Lavender in Zone 9A — Northern California

Growing lavender here in Northern California is incredibly rewarding. Not only do you get those fragrant, beautiful purple blooms for bouquets and crafts, but lavender thrives in our Mediterranean climate. Plus, having drought-tolerant plants in the garden is a smart move with our dry summers.

We definitely face some challenges in NorCal, especially with water restrictions and the ever-present threat of fire season. But lavender's well-suited to our long growing season, which stretches from late February all the way to early December. With a little planning, you can enjoy a thriving lavender patch.

Starting lavender from seed indoors can be a bit tricky, but it’s doable if you’re patient. If you're up for the challenge, aim to start your seeds indoors from mid-December through early January. This gives them about 10 weeks to get a head start before transplanting.

You'll need seed trays, a good seed-starting mix, and a warm, bright spot – a sunny windowsill or under grow lights works well. Bottom watering is key to avoid disturbing the tiny seeds and preventing damping off. Remember, our early spring warmth means you'll want sturdy seedlings ready to go when the time is right.

Transplanting lavender outdoors is best done from early to late March. Before you plant, be sure to harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sunlight and temperature changes.

Space your lavender plants about 12-18 inches apart to give them room to grow into their mature size. Keep an eye on the weather forecast – a late frost can still happen, so be ready to cover your young plants if needed. Honestly, given how slow lavender is from seed, you might consider buying starts from a local nursery for more reliable results.

Lavender is very drought-tolerant and thrives in the dry conditions that are typical of our Northern California summers. Overwatering is a far bigger risk than underwatering, so err on the side of dryness. Think about it – our dry summers and low humidity are perfect for this Mediterranean native.

During the hotter months, give your lavender a deep watering only when the top 2 inches of soil are dry to the touch – use the finger test! Generally, this translates to about 1 inch of water per week, delivered at the base of the plant to avoid wetting the foliage. Watch for signs of overwatering like yellowing leaves or root rot. Underwatering will show as wilting, but lavender is pretty resilient.

A light layer of gravel mulch around the base of the plant can help improve drainage and reduce soil moisture, which is particularly helpful in our sometimes unpredictable microclimates. Remember, our water restrictions mean every drop counts, so water wisely!

Pruning is essential for keeping your lavender plants healthy and productive. After the flowers fade, deadhead the spent blooms and trim back the stems, shaping the plant into a nice, rounded mound. Aim to cut back by about one-third.

The most important thing to remember is never to cut into the old, woody growth, as lavender rarely regrows from there. In late fall, before our first frost around early December, give your lavender a light trim to remove any dead or damaged growth, preparing it for the winter.

You can expect your first lavender harvest from early June through mid-July, depending on the variety and the weather. The best time to harvest is when the flower buds are showing good color but haven’t fully opened yet. This is when the fragrance is most intense.

Cut the stems long, using sharp scissors or pruning shears, ideally in the morning after the dew has dried. Bundle the stems together and hang them upside down in a cool, dark, and dry place to dry. Regular harvesting encourages more blooms throughout the season.

As fall approaches and we head towards our first frost in early December, you can harvest any remaining blooms for drying or crafting. Even if you don't harvest them all, the dried flower heads add a lovely texture to the winter garden.

Lavender is generally a low-maintenance plant, but here are a few problems to watch out for in Northern California:

Root Rot from Overwatering

• What it looks like: Yellowing leaves, wilting, and a general decline in plant health. The roots will be brown and mushy.
• What causes it: Overwatering, especially in poorly draining soil. Our dry summers can lull you into a false sense of security, but even drought-tolerant plants need well-draining soil.
• How to fix/prevent it: Ensure your lavender is planted in well-draining soil and avoid overwatering. Water deeply but infrequently, allowing the soil to dry out between waterings. Improve drainage by adding gravel or perlite to the soil.

Shab Disease

• What it looks like: Stunted growth, yellowing leaves, and brown or black spots on the stems.
• What causes it: A fungal disease that thrives in humid conditions. Although NorCal has low humidity overall, our microclimates near the coast can be more susceptible.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning to remove crowded growth. Remove and destroy any infected plant material. Fungicides may be necessary in severe cases.

Phytophthora

• What it looks like: Sudden wilting and death of the plant, often accompanied by dark lesions on the stems and roots.
• What causes it: A soilborne pathogen that attacks the roots, particularly in wet conditions. This is more common in areas with poor drainage or where irrigation is excessive.
• How to fix/prevent it: Improve soil drainage and avoid overwatering. Use disease-free plants and soil. Apply a fungicide specifically formulated for Phytophthora if necessary.

Northern California Specific Challenges: Our moderate-to-hot summers and low humidity are generally ideal for lavender, but it's crucial to manage watering carefully to prevent root rot. Be mindful of your specific microclimate, as coastal areas with morning fog may require extra attention to air circulation and drainage. And remember, even drought-tolerant plants need a little extra care during prolonged dry spells, especially with our ongoing water restrictions.

Lavender makes a wonderful companion plant for many other herbs and flowers in our Northern California gardens. Rosemary, thyme, and sage are all excellent choices. They share similar growing requirements – full sun and well-drained soil – and their aromatic foliage can help deter pests. Plus, they all thrive in our Mediterranean climate.

Roses also make great companions for lavender. The lavender can help repel aphids that often plague roses. On the other hand, avoid planting mint near lavender. Mint is a vigorous grower that can quickly outcompete lavender for resources, and its moisture requirements are very different.