Lemon Balm in Zone 7A — Pacific Northwest

Lemon Balm is a fantastic addition to any Pacific Northwest garden. The lemony scent and flavor are wonderful in teas and salads, and it's incredibly satisfying to harvest fresh herbs from your own backyard, even with our mild summers and cool nights. Plus, it's a perennial, so it comes back year after year.

Our wet springs and dry summer months can present some challenges, but with a little planning, you can easily grow Lemon Balm successfully within our 183-day growing season. The timing we'll discuss will help you navigate those overcast spring days and make the most of our long, mild fall.

Starting Lemon Balm indoors is an option, especially if you're eager to get a head start. Begin in early to late March, about six weeks before you plan to transplant outdoors. This gives the seedlings a good head start before our soil warms up.

Use seed trays filled with a good seed-starting mix. Keep them consistently moist by bottom watering – set the tray in a shallow dish of water and let the soil soak it up from the bottom. Place the trays in a warm spot and under grow lights to ensure strong, healthy seedlings, because natural light can be limited during our slow PNW springs.

Transplant your Lemon Balm seedlings outdoors from mid April through mid May, once the risk of frost has passed. Be sure to harden them off first by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight we often experience in spring.

Space the plants 18-24 inches apart to allow for their mature size. Keep an eye on the weather forecast – a late cold snap can still happen, so be prepared to cover the young plants if necessary.

Direct sowing Lemon Balm is a straightforward method, especially if you're not in a rush. Sow seeds outdoors from mid April through late July. This gives you a wide window to work with, even if our spring weather is unpredictable.

Prepare the soil by loosening it and removing any weeds. Gently press the seeds into the soil, spacing them 18-24 inches apart, and keep the area consistently moist until the seedlings emerge. Direct sowing is convenient, but germination can be slower than starting indoors, especially with our cool spring soil.

Lemon Balm thrives with moderate watering, which fits well with our Pacific Northwest climate. While we have dry summer months, our overall rainfall helps keep the soil consistently moist. However, don't assume it's getting enough water just because it rained!

During the wet springs, you might not need to water at all, unless you're experiencing an unusually dry spell. Once our dry summer months arrive, check the soil moisture regularly. Use the "finger test" – stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water.

Aim for about 1 inch of water per week during the dry summer months, either from rainfall or irrigation. Water at the base of the plant to avoid wetting the leaves, which can contribute to powdery mildew in our dry-summer humidity. Yellowing leaves can indicate overwatering, while wilting leaves signal underwatering.

A layer of mulch, such as compost or bark chips, can help retain moisture and suppress weeds, which is particularly useful during our dry summer months.

Pruning Lemon Balm is simple and helps keep the plant healthy and productive. In midsummer, cut the plant back by about half to prevent it from becoming leggy and encourage fresh growth. This also helps maintain a bushier shape.

Regularly remove any flower stalks as they appear. Lemon Balm is known for aggressive self-seeding, and removing the flowers prevents it from spreading too much. Don't be afraid to harvest frequently – this also encourages new growth.

As the first frost approaches around mid- October, you can cut the plant back to a few inches above the ground. It will go dormant over the winter and return in the spring.

You can start harvesting Lemon Balm leaves as early as late June, and continue through late October. Since it matures in about 70 days, you'll have plenty of time to enjoy fresh herbs. The best flavor comes from leaves harvested before the plant flowers, so keep an eye out for those flower stalks and remove them.

To harvest, simply snip off the leaves you need. Avoid taking more than one-third of the plant at a time to ensure continued production. Lemon Balm is best used fresh, as it loses much of its flavor when dried.

As the first frost approaches in mid- October, harvest any remaining leaves you want to use. You can also make a final cut back before winter dormancy.

Lemon Balm is generally easy to grow, but here are a few common problems in the Pacific Northwest:

Aggressive Spreading

• What it looks like: Lemon Balm popping up in unwanted areas of your garden.
• What causes it: This plant spreads readily through self-seeding and underground rhizomes. Our mild climate allows it to thrive and spread quickly.
• How to fix/prevent it: Remove flower stalks before they go to seed. Consider growing Lemon Balm in a container to contain its spread. Regularly dig up and remove unwanted plants.

Bolting

• What it looks like: The plant sends up a flower stalk prematurely. Leaves become bitter or tough.
• What causes it: Bolting can be triggered by heat stress or drought. Even our mild summers can sometimes cause bolting if the plant isn't kept consistently moist.
• How to fix/prevent it: Keep the soil consistently moist. Provide shade during the hottest part of the day. Regularly remove flower stalks to encourage leaf production.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes fruit. Leaves curl, yellow, and die.
• What causes it: Powdery mildew thrives in warm days, cool nights, and moderate humidity. Our dry-summer humidity, combined with occasional overcast spring days, creates favorable conditions.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning. Remove affected leaves promptly. Apply neem oil or potassium bicarbonate sprays. Milk spray (1 part milk to 9 parts water) is also effective.

Pacific Northwest Specific Challenges: Our mild heat and dry-summer rainfall mean that Lemon Balm generally thrives here, but consistent moisture management is key to preventing bolting and powdery mildew. While late blight isn't a direct threat to Lemon Balm, maintaining good garden hygiene helps prevent its spread to other susceptible plants. Slugs can be an issue, especially with young plants, so use appropriate control methods.

Lemon Balm makes a great companion plant for several vegetables in the Pacific Northwest garden. It helps repel certain pests and attract beneficial insects.

Good companions include tomatoes and squash. Lemon Balm repels tomato hornworms and squash bugs, protecting these crops from damage. It is also good with broccoli and cauliflower, because it can deter cabbage moths.

Avoid planting Lemon Balm near rue, as it can inhibit the growth of both plants.