Calendula in Zone 6B — Mountain West

Calendula is a fantastic addition to any Mountain West garden. It's incredibly versatile – the petals add a pop of color and a slightly peppery flavor to salads, and they also have medicinal properties. Plus, the bright orange and yellow blooms are just cheerful, and they attract pollinators to your garden, something we always need at our high altitude.

Our short season and intense sun here in Zone 6B can be challenging, but Calendula is pretty forgiving. With a 163-day growing season, you have plenty of time to get a good harvest if you time things right.

Starting Calendula indoors gives you a jump start on our relatively short growing season, but it's not always necessary. If you're aiming for the earliest possible blooms, or want to ensure you get a harvest before the first frosts, starting indoors is a good idea.

Start your seeds indoors late February through mid March, about six weeks before you plan to transplant them. Use seed trays with a good seed-starting mix, and keep them warm (around 70°F) until germination. Bottom watering helps prevent damping off, which can be a problem in cooler indoor environments. A simple grow light will help prevent leggy seedlings, especially with our intense spring sun.

Transplant your Calendula seedlings outdoors mid April through late May, after the danger of hard frost has passed. Be sure to harden them off for about a week before transplanting. Gradually expose them to outdoor conditions, starting with just a few hours a day, to acclimate them to the intense sun and cooler temperatures.

Plant them 8-12 inches apart in well-draining soil. Even though our last frost is *around* late April, be prepared to cover your transplants if we get a late cold snap.

Direct sowing Calendula is easy and often successful in our region. The plants are fairly adaptable, and direct sowing saves you the trouble of starting seeds indoors.

Sow seeds mid April through early August, after the soil has warmed up a bit. Calendula germinates best when the soil temperature is around 65-70°F. Prepare the soil by loosening it and removing any rocks or debris. Sow seeds about 1/4 inch deep and 8-12 inches apart. Keep the soil consistently moist until the seedlings emerge. Direct sowing later in the season will give you blooms later into the fall.

Watering Calendula in our dry Mountain West climate requires a bit of attention, but it's not too demanding. While they can tolerate some drought, consistent moisture is key for optimal growth and blooming. Remember, even though it's Zone 6B, our high altitude and dry air make watering a critical skill.

In the spring, when temperatures are cooler, water deeply but less frequently – maybe once or twice a week, depending on rainfall. Use the finger test: stick your finger about 2 inches into the soil, and if it feels dry, it's time to water. Aim for about 1 inch of water per week. As the weather warms up in the summer, you'll likely need to water more often, especially during dry spells.

Water at the base of the plants to avoid wetting the foliage, which can encourage powdery mildew even in our low humidity. Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to root rot, so make sure the soil is well-draining. Yellowing leaves can indicate either problem. A light layer of mulch, like shredded bark or straw, will help retain moisture and keep the soil cool.

Deadheading is essential for keeping your Calendula plants blooming throughout the season. 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 regularly, every few days or once a week, from late spring through fall. Towards the end of the season, around the time of our first frost in early October, you can let some of the flowers mature and form seeds if you want to collect them for next year or allow them to self-seed.

You can expect your first Calendula harvest late May through mid October, about 45 days after planting. The flowers are ready to harvest when they are fully open.

To harvest, simply snip off the flower heads with scissors or your fingers. Harvest in the morning after the dew has dried for the best flavor and medicinal properties. Regular harvesting encourages continuous blooming. As the first frost approaches, harvest all the remaining flowers, even if they aren't fully open. You can dry them indoors for later use.

Calendula is generally easy to grow, but here are a few common problems you might encounter in the Mountain West:

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems. Leaves curl, yellow, and die.
• What causes it: Fungi that thrive in warm days, cool nights, and moderate humidity (or even dry leaf surfaces). Our temperature swings at altitude can make this tricky.
• How to fix/prevent it: Improve air circulation by spacing plants properly. 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: 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, moth-like insects that fly up when disturbed. Yellowing or stippled leaves. Sticky honeydew.
• What causes it: Sap-sucking insects that thrive in warm, dry conditions. Overcrowding and poor air circulation contribute.
• How to fix/prevent it: Yellow sticky traps attract and capture them. Strong water spray dislodges them. Insecticidal soap or neem oil. Ensure good air circulation.

Mountain West Specific Challenges: Our intense sun can sometimes scorch Calendula leaves, so providing some afternoon shade can be beneficial, especially for plants in hotter locations. The dry air can also exacerbate pest problems, so regular monitoring is key. And, of course, be prepared for hail, which can damage the plants.

Calendula makes a great companion plant in the Mountain West garden. Plant it near tomatoes and peppers to attract pollinators and deter pests like aphids. The strong scent of Calendula can help mask the scent of these crops, making them less attractive to pests.

Calendula is also a good companion for green beans. It attracts beneficial insects that prey on bean pests. I would avoid planting it near anything that is particularly susceptible to powdery mildew, as Calendula can sometimes be affected, and you don't want to spread the problem.