Calendula in Zone 7A — Midwest

Calendula is a fantastic addition to any Midwest garden. Its cheerful blooms bring color to your beds, plus the petals are edible and can be used in homemade salves. The plant thrives in our fertile soil and provides a long harvest window, from late spring right through fall, which is a treat for us here in Zone 7A.

Our Midwest weather can be unpredictable, with occasional late frosts in spring and summer heat spells. But with careful timing and a little attention, Calendula is easy to manage. Our long 193-day growing season gives you plenty of time to enjoy these sunny flowers.

Starting Calendula indoors isn't essential, as it direct sows readily, but it can give you a head start, especially if you're itching to garden before our unpredictable springs fully settle. Starting seeds indoors from early to late February allows you to get blooms earlier.

Use seed trays or small pots with a good seed-starting mix. Keep them warm and provide plenty of light – a simple grow light works wonders. Don't forget to water from the bottom to prevent damping off. Our springs here in the Midwest can be moderate-to-late, so getting a jump start indoors is a great option!

Transplanting Calendula seedlings outdoors can be done from late March through early May, once the risk of hard frost has passed. Be sure to harden off your seedlings for about a week before transplanting. Gradually expose them to outdoor conditions for a few hours each day to toughen them up.

Plant them 8-12 inches apart in well-drained soil. Keep an eye on the weather forecast, as we can still get unexpected cold snaps here in the Midwest. A row cover can protect your young plants if needed.

Direct sowing Calendula is a simple and effective method in the Midwest. You can sow seeds directly into the garden from late March through late August. This allows for a continuous supply of blooms throughout the growing season.

Prepare the soil by loosening it and removing any weeds. Sow the seeds about ½ inch deep and 8-12 inches apart. Keep the soil consistently moist until the seedlings emerge. Direct sowing is a great option for our fertile soil, and you don’t have to worry about disturbing the roots.

Calendula needs moderate watering, especially during our Midwest summers. While it can tolerate short periods of drought, consistent moisture is key for healthy growth and abundant blooms.

During the spring and fall, when temperatures are cooler and rainfall is more frequent, water deeply about once a week, providing about an inch of water. During our hotter summer months, increase watering to two or three times a week, depending on rainfall. Stick your finger about 2 inches deep into the soil – if it feels dry, it’s time to water.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our moderate-to-humid environment. Overwatering can lead to root rot, so watch for yellowing leaves. Underwatering will cause the plant to wilt and the leaves to turn brown. A layer of mulch helps retain moisture and keeps the soil cool, which Calendula loves.

Deadheading is essential for keeping your Calendula plants blooming throughout the season. Regularly remove spent flowers to encourage the plant to produce more buds. Simply pinch or cut off the flower heads just below the base of the flower.

Leave some flowers to mature if you want the plant to self-seed. Calendula will readily drop its seeds, giving you a free crop of plants the following year. As our first frost approaches around mid- October, you can let the remaining flowers go to seed or harvest them for their petals.

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

Gently pinch or cut the flower heads from the stem, being careful not to damage the plant. Continued harvesting encourages more blooms, so keep at it! As the end of the season approaches and the first frost looms, harvest all remaining open flowers.

Here are some common problems you might encounter with Calendula in your Midwest garden:

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes flower buds. The leaves may curl, yellow, and eventually die, reducing the plant's overall vigor.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity – conditions we often see in the Midwest. Surprisingly, dry leaf surfaces actually favor powdery mildew.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning overcrowded growth. Remove and discard affected leaves immediately. Treat with neem oil or potassium bicarbonate sprays. A milk spray (1 part milk to 9 parts water) can also be surprisingly effective.

Aphids

• What it looks like: Clusters of tiny, soft-bodied insects (green, black, or white) on stems and leaf undersides. You might also notice a sticky honeydew residue and curled or distorted new growth.
• What causes it: Rapidly reproducing sap-sucking insects. Populations tend to explode during warm weather, which we certainly get during our Midwest summers. Ant colonies may even "farm" them for their honeydew.
• How to fix/prevent it: A strong spray of water from your hose can knock them off plants. Encourage natural predators like ladybugs and lacewings. For heavy infestations, use insecticidal soap or neem oil. Avoid excessive nitrogen fertilizer, as it attracts aphids.

Whiteflies

• What it looks like: Tiny white, moth-like insects that fly up in a cloud when disturbed. Yellowing or silvering leaves. Sticky honeydew residue.
• What causes it: Sap-sucking insects that thrive in warm, humid conditions. Overcrowding and poor air circulation make the problem worse.
• How to fix/prevent it: Use yellow sticky traps to catch adult whiteflies. Spray plants with insecticidal soap or neem oil, paying close attention to the undersides of leaves. Ensure good air circulation.

Midwest Specific Challenges: The moderate-to-hot heat and moderate-to-humid humidity of our Midwest summers can create conditions that favor fungal diseases and pests. Good air circulation, proper watering techniques, and regular monitoring of your plants will help keep your Calendula healthy and thriving.

Calendula makes a great companion plant in the Midwest garden! Plant it near tomatoes and peppers to help deter pests like tomato hornworms and aphids. Calendula attracts beneficial insects like ladybugs and hoverflies, which prey on these pests.

Green beans also benefit from being planted near Calendula. The flowers attract pollinators, which can increase bean production. Avoid planting Calendula near plants that are susceptible to powdery mildew, as it can spread the disease.