Calendula in Zone 7A — Pacific Northwest

Calendula is a fantastic addition to any Pacific Northwest garden. The bright, cheerful blooms add a splash of color, and the petals are edible, adding a peppery note to salads. Plus, the cool nights we often experience seem to enhance the flavor. You'll find a lot of satisfaction growing this versatile plant.

While we have mild summers in the PNW, we also have our share of gardening challenges, like cool soil in spring and slugs. But with careful timing and a little planning, Calendula thrives here. Our 183-day growing season gives you ample opportunity to enjoy its beauty and benefits.

Starting Calendula indoors isn't strictly necessary in our climate, but it can give you a head start, especially if you're eager for early blooms. Starting seeds indoors from mid February through early March allows you to get a jump on the season.

Use seed trays with a good seed-starting mix and provide gentle bottom watering to avoid damping off. A heat mat can help speed up germination, and once the seedlings emerge, make sure they have plenty of light, especially with our often overcast spring days.

Transplant your Calendula seedlings outdoors from early April through mid May, once the danger of hard frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week.

Space your plants 8-12 inches apart to allow for good air circulation, which is important for preventing powdery mildew. Keep an eye on the weather forecast, as we can still get some chilly snaps in early spring, and protect your young plants if needed.

Direct sowing Calendula is a simple and effective method in the PNW. You can sow seeds directly into the garden from early April through late August. Direct sowing is especially helpful for a continuous bloom throughout the summer and into fall.

Choose a sunny spot with well-drained soil. Prepare the soil by loosening it and removing any weeds. Sow the seeds about ¼ inch deep and 8-12 inches apart. Keep the soil consistently moist until the seedlings emerge.

Calendula prefers moderate watering, which aligns well with our typical PNW rainfall patterns. During the wet springs, you might not need to water at all. However, during the dry summer months, consistent moisture is key.

Check the soil moisture by using the "finger test"—stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Aim for about 1 inch of water per week, either from rainfall or irrigation. Watering at the base of the plant helps prevent fungal diseases, which can be a concern even with our dry-summer humidity.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to root rot, indicated by yellowing leaves and a generally unhealthy appearance. A layer of mulch can help retain moisture and regulate soil temperature, which is especially beneficial during our occasionally warm spells.

Deadheading is crucial for keeping your Calendula plants blooming throughout the season. Regularly remove spent flowers to encourage the plant to produce more buds. Simply snip off the flower heads just below the bloom.

You can deadhead anytime throughout the growing season, from late spring through fall. Towards the end of the season, around our first frost in mid- October, you can let some of the flowers mature and set seed if you want them to self-sow or if you want to collect seeds for next year.

You can expect your first Calendula harvest about 45 days after planting, typically from late May through late October in the PNW. Harvest the flowers when they are fully open and the petals are vibrant.

To harvest, simply snip off the entire flower head. This encourages the plant to produce more blooms. You can use the fresh petals in salads or dry them for medicinal purposes.

To encourage continuous production, harvest regularly. As the first frost approaches in mid- October, harvest any remaining flowers. You can also allow some of the last blooms to go to seed if you want them to naturalize in your garden.

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

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes flower buds. Leaves may curl, yellow, and eventually die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it. This means even with our dry summers, the cool nights can create ideal conditions.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can 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 may be present. New growth might appear curled or distorted.
• What causes it: Rapidly reproducing sap-sucking insects. Populations can explode during warmer periods. Ant colonies may farm them for honeydew.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage natural predators like ladybugs and lacewings. Insecticidal soap is effective for heavy infestations, and neem oil works systemically. Avoid over-fertilizing with nitrogen, which attracts them.

Whiteflies

• What it looks like: Tiny, white, moth-like insects that flutter around the plant when disturbed. Yellowing or silvering of leaves. Sticky honeydew.
• What causes it: These sap-sucking insects thrive in warm, sheltered conditions. They can quickly multiply and weaken plants.
• How to fix/prevent it: Yellow sticky traps can capture adult whiteflies. Spray plants with insecticidal soap, making sure to cover the undersides of leaves. Encourage natural predators like lacewings and parasitic wasps.

Pacific Northwest Specific Challenges: While Calendula is relatively resilient, our mild heat and dry-summer rainfall can still present challenges. Powdery mildew can be a concern, especially during periods of fluctuating temperatures. Slugs can also be an issue, especially with young seedlings. Keep an eye on your plants and address any problems promptly to ensure a healthy and abundant harvest.

Calendula makes a great companion plant in the Pacific Northwest garden. Planting Calendula near tomatoes and peppers can help deter pests like aphids and whiteflies, protecting your precious warm-season crops that sometimes struggle with our shorter summers. Green beans also benefit, as Calendula attracts beneficial insects that prey on bean pests.