Lemon Balm in Zone 6A — Pacific Northwest

Lemon Balm is a fantastic addition to any Pacific Northwest garden. Its lemony flavor brightens teas, salads, and even desserts. Plus, the satisfaction of snipping fresh herbs from your garden on a cool summer evening is hard to beat.

Our mild summers and long, cool autumns offer a decent growing window for Lemon Balm. While we might not have the blazing heat some plants crave, Lemon Balm thrives in our conditions with a little planning. With a 148-day growing season, you'll have plenty of time to enjoy your harvest.

Starting Lemon Balm indoors isn't strictly necessary in our climate, but it can give you a head start, especially if you want a larger harvest earlier in the season. Starting seeds indoors from late March through mid April, about six weeks before transplanting, is a good bet. Use seed trays with a good seed-starting mix, and provide warmth and light.

Bottom watering is a great way to keep the soil consistently moist without damping off. Because our spring days can be overcast, supplemental light might be needed. Keep an eye on the seedlings and transplant them when they have a few sets of true leaves.

Transplanting Lemon Balm outdoors should happen after the last frost, typically from early May through early June. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight.

Space your Lemon Balm plants 18-24 inches apart to give them room to grow. Keep an eye on the weather forecast; those unexpected late frosts can still sneak up on us. A layer of mulch can help retain soil moisture and regulate temperature.

Direct sowing Lemon Balm is a simple and effective method, especially if you're not in a rush. Sow seeds directly into the garden from early May through mid July. Ensure the soil is well-draining and has warmed up a bit.

Lemon Balm seeds are small, so sow them shallowly and keep the soil consistently moist until germination. Thin the seedlings to 18-24 inches apart once they're a few inches tall. Direct sowing is less work, but you might get a later harvest compared to starting indoors.

Lemon Balm prefers moderate watering, more than some of the other Mediterranean herbs we grow here. Because our summers are mild and dry, you'll need to pay attention to soil moisture. During the dry summer months, check the soil regularly.

Stick your finger about two inches deep into the soil; if it feels dry, it's time to water. Aim for about 1 inch of water per week, but adjust based on rainfall. Water at the base of the plant to avoid wetting the leaves, which can help prevent fungal issues in our dry-summer climate.

Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to yellowing leaves and root rot. A layer of mulch, like straw or wood chips, can help retain moisture and suppress weeds, which is helpful in our region where we often have long stretches between rain.

Pruning Lemon Balm is fairly straightforward. In midsummer, cut the plant back by about half to prevent it from becoming leggy. This encourages bushier growth and more flavorful leaves.

Be sure to remove any flower stalks as they appear. Lemon Balm is an aggressive self-seeder, and removing the flowers will help keep it from taking over your garden. At the end of the season, as the first frost approaches in early October, you can give the plant one last trim to tidy it up.

You can start harvesting Lemon Balm as early as mid July, and continue through mid October. The leaves are most flavorful before the plant flowers, so harvest frequently to encourage new growth. Look for healthy, vibrant green leaves as an indicator of ripeness.

To harvest, simply snip off the stems with scissors or pruners, taking care not to damage the main plant. Regular harvesting encourages continued production. As the first frost approaches in early October, harvest as much as you can and consider preserving it by making tea or infused oils, since the leaves don't dry well.

Here are some common problems you might encounter with Lemon Balm in the Pacific Northwest:

Aggressive Spreading

• What it looks like: Lemon Balm popping up in unwanted areas of your garden.
• What causes it: Lemon Balm is a vigorous self-seeder and spreads easily via underground rhizomes.
• How to fix/prevent it: Remove flower stalks before they go to seed. Consider growing Lemon Balm in a container to contain its spread. Dig up and remove unwanted plants regularly.

Bolting

• What it looks like: Plant sends up a flower stalk prematurely, leaves become bitter or tough.
• What causes it: Bolting is triggered by heat, long days, or drought stress.
• How to fix/prevent it: Provide shade during the hottest part of the day. Keep soil consistently moist. Harvest frequently to encourage leafy growth.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves and stems.
• What causes it: Fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help. Milk spray (1 part milk to 9 parts water) is surprisingly effective.

Pacific Northwest Specific Challenges: Our mild heat and dry-summer humidity can actually be beneficial for Lemon Balm, reducing the risk of some fungal diseases compared to more humid regions. However, consistent watering is key during our dry summers to prevent bolting. Keep an eye out for powdery mildew, especially in crowded plantings with poor air circulation.

Lemon Balm makes a good companion plant for several vegetables in the Pacific Northwest garden. It's said to repel certain pests and attract beneficial insects.

Good companions include tomatoes, squash, broccoli, and cauliflower. Lemon Balm may help repel tomato hornworms and squash bugs. It can also attract pollinators to help with broccoli and cauliflower production. Avoid planting Lemon Balm near anything you don't want it spreading into because it can be aggressive.