Chrysanthemum in Zone 8B — Pacific Northwest

Chrysanthemums are fantastic for adding late-season color to your Pacific Northwest garden. Their vibrant blooms brighten up the landscape just as other flowers start to fade, and they make stunning cut flowers to enjoy indoors. Plus, our cool nights here in the PNW actually intensify their colors, making them even more spectacular.

While we might get a later start than some regions, and our mild summers mean they need a little extra attention, Chrysanthemums thrive here if you time things right. With our 210-day growing season, you'll have plenty of time to enjoy their beauty.

Starting Chrysanthemums indoors isn't always necessary, especially since you can easily find healthy starts at local nurseries in spring or potted mums in fall. But, if you're eager to grow a specific variety or just love the process, starting indoors gives you a head start.

Begin in early to late February, about eight weeks before you plan to transplant them outdoors. Use seed trays with a good seed-starting mix and provide warmth (a heat mat helps) and plenty of light (grow lights are ideal, especially with our overcast spring days). Be sure to water from the bottom to avoid damping off.

Transplanting Chrysanthemums outdoors should happen in early April through early May, after the last expected frost. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight.

Space your plants 12-18 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast – those wet springs can bring unexpected chilly spells, so be ready to cover your young plants if needed. Buying starts from a local nursery is also a great option, giving you healthy, established plants ready to go.

Chrysanthemums need consistent moisture, but they don't like soggy feet, especially with our wet springs. The key is to water regularly at the base of the plant, avoiding wetting the foliage, which can encourage fungal diseases.

During the dry summer months, give them a good soak a couple of times a week, aiming for about 1 inch of water per week, depending on rainfall. Use the "finger test" – stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Overwatering can lead to root rot, while underwatering will cause the leaves to wilt and the buds to drop.

In the PNW, mulching around your plants with compost or shredded bark helps retain moisture and keeps the soil cool, which they appreciate during our mild summers.

Pinching your Chrysanthemums is essential for encouraging bushy growth and abundant blooms. Start when the plants are about 6 inches tall and pinch off the growing tips every 2-3 weeks through July 4th.

This encourages the plants to branch out, resulting in more stems and, therefore, more flowers. After July 4th, stop pinching to allow the flower buds to form. In late fall, after the first frost around early November, you can cut back the plants to a few inches above the ground.

You can expect your first Chrysanthemum blooms in mid-June through early August, depending on the variety and when you transplanted. The flowers last for weeks in the garden, providing a long season of color.

Cut the blooms for bouquets when the flowers are fully open, choosing stems with several open flowers and a few buds that are just starting to show color. Cut the stems at an angle and remove any leaves that will be below the waterline in your vase. Regularly deadhead spent flowers to encourage continued blooming.

As the first frost approaches in early November, you can cut the remaining flowers to enjoy indoors.

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 telltale signs.
• What causes it: These sap-sucking insects reproduce rapidly, especially during warm spells. Ants often "farm" them for their honeydew, protecting them from predators.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage natural predators like ladybugs and lacewings. For heavy infestations, use insecticidal soap or neem oil. Avoid over-fertilizing with nitrogen.

Spider Mites

• What it looks like: Fine stippling on leaves (tiny white dots), fine webbing on leaf undersides and between stems, and leaves that turn bronze or yellow.
• What causes it: These tiny arachnids thrive in dry conditions, making them more prevalent during our dry summer months.
• How to fix/prevent it: A strong spray of water, daily for a week, is often enough. Increase humidity around the plants. Neem oil or insecticidal soap can also help. Consider releasing predatory mites.

Leaf Miners

• What it looks like: You'll see winding, white or yellow tunnels within the leaves. These are the paths the larvae create as they feed.
• What causes it: These are the larvae of small flies, moths, sawflies, or beetles that lay their eggs on plant leaves. When the larvae hatch, they tunnel into the leaves to feed.
• How to fix/prevent it: Remove and destroy affected leaves as soon as you see the tunnels. For severe infestations, you can use insecticidal soap or neem oil, but be sure to follow the instructions carefully. Covering your plants with row covers can prevent the adult insects from laying eggs on the leaves in the first place.

Rust

• What it looks like: Rusty orange, yellow, or brown pustules on leaves and stems, mostly on the undersides. Leaves may yellow and drop prematurely.
• What causes it: Various rust fungi spread via wind-borne spores and thrive in warm, humid conditions with moisture on the leaves.
• How to fix/prevent it: Remove and destroy affected leaves. Avoid overhead watering and improve air circulation around your plants. Apply sulfur or copper fungicide if needed. Don't work among wet plants, and rotate crops to prevent the fungus from building up in the soil.

Pacific Northwest Specific Challenges: Although late blight isn't a primary concern for Chrysanthemums, our cool, wet springs can create favorable conditions for fungal diseases if you're not careful with watering. The dry summer months can also stress the plants if you don't provide consistent moisture.

Chrysanthemums make great companions for tomatoes and peppers. Their scent helps repel some common pests that bother these veggies, plus they attract pollinators, which is always a bonus. They also work well with lettuce since they provide some shade during the mild summer months.

Avoid planting them near anything in the *Brassica* family (like cabbage, broccoli, or kale). These plants can compete for nutrients and attract pests that may also bother your Chrysanthemums.