Calendula in Zone 6B — Midwest

Calendula is a fantastic addition to any Midwest garden. Its bright, cheerful flowers offer a splash of color, attracting pollinators to your tomatoes and peppers. Plus, the petals are edible, adding a peppery zest to salads, and they're known for their medicinal properties, making salves and teas.

Our Midwest weather can be unpredictable, but Calendula is surprisingly resilient. With our 183-day growing season, you'll have plenty of time to enjoy its blooms, even with our variable spring and occasional summer heat spells. Getting the timing right makes all the difference.

Starting Calendula indoors isn't essential, but it can give you a head start, especially if you're eager for those first blooms. If you want to get a jump on the season, aim to sow your seeds indoors from mid February through early March, roughly six weeks before you plan to transplant them outside.

Use seed trays with a good seed-starting mix. Keep them warm – a heat mat helps – and provide plenty of light, either from a sunny window or a grow light. Bottom watering is great to keep the seedlings evenly moist without damping off. Since our spring weather in the Midwest can be moderate-to-late, this indoor start ensures you're not waiting too long for flowers.

Once the danger of hard frost has passed – usually sometime between early April and mid May here in the Midwest – you can transplant your Calendula seedlings outdoors. Before planting them in the ground, harden them off by gradually exposing them to outdoor conditions for about a week.

Plant them 8-12 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast though. We can still get some cool snaps even in early April, so be prepared to cover your seedlings if a late frost threatens.

Direct sowing Calendula is a simple and effective method, and honestly, it's my preferred way to grow them. You can sow seeds directly into the garden from early April through mid August. This long window means you can succession sow for continuous blooms.

Make sure the soil is loose and workable. Calendula seeds germinate best when the soil temperature is around 70°F (21°C). Sow seeds about ¼ inch deep and keep the soil consistently moist. Thin seedlings to 8-12 inches apart once they emerge. The only downside? You'll be waiting a bit longer for those first flowers compared to starting indoors.

Calendula prefers moderate watering, and while it can tolerate some drought, it definitely thrives with consistent moisture, especially during our Midwest summer heat spells. However, our moderate-to-humid conditions mean you need to be careful not to overwater.

During the spring and fall, when temperatures are cooler and rainfall is more frequent, you might only need to water once or twice a week, depending on how much rain we get. Use the finger test: stick your finger about two inches into the soil. If it feels dry, it's time to water. Aim for about an inch of water per week.

In the heat of summer, you might need to water more frequently, especially if we're experiencing a dry spell. Water at the base of the plants to avoid wetting the foliage, which can increase the risk of fungal diseases in our humid climate. Yellowing leaves can be a sign of overwatering, while wilting leaves indicate underwatering. A layer of mulch around your Calendula plants will help retain moisture and keep the soil cool.

Regular deadheading is key to keeping your Calendula plants blooming all season long. Simply pinch or cut off the spent flower heads just below the bloom. This encourages the plant to produce more flowers instead of putting energy into seed production.

Deadhead throughout the growing season, from mid May through late October. If you want Calendula to self-seed, leave a few flowers on the plant towards the end of the season to mature and drop their seeds. Before our first frost arrives around mid- October, you can let the last blooms fade to encourage self-seeding for the following year.

You can expect your first Calendula harvest about 45 days after planting, usually sometime between mid May and late October in our region. The best time to harvest the flowers is when they are fully open, ideally in the morning after the dew has dried.

Gently snip the flower heads from the plant, leaving about an inch of stem attached. To encourage continued production, harvest regularly. If you're mainly interested in the petals, you can pluck them off the flower heads after harvesting.

As the first frost approaches in mid- October, harvest all remaining flowers, even the ones that aren't fully open. You can dry them indoors for later use. If you've let some flowers go to seed, collect the dried flower heads and store them in a cool, dry place for planting next year.

Even though Calendula is relatively easy to grow, it can still encounter some problems in our Midwest gardens. Here are three common issues to watch out for:

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems. Leaves curl, yellow, and die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces favor it. Our moderate-to-humid summers can create ideal conditions.
• How to fix/prevent it: Improve air circulation through spacing 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 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. Our warm summers can lead to rapid infestations.
• How to fix/prevent it: Strong water spray knocks them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap for heavy infestations. Neem oil works systemically. Avoid excess nitrogen fertilizer (it attracts them).

Whiteflies

• What it looks like: Tiny white insects that fly up when disturbed. Yellowing leaves. Sticky honeydew residue.
• What causes it: Sap-sucking insects that thrive in warm, humid conditions. Our Midwest summers can be perfect for them.
• How to fix/prevent it: Yellow sticky traps can catch adult whiteflies. Strong water spray can knock them off plants. Insecticidal soap or neem oil are effective treatments.

Midwest Specific Challenges: Calendula prefers cooler weather, so our moderate-to-hot summer heat spells can cause it to slow down or even go dormant. Make sure to provide adequate water during these periods and consider providing some afternoon shade. Our wet-summer rainfall can also increase the risk of fungal diseases like powdery mildew, so good air circulation is essential.

Calendula makes a great companion plant in the Midwest garden. It attracts beneficial insects that can help protect your other plants.

Good companions:

• Tomato: Calendula attracts pollinators, which can improve tomato yields. Plus, it helps repel tomato hornworms.
• Pepper: Like tomatoes, peppers benefit from the increased pollination provided by Calendula.
• Beans-green: Calendula can help repel bean beetles, protecting your bean crop.

Bad companions: Calendula doesn't really have any specific bad companions that are widely known.