Calendula in Zone 5B — Great Plains

Calendula is a fantastic addition to any Great Plains garden. Its cheerful blooms bring bright color, and the petals add a subtle peppery note to salads. Plus, they’re incredibly useful for homemade salves and tinctures to soothe dry skin, a common issue with our low-humidity climate.

Our region’s extreme weather can be unpredictable, but Calendula's relatively short 45-day maturity makes it a winner even with our 178-day growing season. With proper timing and a little protection from the elements, you can enjoy a long harvest of these sunny flowers.

Starting Calendula indoors is an option, but not strictly necessary. If you want a head start, especially in the northern Plains where the growing season is shorter, sow seeds mid-February through early March, about six weeks before you plan to transplant.

Use seed trays with a good seed-starting mix and keep them in a warm spot with plenty of light – a sunny south-facing window or under grow lights works well. Water from the bottom to avoid damping off. Keep in mind that our variable spring weather can make timing tricky, so be prepared to adjust based on the forecast.

Transplant your Calendula seedlings outdoors early April through mid May, after the danger of hard frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature swings common in the Plains.

Plant them 8-12 inches apart in well-draining soil. Keep an eye on the forecast; a late frost can still happen, so be ready to cover them if needed.

Direct sowing Calendula is easy and often just as successful as starting indoors. Sow seeds early April through mid August, once the soil has warmed up a bit. Aim for a soil temperature of at least 60°F.

Prepare the soil by loosening it and removing any weeds. Sow seeds about ½ inch deep and 8-12 inches apart. Keep the soil consistently moist until the seedlings emerge. Direct sowing is less work, but seedlings will be more vulnerable to pests and weather fluctuations.

Calendula prefers moderate watering, but it's crucial to adjust your schedule based on our unique Plains climate. During the spring, when rainfall is more frequent, you may only need to water once a week, if at all.

As the summer heat kicks in, increase watering to 1-2 times per week, providing about an inch of water each time. Use the finger test: stick your finger about two inches 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 sometimes humid conditions.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to yellowing leaves and root rot. A layer of mulch, like straw or wood chips, helps retain moisture and regulate soil temperature, which is especially helpful during our hot summers.

Deadheading is key to keeping your Calendula plants blooming throughout the season. Regularly remove spent flowers by snipping them off just below the flower head. This encourages the plant to produce more blooms instead of setting seed.

Continue deadheading throughout the summer and into the fall. As the first frost approaches around mid- October, you can let some of the last flowers mature and set seed if you want them to self-sow next year. Otherwise, remove all the spent flowers to prevent unwanted seedlings.

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

Gently pinch or snip the flower heads off the plant, leaving the stem intact. Harvesting regularly encourages continued blooming. The petals are most potent when the flowers are fully open and vibrant.

As the end of the season approaches and frost threatens, harvest any remaining open flowers. You can dry them for later use or infuse them in oil for medicinal purposes.

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 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 it.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning if needed. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help. A milk spray (1 part milk to 9 parts water) is surprisingly effective.

Aphids

• What it looks like: Clusters of tiny soft-bodied 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. Ant colonies may farm them for honeydew.
• How to fix/prevent it: A strong water spray can knock them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap is effective 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 of leaves. Sticky honeydew residue.
• What causes it: Sap-sucking insects that thrive in warm, dry conditions. They weaken plants by feeding on their sap.
• How to fix/prevent it: Hang yellow sticky traps to catch adults. Vacuum them off plants in the early morning when they are less active. Insecticidal soap or neem oil can help control infestations.

Great Plains Specific Challenges: Our hot summers can stress Calendula, making them more susceptible to pests and diseases. The wind can also damage plants, so providing some wind protection is essential. Variable rainfall means you need to be vigilant about watering, especially during dry spells.

Calendula makes a great companion plant in the Great Plains garden. Plant them near tomatoes and peppers to attract beneficial insects that prey on common pests like aphids. They also do well near green beans, as they help deter bean beetles. Avoid planting Calendula near plants in the brassica family (cabbage, broccoli, kale), as they can sometimes attract cabbage moths.