Calendula in Zone 8A — Pacific Northwest

Calendula is a fantastic addition to any Pacific Northwest garden. Its bright, cheerful blooms are not just pretty faces; the petals are edible and have medicinal properties. Plus, Calendula thrives in our mild summers and cool nights, bringing a splash of color to your garden from spring through fall, and attracting beneficial insects.

While we might not have the long, scorching summers of other regions, Calendula is well-suited to our 203-day growing season. With a little attention to timing, you can enjoy a continuous harvest of flowers. The wet springs can be a challenge, but proper soil and spacing can help you overcome them.

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. If you want to start them indoors, aim for early to late February, about six weeks before you plan to transplant.

Use seed trays with a good seed-starting mix. Keep them in a warm spot (around 70°F) with plenty of light – a sunny windowsill or grow lights will do the trick. Bottom watering is a great way to prevent damping-off, which can be a problem during our overcast spring days.

Transplant your Calendula seedlings outdoors from late March through early May, once the danger of hard frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and brighter sunlight.

Choose a sunny spot with well-drained soil. Space the plants about 8-12 inches apart to allow for good air circulation. Keep an eye on the weather forecast; a late cold snap can still happen, so be prepared to cover your seedlings if needed.

Direct sowing Calendula is a simple and effective method, especially since our springs tend to be wet. Sow seeds directly into the garden from late March through early September. This gives you a long window for staggered plantings and continuous blooms.

Prepare the soil by loosening it and removing any weeds. Calendula seeds germinate best in soil that's at least 60°F. Sow the seeds about ¼ inch deep and 8-12 inches apart. Keep the soil consistently moist until the seedlings emerge, which usually takes about a week.

Calendula prefers moderate watering, but it's surprisingly tolerant of short periods of drought, which can happen during our dry summer months. However, unlike other regions, you rarely need to supplement rainfall in the PNW except during the driest parts of July and August.

During the wet springs, be careful not to overwater. Check the soil moisture by sticking your finger about 2 inches deep. If it feels wet, hold off on watering. Aim for about 1 inch of water per week during the dry months, either from rainfall or irrigation.

Water at the base of the plants rather than overhead to avoid fungal diseases, especially during our humid spring and fall. Overwatering can lead to root rot, indicated by yellowing leaves and stunted growth. Underwatering will cause the leaves to wilt and the plant to stop blooming. A layer of mulch, like composted leaves, can help retain moisture and suppress weeds.

Regular deadheading is key to keeping your Calendula blooming throughout the season. Simply pinch or cut off the spent flowers just below the flower head. This encourages the plant to produce more blooms instead of setting seed.

You can deadhead from mid-May through late October. If you want Calendula to self-seed, leave a few flowers to mature and dry on the plant. As the first frost approaches in late October, you can let the remaining flowers go to seed for next year.

You can expect your first Calendula harvest around mid-May if you start seeds early, and continue harvesting through early November. The flowers are ready to harvest when they are fully open and the petals are vibrant.

To harvest, simply cut the flower heads off with scissors or snips. Handle them gently to avoid bruising the petals. Harvest in the morning after the dew has dried for the best flavor and medicinal properties.

For continuous production, harvest flowers regularly. As the end of the season nears and the first frost approaches in late October, harvest any remaining flowers to dry for later use.

Here are some problems to watch out for with Calendula in the Pacific Northwest:

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems. Leaves curl, yellow, and die.
• What causes it: Fungi thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces favor it. This is common during late summer and early fall in the PNW as the days shorten and humidity increases.
• How to fix/prevent it: Improve air circulation by spacing plants properly and pruning. Remove affected leaves. Neem oil or potassium bicarbonate sprays can help. Milk spray (1 part milk to 9 parts water) is 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. While our summers are mild, aphids can still become a problem, especially during dry spells.
• 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.

Whiteflies

• What it looks like: Tiny white, moth-like insects that fly up when disturbed. Yellowing and sticky leaves. Stunted growth.
• What causes it: Sap-sucking insects that thrive in warm, sheltered environments. They can be a nuisance in greenhouses or during unusually warm summers in the PNW.
• How to fix/prevent it: Yellow sticky traps can catch adult whiteflies. Strong water spray can dislodge them from plants. Insecticidal soap or neem oil can control infestations. Ensure good air circulation.

Pacific Northwest Specific Challenges: Our mild heat and dry-summer humidity can create ideal conditions for powdery mildew on Calendula, especially in late summer. Monitor your plants closely and take preventative measures early. Slugs can also be a problem, especially for young seedlings. Use slug bait or traps to protect your plants.

Calendula makes a great companion plant in the Pacific Northwest garden. Plant it near tomatoes and peppers to attract beneficial insects like hoverflies and ladybugs, which prey on aphids and other pests. These insects help keep those crops healthy.

Calendula also does well near green beans. It attracts pollinators, increasing bean production. Avoid planting Calendula near plants in the cabbage family (broccoli, kale, cabbage) as they compete for the same nutrients.