Lavender in Zone 9B — Desert Southwest

Lavender is a fantastic addition to any Desert Southwest garden. Its fragrant blooms and silvery foliage thrive in our sunny climate, adding beauty and attracting pollinators. Plus, you can use it in cooking, crafts, and aromatherapy, bringing a touch of Provence to your own backyard.

Growing lavender here does present some challenges, mainly our extreme heat and alkaline soil. However, with careful planning and attention to watering, you can successfully grow lavender during our long, 313-day growing season. Timing is key to summer survival!

Starting lavender from seed indoors is possible, but it can be a slow and somewhat finicky process. If you're up for a challenge, go for it, but most Desert Southwest gardeners find it easier to buy established starter plants. If you want to start seeds, aim for early to late December, about 10 weeks before you'd like to transplant outdoors.

Use seed trays with a well-draining seed-starting mix. Provide warmth with a heat mat and plenty of light with grow lights. Bottom watering is ideal for seedlings to prevent damping off. Keep in mind that our very-early spring means starting early is key for a good head start.

Transplant your lavender seedlings outdoors from mid February through mid March, after the last expected frost. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense Desert Southwest sun.

Space your lavender plants 12-18 inches apart in a sunny spot with well-draining soil. Be prepared for temperature swings and occasional late frosts during this time. Buying starts from a local nursery is often the easiest route for reliable results.

Lavender is very drought-tolerant and thrives in the dry conditions of the Desert Southwest. Overwatering is a far greater threat than underwatering. The key is to provide just enough water to get it established and then let it do its thing.

During the cooler months of spring and fall, water deeply but infrequently, only when the top 2 inches of soil feel dry to the touch. In the extreme heat of summer, you might need to water once a week, but always check the soil first. During the monsoon season, let the rains do the work for you.

Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our arid climate. Signs of overwatering include yellowing leaves and root rot. Underwatering will cause the leaves to wilt and turn brown. Mulching with gravel or decomposed granite can help retain moisture and improve drainage.

Pruning is essential for maintaining the shape and health of your lavender plants. After the first flush of blooms in late spring or early summer, deadhead the spent flowers. This encourages more blooms and keeps the plant looking tidy.

In late summer or early fall, give the plant a more substantial prune, cutting back about one-third of the growth. Shape it into a nice mound, but be careful not to cut into the old wood, as it won't regrow. Stop pruning well before our first frost in mid- December to allow the plant to harden off for winter.

You can expect your first lavender harvest from mid May through early July, depending on the variety and the weather. The best time to harvest is in the morning, after the dew has dried but before the heat of the day sets in. 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 a few inches of foliage on the plant. Gather the stems into small bundles and tie them with twine. Hang the bundles upside down in a cool, dark, and dry place to dry. Regular harvesting encourages continued blooming throughout the season. As the first frost approaches in mid- December, harvest any remaining flowers to dry and enjoy.

Lavender can face a few challenges in the Desert Southwest, but with proper care, you can keep your plants healthy. The most common problems are:

• Root rot from overwatering
• What it looks like: Yellowing leaves, wilting, and a mushy base.
• What causes it: Soggy soil and poor drainage, exacerbated by monsoon moisture.
• How to fix/prevent it: Ensure excellent drainage, water sparingly, and avoid planting in heavy clay 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.
• How to fix/prevent it: Provide good air circulation, avoid overhead watering, and remove infected plant parts promptly.
• Phytophthora
• What it looks like: Sudden wilting, browning leaves, and dark lesions on the stems.
• What causes it: A soilborne pathogen that attacks the roots, often triggered by overwatering.
• How to fix/prevent it: Improve drainage, avoid overwatering, and use disease-free planting material.

Desert Southwest Specific Challenges: Our extreme heat can stress lavender plants, making them more susceptible to disease. The arid humidity can also create a microclimate around the plant, encouraging fungal growth. Be vigilant about watering and provide plenty of air circulation to keep your lavender thriving in our unique climate.

Companion planting can help your lavender thrive in the Desert Southwest. Rosemary, thyme, and sage are excellent companions because they share similar growing requirements: full sun, well-drained soil, and low water needs. Roses also appreciate lavender nearby, as it can help deter pests like aphids.

Avoid planting mint near lavender. Mint is a water hog and can quickly take over a garden bed, crowding out the lavender and competing for resources. Plus, mint prefers slightly more moisture than lavender can tolerate in our arid climate.