Calendula in Zone 9B — Southern California

Calendula is a fantastic flower to grow in Southern California. The bright, cheerful blooms are edible, adding a peppery kick to salads, and they have medicinal properties. Plus, they attract beneficial insects to your garden, helping control pests naturally.

While we face water restrictions and summer heat inland, Calendula's adaptability and our long growing season of 334 days make it a worthwhile addition to your SoCal garden. With careful planning, you can enjoy a continuous harvest throughout much of the year.

Starting Calendula indoors gives you a head start, especially if you want early blooms. Start seeds indoors from late November through mid December, about six weeks before you plan to transplant. This allows you to get a jump on the very-early spring character we often experience here.

Use seed trays or small pots filled with seed-starting mix. Keep the soil consistently moist by bottom watering to avoid disturbing the seeds. Place the trays in a warm location with plenty of light, such as a sunny windowsill or under grow lights.

Transplant your Calendula seedlings outdoors from mid January through late February, once they have a few sets of true leaves. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Space the plants 8-12 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather during this period, as we can sometimes experience unexpected cold snaps or late rains.

Direct sowing Calendula is easy and works well in our mild climate. Sow seeds directly into the garden from mid January through late October. This gives you a long window for succession planting and a near year-round harvest.

Prepare the soil by loosening it and removing any weeds. Sow seeds about 1/4 inch deep and 8-12 inches apart. Keep the soil consistently moist until the seedlings emerge. Direct sowing is a great low-effort option but remember that seedlings are more vulnerable to pests and weather fluctuations.

Calendula needs moderate watering to thrive, especially in our semi-arid climate. While it can tolerate some drought, consistent moisture promotes better blooms and overall plant health. Remember that Calendula prefers cooler weather and may go dormant if it gets too hot and dry.

During the cooler months (late fall, winter, and early spring), water deeply about once a week, providing about 1 inch of water. Use the finger test: stick your finger about 2 inches into the soil; if it feels dry, it's time to water. In the summer heat inland, you may need to water more frequently, perhaps every 2-3 days, especially if plants are in full sun.

Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our low-to-moderate humidity. Signs of underwatering include wilting leaves and dry soil. Overwatering can lead to root rot, indicated by yellowing leaves and soggy soil. Applying a layer of mulch around the base of the plants helps retain moisture and regulate soil temperature, which is especially helpful during our hot summers.

Pruning Calendula is essential for continuous blooming. Deadhead regularly by pinching or cutting off spent flowers just below the flower head. This encourages the plant to produce more blooms instead of setting seed.

Continue deadheading throughout the growing season, from late February through late fall. If you want Calendula to self-seed, leave some flowers to mature and dry on the plant. Towards the end of the season, around late December when the first frost is approaching, you can let the remaining flowers go to seed or pull up the plants if they are looking tired.

You can expect your first Calendula harvest about 45 days after planting, typically starting in late February and continuing through early January. Harvest the flowers when they are fully open, ideally in the morning after the dew has dried. The petals are most flavorful and have the highest medicinal properties at this stage.

To harvest, simply snip the flower heads off the plant with scissors or pruners. Be careful not to damage the surrounding foliage. Regular harvesting encourages the plant to produce more flowers, ensuring a continuous supply throughout the season.

As the end of the season approaches, you can harvest the remaining flowers before the first frost in late December. Dry the petals for later use in teas, salves, or culinary dishes. You can also collect the seeds from the dried flower heads to save for next year's planting.

Here are some common problems you might encounter growing Calendula in Southern California:

Powdery Mildew

• What it looks like: A white or grayish powdery coating on leaves, stems, and sometimes flower buds. Leaves may curl, yellow, and eventually die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor powdery mildew, unlike most fungi. This can be exacerbated by our temperature swings.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning crowded growth. Remove affected leaves promptly. Apply neem oil or potassium bicarbonate sprays. A milk spray (1 part milk to 9 parts water) can also be surprisingly effective.

Aphids

• What it looks like: Clusters of tiny, soft-bodied insects (green, black, or white) on stems and leaf undersides. You might also notice a sticky honeydew residue and curled or distorted new growth.
• What causes it: These sap-sucking insects reproduce rapidly, and populations can explode in warm weather. Ant colonies may "farm" them for their honeydew, protecting them from predators.
• How to fix/prevent it: Knock aphids off plants with a strong spray of water. Encourage natural predators like ladybugs and lacewings. Apply insecticidal soap for heavy infestations, or use neem oil. Avoid over-fertilizing with nitrogen, as this attracts aphids.

Whiteflies

• What it looks like: Tiny, white, moth-like insects that flutter around when disturbed. Yellowing or silvering of leaves. Sticky honeydew.
• What causes it: Warm weather and high humidity favor whitefly infestations. They suck sap from plants, weakening them.
• How to fix/prevent it: Hang yellow sticky traps to catch adult whiteflies. Spray plants with insecticidal soap or neem oil, paying attention to leaf undersides. Introduce natural predators like lacewings and parasitic wasps. Keep plants well-watered and fertilized to improve their resistance.

Southern California Specific Challenges: Our combination of hot summers, low-to-moderate humidity, and winter-wet rainfall can create challenges for Calendula. The summer heat inland can cause the plants to go dormant or suffer from heat stress, requiring extra watering and afternoon shade. Be vigilant about powdery mildew, especially during periods of high humidity or temperature swings. Also, Santa Ana winds can quickly dry out the soil, so monitor moisture levels carefully.

Calendula makes a great companion plant in your Southern California garden. Plant it near tomatoes and peppers to attract beneficial insects like ladybugs and lacewings, which prey on aphids and other pests that can damage these crops. Calendula also helps repel tomato hornworms.

Calendula also works well alongside green beans. Its presence can deter bean beetles and other pests that commonly attack beans. It’s generally a good idea to avoid planting Calendula near members of the cabbage family (broccoli, cabbage, kale, etc.), as they can attract cabbage moths, whose larvae will feed on these plants.