Calendula in Zone 9A — Southern California

Calendula is a fantastic addition to any Southern California garden. The bright, cheerful flowers are edible, bringing a slightly peppery flavor to salads and other dishes. Plus, they attract beneficial insects and can even be used to make soothing skin salves. It's especially rewarding when you can harvest blooms nearly year-round thanks to our mild winters and long growing season!

Sure, we face challenges like drought and summer heat inland. However, with smart planting and watering strategies, you can successfully grow Calendula here. Our 322-day growing season gives you plenty of time to enjoy these beautiful and useful flowers.

Starting Calendula indoors isn't essential in Southern California, given our long growing season. However, if you want a really early start, especially if you're near the coast and experience cooler temperatures, it's an option.

You can start seeds indoors from late November through late December, about six weeks before you'd like to transplant them outdoors. Use seed trays with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light, using a grow light if needed. Bottom watering helps prevent damping off, which can be a problem with seedlings.

Transplant your Calendula seedlings outdoors from mid January through early March. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This prevents shock.

Space plants 8-12 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast. While Calendula is frost-hardy, a sudden cold snap after transplanting can still stress young plants.

Direct sowing Calendula is very easy and often the preferred method in our climate. You can 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 keep the soil consistently moist until they germinate. Thin seedlings to 8-12 inches apart. Direct sowing avoids transplant shock and is a great option if you're looking for a low-fuss gardening experience.

Calendula needs moderate watering, especially during our hot, dry summers. While somewhat drought-tolerant once established, it thrives with consistent moisture. Remember, this plant really prefers cooler weather, so proper watering is key when the summer heat inland kicks in.

During the cooler months (late fall through early spring), you might only need to water once or twice a week, depending on rainfall. Use the finger test: stick your finger about two inches into the soil. If it feels dry, it's time to water. In the heat of summer, especially inland, you might need to water every other day or even daily, providing about an inch of water each time. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our low-to-moderate humidity.

Underwatering will cause the leaves to wilt and turn yellow, while overwatering can lead to root rot. Yellowing leaves can be a sign of either extreme. A good layer of mulch, like wood chips or straw, helps retain moisture in the soil and reduce evaporation, a big help during our long dry season.

Regular deadheading is essential for keeping your Calendula plants blooming. Simply pinch or cut off spent flowers just below the flower head. This encourages the plant to produce more flowers instead of putting energy into seed production.

Throughout the growing season, remove any yellowing or dead leaves to improve air circulation and prevent disease. As the first frost approaches in mid- December, you can let some of the last flowers mature and go to seed if you want them to self-sow for the next year. Otherwise, cut the plants back to tidy them up for the winter.

You can expect your first Calendula harvest about 45 days after planting, which means early March is often the start of a long harvest season that can extend into late December. Harvest the flowers when they are fully open, ideally in the morning after the dew has dried.

Simply snip the flower heads off the plant with scissors or pruners. Continued harvesting encourages more blooms, so don't be shy! You can use the fresh petals in salads or dry them for medicinal purposes. As the weather cools in late fall, you can still harvest flowers, though they may be smaller. If you want to collect seeds, allow some flowers to dry completely on the plant, then harvest the seed heads.

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

Powdery Mildew

• What it looks like: A white or grayish powdery coating on leaves and stems. Leaves may curl, yellow, and eventually die.
• What causes it: Fungal disease that thrives in warm days, cool nights, and moderate humidity. Surprisingly, dry leaf surfaces actually favor it. This can be a problem during our temperature swings in spring and fall.
• How to fix/prevent it: Improve air circulation by spacing plants properly 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 surprisingly effective.

Aphids

• What it looks like: Clusters of tiny green, black, or white soft-bodied insects on stems and the undersides of leaves. You might also notice a sticky honeydew residue and curled or distorted new growth.
• What causes it: These sap-sucking insects reproduce rapidly, especially in warm weather. Ant colonies often "farm" them for their honeydew.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage ladybugs and lacewings, which are natural predators. Insecticidal soap is effective for heavy infestations. Neem oil can also be used. Avoid over-fertilizing with nitrogen, as this attracts them.

Whiteflies

• What it looks like: Tiny white, moth-like insects that fly up in a cloud when disturbed. Yellowing or mottled leaves. Sticky honeydew.
• What causes it: These sap-sucking insects thrive in warm, dry conditions. They can quickly become a nuisance, especially during our hot inland summers.
• How to fix/prevent it: Yellow sticky traps can help catch adult whiteflies. Spray plants with insecticidal soap, making sure to get the undersides of the leaves. Neem oil is also effective. Encourage beneficial insects like lacewings and parasitic wasps.

Southern California Specific Challenges: The combination of our hot summers inland, low-to-moderate humidity, and occasional Santa Ana winds can stress Calendula. Powdery mildew can be an issue during temperature swings. Consistent watering is crucial during the dry season, but be careful not to overwater, especially in heavy soils. Choosing a location with some afternoon shade can help protect plants from the worst of the summer heat.

Calendula makes a great companion plant in the Southern California garden.

• Tomatoes: Calendula attracts beneficial insects like ladybugs and lacewings, which prey on tomato pests like aphids and whiteflies.
• Peppers: Similar to tomatoes, Calendula helps protect peppers from common pests by attracting beneficial insects.
• Green Beans: Calendula can help deter bean beetles and other pests that attack green beans.

Avoid planting Calendula near plants that are susceptible to powdery mildew, as it can sometimes spread the disease.