Calendula in Zone 3A — Great Plains

Calendula is a fantastic addition to any Great Plains garden. The bright, cheerful flowers are edible, adding a peppery zest to salads, and they have medicinal properties too. Plus, they attract pollinators to your garden, which is always a win in our climate with its intense sunshine and need for every advantage we can get.

Our extreme weather and short growing season here in Zone 3A can be challenging, but Calendula's relatively quick maturity makes it a great choice. With a little planning and attention to timing, you can easily enjoy a bountiful harvest within our roughly 108-day growing season.

Starting Calendula indoors is an option, especially if you want a head start on the season. Sow seeds indoors from late March through mid April, about six weeks before you intend to transplant them outside. Use seed trays with a good seed-starting mix, and keep them in a warm location with plenty of light.

A heat mat can help speed up germination. Bottom watering is a great way to keep the soil consistently moist without overwatering, which can be especially important during our variable Plains springs.

Transplant your Calendula seedlings outdoors from mid May through late June, after the risk of frost has passed. Before transplanting, be sure to harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature swings that are common in our region.

Space the plants 8-12 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast – a late frost or unexpected hail can still happen, so be prepared to cover your young plants if needed.

Direct sowing Calendula is a simple and effective method, especially if you're looking for a low-maintenance approach. Sow seeds directly into the garden from mid May through mid July, after the soil has warmed up. Choose a sunny location with well-drained soil.

Prepare the soil by loosening it and removing any weeds or debris. Sow seeds about ½ inch deep and space them 8-12 inches apart. Keep the soil consistently moist until the seedlings emerge. Direct sowing is a good bet if you're worried about disturbing roots during transplant, but you'll need to be vigilant about weeding.

Calendula needs moderate watering, but it's not very drought-tolerant, so you'll need to pay attention, especially during our hot, dry summers. The key is to find a balance, as overwatering can lead to problems like root rot.

During the spring, when temperatures are cooler and rainfall is more frequent, water your Calendula about once a week, providing about an inch of water. As the summer heat intensifies, you may need to increase watering to two or three times a week, especially if you are getting less than 15 inches of rain. Use the finger test: stick your finger about two inches into the soil near the base of the plant. If the soil feels dry, it's time to water.

Water at the base of the plants rather than overhead to minimize the risk of fungal diseases, especially with our low-to-moderate humidity. Signs of underwatering include wilting leaves and stunted growth. Overwatering can cause yellowing leaves and root rot. A layer of mulch around the base of the plants can help retain moisture and suppress weeds, which is especially helpful in our often windy conditions.

Regular pruning, specifically deadheading, is essential for keeping your Calendula plants blooming throughout the season. Deadheading means removing spent or faded flowers. This encourages the plant to produce more blooms rather than putting energy into seed production.

Simply pinch or cut off the flower heads just below the base of the flower, leaving the stem intact. Do this every few days or once a week, depending on how quickly the flowers fade. As the first frost approaches in early September, you can let some of the flowers mature and develop seeds if you want to save them for next year or allow the plants to self-seed.

You can expect your first Calendula harvest from late June through mid September, about 45 days after planting. Harvest the flowers when they are fully open, ideally in the morning after the dew has dried. The petals are most flavorful and potent when the flowers are at their peak.

To harvest, simply snip off the flower heads with scissors or garden shears. Be careful not to damage the surrounding foliage. Regular harvesting encourages the plant to produce more flowers, so keep harvesting throughout the season.

As the first frost approaches, harvest any remaining flowers before they are damaged by the cold. You can dry the petals for later use.

Here are some common problems you might encounter with Calendula in the Great Plains:

Powdery Mildew

• What it looks like: A white or grayish powdery coating on the leaves, stems, and sometimes the flower buds. The leaves may curl, yellow, and eventually die.
• What causes it: Powdery mildew is caused by various fungi that thrive in warm days, cool nights, and moderate humidity. It's more common in crowded plantings with poor air circulation. Surprisingly, dry leaf surfaces favor it here.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning if needed. Remove and dispose of affected leaves. You can try neem oil or potassium bicarbonate sprays. A milk spray (1 part milk to 9 parts water) can also be effective.

Aphids

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

Whiteflies

• What it looks like: Tiny, white, moth-like insects that flutter around the plant when disturbed. Yellowing leaves, stunted growth, and sticky honeydew.
• What causes it: Whiteflies are sap-sucking insects that thrive in warm, dry conditions. They can quickly build up large populations.
• How to fix/prevent it: Yellow sticky traps can help catch adult whiteflies. Strong sprays of water can dislodge them. Insecticidal soap or neem oil can be effective, but multiple applications may be needed. Encourage beneficial insects like lacewings and ladybugs.

Great Plains Specific Challenges: Calendula generally handles our hot, dry conditions pretty well, but the extreme temperature swings can stress the plants, making them more susceptible to problems. The wind can also spread fungal diseases and insect pests quickly. Consistent monitoring and prompt action are key to keeping your Calendula healthy in our challenging climate.

Calendula makes a great companion plant for several vegetables in the Great Plains garden. Planting Calendula near tomatoes and peppers can help repel pests like tomato hornworms and aphids, protecting your precious crops. The strong scent of Calendula also deters bean beetles, making it a good companion for green beans.

Avoid planting Calendula near members of the cabbage family, as they can attract cabbage moths. Overall, Calendula is a welcome addition to most vegetable gardens, bringing beauty, attracting pollinators, and helping to protect your other plants.