Lavender in Zone 7B — Northern California

Lavender thrives in our Northern California Mediterranean climate, perfuming your garden with its calming scent and adding a touch of Provence to your backyard. Its fragrant flowers attract pollinators, and the drought-tolerant nature makes it a perfect choice for water-wise gardening. Plus, you can use it in countless ways, from culinary creations to homemade aromatherapy products.

We NorCal gardeners know the challenges of dry summers and potential water restrictions. But with our long growing season – around 245 days – and careful watering practices, growing lavender is definitely achievable. The timing is on your side.

Starting lavender from seed indoors is possible, but honestly, it can be a slow and challenging process. It's best suited for gardeners looking for a project or wanting a specific variety. If that's you, aim to sow seeds from mid-January through early February, about ten weeks before you plan to transplant.

Use seed trays with well-draining seed starting mix. Bottom watering is key to prevent damping off – set the tray in a shallow dish of water and let the soil absorb moisture from the bottom. Keep the trays in a warm spot, ideally with a heat mat, and provide plenty of light, especially given our early spring character.

Transplanting lavender outdoors is best done from late March through mid-April, after the last expected frost. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This will help them adjust to the sun and wind.

Space your lavender plants 12-18 inches apart in a sunny spot with well-draining soil. While our late March through mid-April weather is generally mild, be mindful of any unexpected cold snaps and protect your young plants if needed. But honestly, for reliable results, you're better off buying starts from a local nursery.

Lavender is incredibly drought-tolerant, making it ideal for our dry Northern California summers. Overwatering is its biggest enemy. The key is to let the soil dry out completely between waterings.

During our mild, wet winters, you likely won't need to water at all. As the weather warms up in spring, start checking the soil moisture regularly. Stick your finger about 2 inches deep – if it feels dry, it's time to water. During the hottest part of the summer, you might need to water once every 1-2 weeks, giving each plant about 1 inch of water. Always water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases.

Signs of overwatering include yellowing leaves and a generally droopy appearance. Underwatering will cause the leaves to wilt and turn brown. A light layer of gravel mulch around the base of the plants can help improve drainage and prevent soil from splashing onto the foliage.

Pruning is important for maintaining the shape and health of your lavender plant. After the first flush of flowers in late June through early August, deadhead the spent blooms and lightly shape the plant into a mound.

Cut back the stems by about one-third, being careful not to cut into the old, woody growth, as it won't regrow. At the end of the season, around the time of our first frost in mid-November, give your lavender a final light trim to remove any dead or damaged growth.

You can expect your first lavender harvest from late June through early August, about 90 days after transplanting. The best time to harvest is in the morning, after the dew has dried, but before the sun gets too hot.

Look for flower stems where the buds are showing good color but haven't fully opened yet. Cut the stems as long as possible, leaving several inches of foliage on the plant. Tie the stems into small bundles and hang them upside down in a cool, dark, and dry place to dry.

Harvesting regularly encourages continued blooming throughout the season. Even as our first frost approaches in mid-November, you can still harvest any remaining blooms for use in sachets or potpourri.

Here are a few common issues you might encounter with lavender in Northern California:

Root Rot from Overwatering

• What it looks like: Yellowing leaves, wilting, and stunted growth. The roots will be brown and mushy instead of white and firm.
• What causes it: Overwatering, especially in poorly draining soil. Our dry summers don't cause this, but inconsistent watering can.
• How to fix/prevent it: Ensure your lavender is planted in well-draining soil. Water deeply but infrequently, allowing the soil to dry out between waterings. Improve drainage by adding gravel to the planting hole or growing in raised beds.

Shab Disease

• What it looks like: Brown or black spots on the leaves and stems, followed by dieback of the plant.
• What causes it: A fungal disease that thrives in humid conditions. While we have low humidity, overly dense plantings can trap moisture.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning to open up the center of the plant. Remove and destroy any infected plant material. Consider a copper-based fungicide if the problem persists.

Phytophthora Root and Crown Rot

• What it looks like: Similar to root rot, but often more rapid. The plant may suddenly wilt and die.
• What causes it: A soilborne pathogen that attacks the roots and crown of the plant. Poor drainage and overwatering contribute.
• How to fix/prevent it: Ensure excellent drainage. Avoid planting lavender in areas where water tends to collect. Use disease-free potting mix. Unfortunately, once phytophthora takes hold, it's often difficult to eradicate.

Northern California Specific Challenges: Our moderate-to-hot heat and dry summers are generally ideal for lavender. However, inconsistent watering, especially during periods of water restrictions, can stress the plants and make them more susceptible to diseases. Ensure good drainage and monitor your plants closely for any signs of trouble.

Lavender is a great companion plant for many herbs and flowers in Northern California gardens. Rosemary, thyme, and sage all thrive in similar conditions – full sun and well-drained soil – and their aromatic oils can help deter pests. Roses also benefit from being planted near lavender, as lavender can help repel aphids and other rose pests.

Avoid planting mint near lavender. Mint is a vigorous grower that can quickly spread and crowd out lavender. Mint also prefers moist soil, which is the opposite of what lavender needs.