soon as you see them. This prevents the plant from self-seeding aggressively and keeps the leaves producing. As the first frost approaches around mid- December, you can give the plant a final light trim to tidy it up.

You can expect your first harvest of Lemon Balm leaves around mid-April if you started early, and continue harvesting all the way through late December in our Zone 9A climate. The best flavor comes from the leaves before the plant flowers, so keep an eye out for those flower stalks and remove them.

To harvest, simply snip off the stems with leaves as needed. Don't take more than a 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 weather cools in late fall, continue harvesting until the first frost.

Here are three common problems you might encounter growing Lemon Balm in Southern California:

Aggressive Spreading

• What it looks like: Lemon Balm sends out runners and pops up in unexpected places in your garden.
• What causes it: It's just naturally enthusiastic! It thrives in our long growing season and can easily spread if left unchecked.
• How to fix/prevent it: Plant Lemon Balm in a container to restrict its roots. Regularly remove any unwanted shoots that pop up.

Bolting

• What it looks like: The plant sends up a flower stalk prematurely, and the leaves become bitter or tough.
• What causes it: Bolting can be triggered by heat stress, which is definitely a concern during our summer heat inland.
• How to fix/prevent it: Provide some afternoon shade during the hottest months. Keep the soil consistently moist. Remove flower stalks as soon as you see them.

Powdery Mildew

• What it looks like: White or grayish powdery coating on the leaves and stems.
• What causes it: Powdery mildew thrives in warm days, cool nights, and moderate humidity. Although we have low-to-moderate humidity, it can still be a problem, especially in shaded areas with poor air circulation.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning. Remove affected leaves. Treat with neem oil or a milk spray (1 part milk to 9 parts water).

Southern California Specific Challenges: Our hot, dry summers and occasional Santa Ana winds can stress Lemon Balm, making it more susceptible to bolting and powdery mildew. Consistent watering and providing some afternoon shade can help mitigate these issues.

Lemon Balm makes a great companion plant in your Southern California garden. It's said to repel certain pests and attract beneficial insects.

Good companions include tomatoes, squash, broccoli, and cauliflower. Lemon Balm may help deter tomato hornworms and squash bugs. It can also attract pollinators that benefit broccoli and cauliflower.

I don't recommend planting it near anything that needs very dry soil since it prefers moderate moisture.