Calendula in Zone 6A — Mountain West

Calendula is a fantastic addition to any high-altitude garden. Its bright, cheerful flowers are not only beautiful, but also edible and medicinal, adding a splash of color and practicality to your Mountain West landscape. Plus, the cool nights we get here actually intensify the flavors and benefits!

Our short growing season and intense sun can be a challenge, but Calendula's relatively quick maturity (around 45 days) means you can easily fit in a crop or two. With a little planning around our 153-day season, you'll be enjoying blooms from early summer well into fall.

Starting Calendula indoors is an option, especially if you want a head start on our short growing season. Starting seeds indoors from late February through mid March gives you about a 6-week jump on the season. This is especially helpful if you're aiming for an early harvest.

Use seed trays with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light – a grow light works wonders, as our spring can be a bit unpredictable and late. Bottom watering is a great way to keep the soil consistently moist without overwatering.

Transplant your Calendula seedlings outdoors from mid April through late May, after the danger of hard frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense sun and cooler nights that are typical in the Mountain West.

Space the plants 8-12 inches apart to allow for good air circulation. Keep an eye on the weather forecast – a late cold snap or even hail is always possible, so be ready to cover your young plants if necessary.

Direct sowing Calendula is a simple and effective method, and it works well in our climate. Sow seeds from mid April through early August, ensuring you have time for them to mature before our first frost. Direct sowing is easier but you will give up some growing time.

Prepare the soil by loosening it and removing any rocks or debris. Calendula isn't too fussy, but a little compost mixed in will help. Sow seeds about ½ inch deep and keep the soil consistently moist until they germinate. Thin seedlings to 8-12 inches apart once they emerge.

Calendula needs moderate watering, but it's important to get it right in our dry Mountain West climate. While it can tolerate some drought, consistent moisture will keep it blooming its best. You'll want to adjust your watering based on the season and rainfall.

During the cooler spring and fall months, water deeply about once a week, providing around 1 inch of water. Use the finger test – if the top 2 inches of soil are dry, it's time to water. In the heat of summer (which is moderate at altitude), you might need to water every 2-3 days, especially if we're not getting any rain.

Water at the base of the plants to avoid wetting the foliage, as this can encourage powdery mildew. Overhead watering is fine if done early in the day so the foliage can dry quickly. Signs of underwatering include wilting leaves and stunted growth, while overwatering can lead to yellowing leaves and root rot. A layer of mulch around the plants helps retain moisture and keeps the soil cool.

Regular deadheading is key to 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 rather than putting energy into seed production.

Continue deadheading throughout the summer and into the fall. If you want to collect seeds, allow a few flowers to mature and dry on the plant. As our first frost approaches in early October, you can either let the plants self-seed or collect the seeds to sow next spring.

You can expect your first Calendula harvest about 45 days after planting, typically from early June through early October in our region. Harvest the flowers when they are fully open and the petals are bright and vibrant. The petals are most potent in the morning after the dew has dried.

To harvest, simply snip the flower heads off the plant with scissors or pruning shears. Be careful not to damage the surrounding foliage. Harvesting regularly encourages the plant to produce more blooms, so keep at it throughout the season.

As the first frost approaches, harvest any remaining flowers, even if they aren't fully open. You can dry them indoors for later use. Calendula is a continuous harvest plant; the more you harvest, the more it produces.

Here are some common problems you might encounter with Calendula in the Mountain West:

Powdery Mildew

• What it looks like: A white or grayish powdery coating on leaves and stems. Leaves may curl, yellow, and die.
• What causes it: Fungi that thrive in warm days, cool nights, and moderate humidity. Interestingly, dry leaf surfaces can actually favor it in our climate.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help. A milk spray (1 part milk to 9 parts water) is also effective.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. Sticky honeydew residue and curled or distorted new growth are also signs.
• What causes it: Rapidly reproducing sap-sucking insects. Populations can explode in warm weather.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage natural predators like ladybugs. Insecticidal soap is effective for heavy infestations. Avoid over-fertilizing with nitrogen, as this attracts them.

Whiteflies

• What it looks like: Tiny white, moth-like insects that fly up when disturbed. Yellowing leaves and sticky honeydew are also signs.
• What causes it: Sap-sucking insects that thrive in warm conditions. They can quickly infest plants.
• How to fix/prevent it: Sticky traps can help catch adult whiteflies. Insecticidal soap or neem oil can control infestations. Ensure good air circulation and avoid overcrowding.

Mountain West Specific Challenges: Our intense sun can sometimes scorch Calendula leaves, so providing some afternoon shade can be helpful. Our alkaline soil can also be a factor, so amend your soil with compost to improve its pH and nutrient content. Hail can also damage the plant, so consider protecting it with netting during severe storms.

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

It's also a good companion for green beans, as it helps to attract pollinators, leading to better bean production. There aren't any specific plants to avoid planting near Calendula, but be mindful of providing enough space and sunlight for all your plants to thrive.