Chrysanthemum in Zone 7B — Northern California

Chrysanthemums bring a welcome burst of color to the garden, especially as the days get shorter here in Northern California. Their cheerful blooms make excellent cut flowers, and they're surprisingly easy to grow in our Mediterranean climate. Plus, they attract beneficial insects to your garden.

Our dry summers and occasional water restrictions can present a challenge, but with careful planning and attention to watering, you can absolutely enjoy these beauties. Our long 245-day growing season gives you plenty of time to get them established and blooming.

Starting chrysanthemum seeds indoors is an option, but honestly, it's often easier to buy starts from a local nursery, or potted mums in the fall. If you're set on starting from seed, aim for mid January through early February, about eight weeks before you intend to transplant outdoors.

Use seed trays with a good seed-starting mix, keep them consistently moist (bottom watering is great for this), and provide plenty of light – a grow light works well, especially with our early spring character. Keep the soil warm, around 70-75°F, until germination.

Transplant your chrysanthemum seedlings outdoors from mid March through mid April, after the last expected frost. Be sure to harden them off first – gradually expose them to outdoor conditions for about a week before planting.

Space them 12-18 inches apart in a sunny spot with well-draining soil. We can still get some chilly nights and unexpected rain during this period, so keep an eye on the forecast and be ready to cover them if needed. Buying potted mums in the fall to overwinter is also a good strategy.

Chrysanthemums need consistent moisture, especially during bud formation, but they definitely don't want to be waterlogged. In our Northern California climate, that means paying close attention to your watering schedule.

During the hotter summer months, especially with our dry summers, check the soil moisture regularly. Stick your finger about two inches deep – if it feels dry, it's time to water. Aim for about an inch of water per week, but adjust based on rainfall and temperature. Always water at the base of the plant to avoid wetting the foliage, which can lead to fungal diseases in our microclimates.

Signs of underwatering include wilting leaves and dry, crispy edges. Overwatering can cause yellowing leaves and root rot. Mulching around the base of the plant with compost or wood chips helps retain moisture and keeps the soil cool.

To encourage bushy plants with lots of flowers, pinch off the growing tips of your chrysanthemums every two to three weeks until July 4th. This encourages side shoots to develop, which means more blooms later on.

After July 4th, stop pinching so the plants can focus on developing flower buds. As the first frost approaches around mid- November, you can cut back the foliage to tidy up the plants.

You can expect your first chrysanthemum blooms from late May through mid July, depending on the variety and when you transplanted. The flowers last for weeks in the garden, providing a long season of color.

Cut the flowers for bouquets when they are fully open. Use sharp, clean snips to avoid damaging the plant. Deadheading spent blooms encourages continued production. As the first frost approaches in mid- November, cut any remaining flowers to enjoy indoors.

Here are some common problems you might encounter with chrysanthemums in Northern California:

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.
• 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. Avoid excess nitrogen fertilizer (it attracts them).

Spider Mites

• What it looks like: Fine stippling on leaves (tiny white dots). Fine webbing on leaf undersides and between stems. Leaves turn bronze or yellow.
• What causes it: Tiny arachnids that thrive in hot, dry conditions. Populations explode in drought stress.
• How to fix/prevent it: Strong water spray (daily for a week) is the best treatment. Increase humidity around plants. Neem oil or insecticidal soap. Release predatory mites (Phytoseiulus persimilis). Avoid broad-spectrum pesticides that kill predators.

Leaf Miners

• What it looks like: Tan, winding trails inside the leaves. Leaves may look blotchy and discolored.
• What causes it: Larvae of small flies that burrow between the leaf surfaces to feed.
• How to fix/prevent it: Remove and destroy affected leaves. Cover plants with row covers to prevent adult flies from laying eggs. Neem oil can help control infestations.

Rust

• What it looks like: Rusty orange, yellow, or brown pustules on leaves and stems, mostly on undersides. Leaves yellow and drop prematurely.
• What causes it: Various rust fungi that spread via wind-borne spores. Favored by warm, humid conditions with moisture on leaves.
• How to fix/prevent it: Remove affected leaves. Avoid overhead watering. Improve air circulation. Apply sulfur or copper fungicide. Don't work among wet plants. Rotate crops.

Northern California Specific Challenges: The combination of moderate-to-hot heat and low humidity during our dry summers can stress chrysanthemums, making them more susceptible to spider mites and other pests. Proper watering and good air circulation are key to keeping your plants healthy.

Chrysanthemums make good companions for tomatoes and peppers. They help repel some of the pests that bother these plants, and they also attract beneficial insects that can help with pollination.

Lettuce also benefits from being planted near chrysanthemums, as they provide some shade during the hottest part of the day, preventing bolting. Avoid planting chrysanthemums near , as they compete for nutrients and can attract pests that will also bother your mums.