Calendula in Zone 6A — Great Plains

Calendula is a fantastic flower to grow in the Great Plains. Its cheerful blooms add color to your garden, the petals are edible (try them in salads!), and they attract beneficial insects. Plus, they're pretty low-maintenance, which is always a win with our unpredictable weather.

Our region's extreme temperature swings and occasional hail can be tough on plants. But Calendula's relatively quick maturity makes it a great fit for our roughly 188-day growing season. With the right timing, you'll get plenty of blooms.

Starting Calendula indoors gives you a jump start, but it's not always necessary. If you're itching to get your hands dirty early, or if you want blooms as early as possible, then starting indoors is a good choice.

Sow seeds mid-February through early March, about six weeks before you plan to transplant. Use seed trays with a good seed-starting mix, keep them warm (a heat mat helps), and provide plenty of light (grow lights are best). Don't forget to water from the bottom to avoid damping off, which can be a problem with our variable spring weather.

Transplant your Calendula seedlings outdoors early April through mid May, once the danger of hard frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature fluctuations we often get in spring.

Space your plants 8-12 inches apart to allow for good air circulation. Be prepared to protect them from late-season frosts or unexpected hail storms – row covers or even buckets can do the trick in a pinch.

Direct sowing Calendula is easy and often just as successful as starting indoors. The main advantage is less work! The downside is you have to wait for the soil to warm up.

Sow seeds early April through late August, after the soil temperature reaches at least 60°F. Prepare the soil by loosening it and removing any weeds. Sow seeds about ½ inch deep and space them 8-12 inches apart. Keep the soil consistently moist until the seedlings emerge.

Calendula needs moderate watering, but it's not very drought-tolerant, so don't let it dry out completely, especially when it's young. Our variable rainfall means you'll need to pay close attention to the soil moisture. The hotter it gets, the more you'll need to water.

During the cooler spring and fall, water deeply about once a week, providing about an inch of water. In the heat of summer, you might need to water every other day, or even daily if it's exceptionally hot and dry. Stick your finger about two inches deep into the soil – if it feels dry, it's time to water.

Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our low-to-moderate humidity. A layer of mulch around the plants helps retain moisture and suppress weeds, which is especially helpful during our hot, dry spells. Watch for signs of underwatering (wilting, yellowing leaves) or overwatering (yellowing leaves, mushy stems).

Deadheading is key to keeping your Calendula plants blooming throughout the season. Simply pinch or cut off the spent flowers just below the flower head. This encourages the plant to produce more blooms instead of putting energy into seed production.

Deadhead regularly throughout the growing season, from mid May through late October. As the first frost approaches in mid- October, you can let some of the last flowers mature and go to seed if you want them to self-sow for next year.

You can expect your first Calendula harvest about 45 days after planting, usually starting in mid May and continuing through late October. Harvest the flowers when they are fully open, ideally in the morning after the dew has dried.

To harvest, simply snip the flower heads off the stem just below the bloom. Be gentle to avoid damaging the plant. Regular harvesting encourages more flower production, so the more you harvest, the more you'll get.

As the first frost approaches, harvest any remaining open flowers. You can dry them for later use or use them fresh. If you want to save seeds for next year, let some of the flower heads dry completely on the plant.

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

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems. Leaves curl, yellow, and die.
• What causes it: Fungi thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it. Our temperature swings can create ideal conditions.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning. Remove affected leaves. Neem oil or potassium bicarbonate sprays help. Milk spray (1 part milk to 9 parts water) is surprisingly effective.

Aphids

• What it looks like: Clusters of tiny insects (green, black, or white) on stems and leaf undersides. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Rapid-reproducing sap-sucking insects. Populations explode in warm weather. Our warm summers can lead to rapid infestations.
• How to fix/prevent it: Strong water spray knocks them off. Encourage ladybugs and lacewings. Insecticidal soap for heavy infestations. Neem oil works systemically.

Whiteflies

• What it looks like: Tiny white, moth-like insects that fly up when disturbed. Yellowing or silvering leaves. Sticky honeydew residue. Sooty mold growth.
• What causes it: 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 capture adults. Strong water sprays dislodge them. Insecticidal soap or neem oil can control infestations. Encourage beneficial insects like lacewings and parasitic wasps.

Great Plains Specific Challenges: The hot, dry summers in the Great Plains can stress Calendula, making it more susceptible to pests and diseases. Our variable rainfall can also make it difficult to maintain consistent soil moisture. Wind protection is essential to prevent damage to the plants, especially young seedlings.

Calendula makes a great companion plant for several vegetables in the Great Plains garden. Plant it near tomatoes and peppers to attract beneficial insects like ladybugs and lacewings, which will help control aphids and other pests. It also does well near green beans, attracting pollinators and acting as a trap crop for bean beetles.

Avoid planting Calendula near plants that are susceptible to powdery mildew, as it can sometimes spread the disease. There aren't any specific bad companions to call out, but use common sense and give everything enough space.