Calendula in Zone 8B — Pacific Northwest

Calendula is a fantastic flower to grow in our Pacific Northwest gardens. The petals add a pop of color to salads, can be used in homemade skincare, and are simply cheerful. The satisfaction of harvesting armfuls of sunny blooms from spring through fall is hard to beat, especially with our cool nights enhancing their fragrance.

We do face some unique challenges here in the PNW, like cool soil in spring and the occasional bout of powdery mildew. But with our long, mild growing season of around 210 days, and by choosing the right varieties and timing, you can easily enjoy a thriving Calendula patch.

Starting Calendula indoors is certainly an option, especially if you're eager to get a jump start on the season. Start your seeds indoors from early to late February, about six weeks before you plan to transplant them outside. This is especially useful if our spring is slower than usual.

Use seed trays with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light, either from a sunny windowsill or a grow light. Remember to water from the bottom to prevent damping-off. Keep in mind that Calendula germinates easily outdoors once the soil warms up a bit, so indoor starting isn't always necessary.

Transplant your Calendula seedlings outdoors from late March through early May, once the danger of a 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 cooler temperatures and stronger sunlight.

Space your Calendula plants 8-12 inches apart in a sunny spot. Our overcast spring days can sometimes linger, so choose a location that gets as much sun as possible. Be mindful of slugs, which love tender young seedlings!

Direct sowing Calendula is a breeze in our climate, and often the easiest method. Sow seeds directly into the garden from late March through early September. This gives you a long window for succession planting and a continuous supply of blooms.

Prepare the soil by loosening it and removing any weeds. Calendula isn't too picky about soil, but it appreciates good drainage. Sow seeds about 1/4 inch deep and space them 8-12 inches apart. Keep the soil consistently moist until the seedlings emerge.

Calendula needs moderate watering, especially during its active growth periods. While it can tolerate some drought once established, consistent moisture encourages more blooms. Our dry-summer climate means you'll need to pay attention to watering, especially during those drier months.

During the wet springs, you might not need to water much at all. Once the dry summer months arrive, check the soil moisture regularly. 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.

Water at the base of the plants to avoid wetting the foliage, which can encourage powdery mildew in our sometimes humid conditions. Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to root rot, so make sure the soil is well-draining. A layer of mulch, like composted leaves or bark chips, will help retain moisture and suppress weeds.

Deadheading is key to 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 base of the flower.

Deadheading can be done anytime from early May through late October. Leave some flowers to mature at the end of the season if you want them to self-seed for next year. Before the first frost around early November, you can cut back the plants to tidy them up, or leave them standing for winter interest.

You can expect your first Calendula harvest about 45 days after planting, usually from early May through early November. Harvest the flowers when they are fully open and the petals are at their peak color. The petals are most flavorful and have the highest medicinal properties at this stage.

To harvest, simply snip off the flower heads with scissors or pruners. Be careful not to damage the surrounding foliage. Regular harvesting encourages the plant to produce more flowers, so keep at it!

As the first frost approaches in early November, harvest any remaining flowers. You can dry them for later use. You can also collect the seeds from the dried flower heads to sow next year.

Here are a few common problems you might encounter with Calendula in the Pacific Northwest:

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes flower buds. Leaves can curl, yellow, and eventually die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Ironically, dry leaf surfaces favor it. Our late summer and early fall conditions can be perfect for powdery mildew.
• 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 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, though they can be present most of the season. Ants often farm them for their honeydew.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap is effective for heavy infestations. Neem oil works systemically.

Whiteflies

• What it looks like: Tiny white, moth-like insects that fly up when disturbed. Yellowing or silvering of leaves. Sticky honeydew residue.
• What causes it: Sap-sucking insects that thrive in warm, sheltered conditions. They can quickly build up large populations.
• How to fix/prevent it: Yellow sticky traps can capture adults. Insecticidal soap or neem oil can help control infestations. Strong water sprays can dislodge them. Encourage beneficial insects like lacewings and parasitic wasps.

Pacific Northwest Specific Challenges: Our mild summers and dry-summer climate generally benefit Calendula. However, our cool, wet springs can make seedlings vulnerable to slugs. Keep an eye out for these pests and take appropriate measures. Late blight is not typically a problem for Calendula itself, but good garden hygiene practices can prevent its spread to other susceptible plants like tomatoes.

Calendula makes a great companion plant in the Pacific Northwest garden. Plant it near tomatoes and peppers, as it attracts beneficial insects that prey on aphids and other pests that can bother those veggies. Calendula also helps deter tomato hornworms.

Calendula is a good companion to green beans, as it can help repel bean beetles. There aren't any specific plants to avoid planting near Calendula.