Calendula in Zone 6A — Midwest

Calendula is a cheerful and useful addition to any Midwest garden. The bright, sunny flowers bring a pop of color, and the petals can be used in salads or infused in oils for their medicinal properties. Plus, attracting pollinators to your garden always pays off!

Midwest weather can be unpredictable, with variable springs and summer heat spells. But don't worry, Calendula is fairly easy to manage if you time things right. With our 178-day growing season, you'll have plenty of time to enjoy its blooms.

Starting Calendula indoors is an option, but honestly, it's not usually necessary here in the Midwest. Our fertile soil and decent growing season mean direct sowing often works just fine. But if you're eager to get a head start, go for it!

You can start seeds indoors from mid February through early March, about 6 weeks before you plan to transplant. Use seed trays with a good seed-starting mix and keep them warm and well-lit. Bottom watering helps prevent damping-off, which can be a problem during our moderate-to-late springs.

Once the danger of hard frost has passed – usually early April through mid May here in the Midwest – you can transplant your Calendula seedlings outdoors. Be sure to harden them off first by gradually exposing them to outdoor conditions for about a week. This prevents transplant shock.

Plant them 8-12 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast, though. We sometimes get unexpected cold snaps in early spring, so be ready to cover your seedlings if needed.

Direct sowing Calendula is a breeze in the Midwest. You can sow seeds directly into the garden from early April through mid August. The fertile soil warms up nicely by then.

Just make sure the soil is loose and weed-free. Plant the seeds about 1/4 inch deep and keep the soil consistently moist until they germinate. Thin the seedlings to 8-12 inches apart once they're a few inches tall. The advantage of direct sowing is avoiding transplant shock.

Calendula needs moderate watering, but it's pretty forgiving. In the Midwest, with our wet summers, you usually don't have to water constantly. However, consistent watering is especially important during the establishment period.

During the spring and fall, when temperatures are cooler, water thoroughly once or twice a week, providing about an inch of water each time. The finger test is a good guide: stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. During summer heat spells, you might need to water more frequently. Aim to water at the base of the plant to avoid creating humid conditions around the foliage, which can encourage fungal diseases.

Overwatering can lead to root rot, so watch for yellowing leaves and a generally unhappy plant. Underwatering will cause wilting. A layer of mulch, like shredded leaves or straw, helps retain moisture and regulate soil temperature, especially helpful during our summer heat spells.

Deadheading is key to keeping your Calendula blooming throughout the season. Simply pinch or snip off the spent flowers just below the flower head. This encourages the plant to produce more blooms instead of setting seed.

Do this regularly, every few days or once a week, depending on how quickly your plants are flowering. Towards the end of the season, around the time of our first frost in mid- October, you can let some of the flowers mature and set seed if you want them to self-sow or if you want to collect seeds for next year.

You can expect your first Calendula harvest about 45 days after planting, so from late May through late October here in the Midwest. Harvest the flowers when they are fully open and the petals are at their brightest.

Gently pluck the entire flower head from the stem. You can use scissors or just pinch them off with your fingers. Harvesting regularly encourages the plant to produce more flowers. As the first frost approaches, harvest any remaining flowers to dry and use later, since the cold will quickly put an end to production.

Even in the Midwest's fertile conditions, Calendula can face a few common problems:

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems. Leaves might curl, yellow, and die.
• What causes it: Fungi that thrive in warm days, cool nights, and moderate humidity – pretty typical Midwest conditions. Dry leaf surfaces actually make it worse.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help. Surprisingly, a milk spray (1 part milk to 9 parts water) can be effective.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Sap-sucking insects that reproduce rapidly, especially in warm weather. Ant colonies may farm them.
• How to fix/prevent it: Knock them off with a strong water spray. Encourage ladybugs and lacewings (natural predators). Use insecticidal soap for heavy infestations. Neem oil works systemically. Avoid excess nitrogen fertilizer.

Whiteflies

• What it looks like: Tiny white, moth-like insects that flutter up when disturbed. Yellowing or silvering of leaves. Sticky honeydew residue.
• What causes it: Warm weather and high humidity. They suck plant sap, weakening the plant.
• How to fix/prevent it: Use yellow sticky traps to catch adults. Spray with insecticidal soap or neem oil, focusing on the undersides of leaves. Encourage natural predators like lacewings and parasitic wasps.

Midwest Specific Challenges: Our moderate-to-hot summers and moderate-to-humid humidity can make Calendula more susceptible to powdery mildew and whiteflies. Make sure to provide good air circulation and monitor your plants regularly. The wet-summer rainfall also makes it more important to water at the base of the plant to avoid fungal issues.

Calendula makes a great companion plant in the Midwest garden. Plant it near tomatoes and peppers. Calendula attracts beneficial insects like ladybugs and hoverflies, which prey on aphids and other pests that can bother your tomatoes and peppers.

It's also a good companion for green beans. Calendula can attract pollinators, improving bean yields. Avoid planting Calendula near plants in the cabbage family, as it can attract cabbage white butterflies that lay eggs on those plants.