Calendula in Zone 8B — Desert Southwest

Calendula is a fantastic addition to any Desert Southwest garden. The cheerful blooms add a pop of color, and the edible petals bring a unique flavor to salads and other dishes. Plus, the plant's medicinal properties make it a worthwhile addition to your herbal garden.

Our extreme heat and alkaline soil can be challenging, but with proper timing and care, Calendula thrives here. With our long 279-day growing season, you can enjoy its beauty and benefits for months.

Starting Calendula indoors is possible, but not always necessary in our climate. If you want a head start, begin your seeds indoors from late December through mid January, about six weeks before our last expected frost.

Use seed trays with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light – a grow light works great. Don't forget to water from the bottom to encourage strong root growth and prevent damping off. Our very-early spring character means you'll want those seedlings ready to go as soon as the weather cooperates.

Transplant your Calendula seedlings outdoors from mid February through late March. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week.

Space them 8-12 inches apart in well-draining soil. Keep an eye on the weather, especially for late frosts, which can still happen during this time. Protect your young plants with frost cloth if needed.

Direct sowing Calendula is a simple and effective method in the Desert Southwest. You can sow seeds directly into the garden from mid February through early October.

Prepare the soil by loosening it and removing any rocks or debris. Calendula prefers soil temperatures around 65-70°F for optimal germination. Sow seeds 1/4 inch deep and space them 8-12 inches apart. Keep the soil consistently moist until the seedlings emerge.

Watering Calendula correctly is crucial for its survival in our arid climate. While it needs moderate water, it's not drought-tolerant, and our extreme heat can quickly stress the plant.

During the cooler months of spring and fall, water deeply once or twice a week. Use the "finger test" – if the top 2 inches of soil feel dry, it's time to water. Aim for about 1 inch of water per week. During our monsoon season, you may need to reduce watering depending on rainfall.

In the peak of summer, Calendula may go dormant. Reduce watering slightly, but don't let the soil dry out completely. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our humid monsoon season.

Signs of underwatering include wilting and dry, crispy leaves. Overwatering can lead to yellowing leaves and root rot. Mulching around the base of the plant with organic matter helps retain moisture and regulate soil temperature.

Regular pruning, specifically deadheading, will keep your Calendula plants blooming throughout the season. Remove spent flowers as soon as they start to fade to encourage the plant to produce more blooms.

Simply pinch or cut off the flower heads just below the base of the flower. At the end of the season, around our first frost in early December, you can leave some flowers to mature and self-seed for the following year.

You can expect your first Calendula harvest about 45 days after planting, typically from late March through early December in our region. Harvest the flowers when they are fully open and the petals are vibrant.

Gently pinch or cut the flower heads from the stem. Harvest in the morning after the dew has dried for the best flavor and medicinal properties. To encourage continuous production, harvest regularly and don't let the flowers go to seed unless you want them to self-sow.

As the first frost approaches in early December, harvest all remaining flowers. You can dry them for later use in teas, salves, or culinary creations.

Here are some common problems you might encounter growing Calendula in the Desert Southwest:

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves and stems. Leaves may curl, yellow, and eventually die.
• What causes it: Fungi that thrive in warm days, cool nights, and moderate humidity. Ironically, dry leaf surfaces actually favor it, which is common in our arid climate.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help. A milk spray (1 part milk to 9 parts water) is also effective.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. Sticky honeydew residue and curled or distorted new growth.
• What causes it: Rapidly reproducing sap-sucking insects. Populations can explode in our warm spring weather. Ants may farm them for honeydew.
• How to fix/prevent it: Knock them off with a strong spray of water. Encourage natural predators like ladybugs and lacewings. Use insecticidal soap for heavy infestations. Neem oil also works systemically. Avoid excess nitrogen fertilizer.

Whiteflies

• What it looks like: Tiny white, moth-like insects that fly up when disturbed. Yellowing or stippled leaves. Sticky honeydew residue.
• What causes it: Sap-sucking insects that thrive in warm, dry conditions, making them a common pest in our Desert Southwest gardens.
• How to fix/prevent it: Use yellow sticky traps to capture adults. Spray plants with insecticidal soap or neem oil, paying attention to the undersides of leaves. Encourage natural predators like lacewings and parasitic wasps.

Desert Southwest Specific Challenges: Our extreme heat and arid humidity can stress Calendula, making it more susceptible to pests and diseases. The monsoon season can bring periods of high humidity, which can exacerbate fungal problems like powdery mildew. Alkaline soil can also be an issue, so amend your soil with compost before planting.

Calendula makes a wonderful companion plant in the Desert Southwest garden. It attracts beneficial insects and can help deter pests from other plants.

Good companions include tomatoes, peppers, and green beans. Calendula repels tomato hornworms and other pests that attack tomatoes. It also attracts pollinators, which benefit peppers. Planting Calendula near green beans can help deter bean beetles.

Avoid planting Calendula near plants that are susceptible to powdery mildew, as it can spread the disease. Otherwise, Calendula is a versatile and beneficial companion for many garden vegetables.