Lavender in Zone 8B — Northern California

Lavender is a no-brainer for NorCal gardens. Its fragrance is incredible, and you can use it in everything from cooking to crafts. Plus, it thrives in our Mediterranean climate, adding beauty and a touch of Provence to your yard.

We definitely have our challenges here—drought, water restrictions, the occasional smoky skies during fire season. But lavender is tough and, with a bit of planning, you can enjoy its beauty and fragrance throughout our long 269-day growing season.

Starting lavender from seed indoors is possible, but honestly, it can be a bit tricky. Unless you're a seasoned seed-starting pro, you might have better luck with established starts from a local nursery. If you're up for the challenge, though, start your seeds indoors from late December through mid January, giving them about 10 weeks before transplanting.

Use seed trays with a good seed-starting mix and provide consistent warmth and light. Bottom watering can help prevent damping off, which is a common issue with lavender seedlings. Remember, we often get some early warmth in late winter, so be prepared to keep those seedlings happy indoors until it's truly time to transplant.

Transplant your lavender outdoors from mid March through early April. Before you do, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Space your plants 12-18 inches apart to allow for good air circulation. Keep an eye on the weather forecast around transplant time. We can still get some unexpected cool snaps in early spring. Honestly, for the best results, especially if you're new to lavender, buy starts from a reputable nursery. They'll give you a head start.

Lavender is incredibly drought-tolerant, which makes it perfect for our dry summers in Northern California. The biggest mistake you can make is overwatering it. Established lavender thrives in poor, dry soil with excellent drainage.

During our mild, wet winters, you probably won't need to water at all. In the spring, give it a good soak every couple of weeks if we're not getting regular rain. Once summer hits and the temperatures rise, water deeply but infrequently – maybe once a week, or even less. Use the finger test: stick your finger about 2 inches into the soil. If it's dry, it's time to water. Aim for about 1 inch of water per week during the hottest part of summer. Always water at the base of the plant to avoid wetting the foliage, as our low humidity won't always save you from potential fungal issues.

If the leaves start to turn yellow and droop, you're likely overwatering. If the leaves look shriveled and dry, you're underwatering. A light layer of gravel mulch around the base of the plant can help improve drainage and prevent soil from splashing onto the foliage.

Pruning is essential for keeping your lavender plants healthy and productive. The key is to deadhead spent flowers and shape the plant into a nice mound.

After the main flowering period in mid-summer, prune back the stems by about one-third. Be careful not to cut into the old wood, as lavender doesn't typically regrow from there. As the first frost approaches around late November, you can do a light cleanup, removing any dead or damaged growth. The goal is to maintain the plant's shape and encourage new growth in the spring.

You can expect your first lavender harvest from mid June through late July, depending on the variety and the weather. The best time to harvest is when the flower buds are colored but not fully open. This is when they have the highest concentration of essential oils.

Cut the long stems in the morning, after the dew has dried. Use sharp pruners to avoid damaging the plant. To encourage continued production, harvest regularly throughout the flowering season. After harvesting, tie the stems into small bundles and hang them upside down in a cool, dark, and dry place to dry. As the first frost approaches in late November, harvest any remaining flower stems to dry and use.

Even lavender, as tough as it is, can have problems. In Northern California, the most common issues are root rot from overwatering, shab disease, and phytophthora.

Root Rot From Overwatering

• What it looks like: Yellowing leaves, wilting, and a general decline in the plant's health. The roots will be brown and mushy.
• What causes it: Soggy soil and poor drainage. Our Mediterranean climate means we often have periods of heavy rain followed by dry spells. Overwatering during the dry spells, or planting in poorly draining soil, can lead to root rot.
• How to fix/prevent it: Ensure your lavender is planted in well-draining soil. Amend heavy clay soils with plenty of compost and gravel. Water deeply but infrequently, and allow the soil to dry out between waterings. If you suspect root rot, carefully dig up the plant, trim away any affected roots, and replant it in a new location with better drainage.

Shab Disease

• What it looks like: Brown or black spots on the leaves and stems, often accompanied by a general decline in plant vigor.
• What causes it: A fungal infection favored by humid conditions. Although we have low humidity overall, microclimates can exist in your garden that promote this disease.
• How to fix/prevent it: Improve air circulation around the plants by spacing them properly and pruning regularly. Remove and destroy any infected plant material. Consider using a copper-based fungicide as a preventative measure, especially during periods of wet weather.

Phytophthora

• What it looks like: Sudden wilting and dieback of branches, often accompanied by a dark, water-soaked lesion at the base of the stem.
• What causes it: A soilborne pathogen that thrives in wet conditions. Similar to root rot, phytophthora is more likely to occur in poorly drained soils or areas that are consistently wet.
• How to fix/prevent it: Ensure your lavender is planted in well-draining soil. Avoid overwatering, and improve drainage by amending the soil with compost and gravel. There are no effective treatments for phytophthora once a plant is infected, so prevention is key.

Northern California Specific Challenges: Our moderate-to-hot summers, combined with low humidity and dry-summer rainfall, create an environment where lavender can thrive if given proper drainage and not overwatered. Microclimates within your garden can affect the amount of sun and moisture your plants receive, so it's important to monitor your plants closely and adjust your watering schedule accordingly.

Lavender loves company that shares its preference for well-drained soil and full sun. Rosemary, thyme, and sage are all excellent companions because they enjoy similar conditions and can even help deter pests. Roses also make great companions, as their needs align well with lavender.

Avoid planting lavender near mint. Mint is a water hog and tends to spread aggressively, potentially crowding out your lavender and creating overly moist conditions that it dislikes.