Calendula in Zone 3A — Mountain West

Calendula is a fantastic addition to any high-altitude garden. Its bright, cheerful flowers bring pops of color to our short season, and the petals add a peppery zing to salads. Plus, it's incredibly satisfying to grow your own medicinal herbs in our challenging climate.

Our Zone 3A growing season is short, about 96 days, and we all know about the temperature swings we can get even in summer. But with careful timing and a few tricks, you can easily enjoy a beautiful and bountiful Calendula harvest right here in the Mountain West.

Starting Calendula indoors is an option, especially if you're aiming for the earliest possible blooms. Begin in late March through mid April, about six weeks before you plan to transplant. It gives you a head start against our late spring.

Use seed trays or small pots filled with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light – a sunny windowsill or grow light works well. Remember to water from the bottom to avoid damping off.

Transplant your Calendula seedlings outdoors mid May through late June, once the risk of hard frost has passed. Before planting, harden them off for about a week by gradually exposing them to outdoor conditions. This helps them adjust to our intense sun and cooler nights.

Space your plants 8-12 inches apart to allow for good air circulation. Keep an eye on the weather forecast – a late frost or hailstorm can still happen, so be ready to cover your seedlings if needed.

Direct sowing Calendula is easy and often just as successful as starting indoors, especially if you don't need a super early start. Wait until mid May through early July, when the soil has warmed up a bit.

Prepare the soil by loosening it and removing any weeds. Sow seeds about ½ inch deep, spacing them 8-12 inches apart. Keep the soil consistently moist until the seedlings emerge. Direct sowing saves you the hassle of transplanting, but the plants may take a bit longer to bloom.

Calendula prefers moderate watering, but it's surprisingly tolerant of some drought, which is a plus in our dry Mountain climate. However, it can get stressed in peak summer heat.

Water deeply but infrequently, aiming for about 1 inch of water per week, depending on rainfall. Stick your finger about 2 inches into the soil – if it feels dry, it's time to water. Water at the base of the plant to avoid wetting the foliage, which helps prevent powdery mildew, though our low humidity usually keeps that in check.

Wilting leaves are a sign of underwatering, while yellowing leaves could indicate overwatering. Mulching around the plants with straw or wood chips helps retain moisture and regulate soil temperature, a lifesaver with our intense sun.

Deadheading is key to keeping your Calendula plants blooming throughout the season. Regularly remove spent flowers to encourage new buds. Simply snip off the flower heads just below the bloom.

If you want your Calendula to self-seed, leave a few flowers to mature and dry on the plant. They'll drop their seeds, giving you a head start for next year. As the first frost approaches in early September, you can let the remaining flowers go to seed or harvest them for medicinal or culinary use.

You can expect your first Calendula harvest in early July through mid September, about 45 days after planting. 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, leaving a short piece of stem attached. Harvesting regularly encourages the plant to produce more flowers. The petals are edible and can be used fresh or dried.

As the end of the season nears, harvest any remaining flowers before the first frost. You can dry them for later use or collect the seeds for next year's garden.

Calendula is generally pretty easy to grow, but here are a few common problems we see in the Mountain West:

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves and stems. Leaves may curl, yellow, and die.
• What causes it: Fungal disease that thrives in warm days, cool nights, and moderate humidity. Ironically, dry leaf surfaces favor it.
• How to fix/prevent it: Improve air circulation by spacing plants adequately. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help. A milk spray (1 part milk to 9 parts water) can also be surprisingly effective.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and undersides of leaves. Sticky honeydew residue. Distorted new growth.
• What causes it: Sap-sucking insects that reproduce rapidly, especially in warm weather. Ant colonies may protect them.
• How to fix/prevent it: Knock them off with a strong spray of water. Encourage beneficial insects like ladybugs. Insecticidal soap or neem oil can control heavy infestations. Avoid over-fertilizing with nitrogen.

Whiteflies

• What it looks like: Tiny white, moth-like insects that fly up when plants are disturbed. Yellowing or speckled leaves. Sticky honeydew.
• What causes it: Sap-sucking insects that thrive in warm, dry conditions.
• How to fix/prevent it: Hang yellow sticky traps to catch adults. Spray plants with insecticidal soap or neem oil, especially the undersides of leaves. Ensure good air circulation.

Mountain West Specific Challenges: Our intense sun can sometimes scorch Calendula leaves, so providing some afternoon shade can be helpful. The alkaline soil in many areas can also affect nutrient uptake, so amend the soil with compost before planting. Hail can be devastating, so consider using row covers or netting if hail is in the forecast.

Calendula makes a great companion plant in the Mountain West garden. It attracts beneficial insects and can help deter pests from other plants.

Good companions include tomatoes and peppers, as Calendula attracts pollinators and helps repel tomato hornworms and pepper weevils. Green beans also benefit from Calendula, which can deter bean beetles.

Avoid planting Calendula near members of the cabbage family, as it can attract cabbage moths. Otherwise, it's a pretty versatile and beneficial addition to the garden.