Chrysanthemum in Zone 9A — Southern California

Chrysanthemums bring vibrant fall color to our SoCal gardens, just when many other blooms are fading. Their long-lasting flowers make stunning bouquets, and they're surprisingly easy to grow here, adding a burst of cheerfulness to your landscape. Plus, their late-season blooms are a welcome sight after a long, hot summer.

Our Mediterranean climate in Southern California, with its long growing season, allows you to cultivate Chrysanthemums for months of enjoyment. While we do face challenges like water restrictions and the occasional heat wave, careful planning and water-wise gardening practices will help you achieve a beautiful display during our 322-day growing season.

Starting Chrysanthemum seeds indoors gives you a head start, but honestly, it's often easier to buy established plants. However, if you're eager to try, sow seeds indoors from late November through late December, roughly eight weeks before transplanting. Use seed trays with a good seed-starting mix and provide warmth and plenty of light.

A helpful tip: bottom water your seed trays to prevent damping off and keep the seedlings consistently moist. Remember, our spring warmth arrives early in Southern California, so timing is important to get your plants established before it gets too hot inland.

The ideal time to transplant your Chrysanthemums outdoors is early February through early March. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sunshine and temperature fluctuations.

Space plants 12-18 inches apart to allow for good air circulation, crucial in our sometimes humid coastal areas. Buying established plants, either potted mums in the fall or starts in the spring, is also a great option for a quicker, easier display.

Chrysanthemums need consistent moisture, but they definitely don’t want to be waterlogged. In Southern California's climate, this means adjusting your watering schedule with the seasons. During our mild winters, rainfall might be enough, but check the soil moisture regularly.

From spring through our hot summers and into fall, water deeply at the base of the plant when the top two inches of soil feel dry to the touch – use the finger test. Aim for about 1 inch of water per week, more during heat waves. Water at the base to avoid wetting the foliage and potentially encouraging fungal diseases, which can be a problem even with our low-to-moderate humidity.

Signs of underwatering include wilting leaves and dry, crispy edges. Overwatering can lead to yellowing leaves and root rot. A layer of mulch around the base of your plants helps retain moisture and regulate soil temperature, a real benefit in our fluctuating SoCal climate.

To encourage bushy growth and abundant blooms, pinch back the growing tips of your Chrysanthemums every 2-3 weeks until July 4th. This promotes branching and results in more flowers. After July 4th, stop pinching to allow flower buds to form.

As the first frost approaches around mid- December, you can cut back the foliage to near ground level. This helps tidy up the garden and prepares the plant for its dormant period.

In Southern California, you can expect your first Chrysanthemum harvest from mid April through late May, depending on the variety and when you transplanted. The flowers last for weeks in the garden, providing a long-lasting display. Cut stems for bouquets when the flowers are fully open.

To harvest, use sharp, clean pruners to cut the stem at an angle, just above a leaf node. This encourages new growth and continued production. As the weather cools in late fall, you can still enjoy the blooms, extending the harvest season right up until our first frost, which usually hits around mid- December.

Here are some common problems you might encounter with Chrysanthemums in Southern California:

Aphids

• What it looks like: Clusters of tiny, soft-bodied insects (green, black, or white) on stems and leaf undersides. Sticky honeydew residue and curled or distorted new growth.
• What causes it: Rapid-reproducing sap-sucking insects that thrive 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 during drought stress, common in SoCal.
• 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, squiggly lines or blotches appear on leaves.
• What causes it: Larvae of small flies that tunnel between the upper and lower leaf surfaces. They can weaken plants and make them unsightly.
• How to fix/prevent it: Remove and destroy affected leaves immediately. Encourage beneficial insects like parasitic wasps. Cover plants with row covers to prevent flies from laying eggs. Insecticidal soap or 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.

Southern California Specific Challenges: Our hot summers, low-to-moderate humidity, and occasional Santa Ana winds can stress Chrysanthemums. Consistent watering, especially during heat waves, is crucial. Mulching helps retain moisture and regulate soil temperature. Be vigilant about checking for pests and diseases, and take action promptly to prevent infestations from spreading.

Chrysanthemums benefit from companion planting in our Southern California gardens. Tomatoes and peppers make good companions because they deter nematodes and other soil pests that can affect Chrysanthemums. Lettuce is another good choice, as it provides ground cover that helps keep the soil cool and moist, which Chrysanthemums appreciate, particularly during our warmer months.

Avoid planting Chrysanthemums near members of the Aster family, like sunflowers and asters, as they can compete for resources and attract similar pests and diseases. This helps maintain a healthy and productive garden, optimizing the benefits of our long growing season.