Chrysanthemum in Zone 8B — Southern California

Chrysanthemums are a fantastic addition to any Southern California garden, bringing vibrant color and classic beauty. Their blooms provide a welcome burst of life, perfect for bouquets and adding cheer to your outdoor space. Plus, they're relatively easy to grow here with our long, warm season, making them a rewarding choice for both beginner and experienced gardeners.

We definitely face our share of challenges in SoCal, from drought and water restrictions to intense summer heat, especially inland. But with careful planning and attention to watering, you can successfully grow chrysanthemums. Our 298-day growing season offers plenty of time for them to thrive.

Starting chrysanthemum seeds indoors isn't essential in our climate, but it can give you a head start, especially if you want specific varieties not readily available as starts. If you choose to go this route, begin in mid December through early January, roughly 8 weeks before you'd like to transplant them outdoors.

Use seed trays with a good seed-starting mix, providing warmth (a heat mat helps) and plenty of light – a grow light is ideal. Water from the bottom to prevent damping off. Given our very-early spring character here in Southern California, getting a jump start indoors allows you to enjoy earlier blooms.

Transplant your chrysanthemum seedlings outdoors from mid February through mid March. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Space them 12-18 inches apart in well-draining soil. Be mindful of late-season temperature swings we can experience. Water them in well after transplanting. Buying potted mums in the fall, or spring starts, is a great option to simplify growing.

Chrysanthemums need consistent moisture, but they don't like soggy soil. During our hot, dry summers, you'll likely need to water them deeply a couple of times a week. The "finger test" is your best friend: stick your finger about 2 inches into the soil. If it feels dry, it's time to water.

Aim for about 1 inch of water per week, delivered at the base of the plant to avoid wetting the foliage and encouraging fungal diseases. Remember, we have low-to-moderate humidity here, so overhead watering isn't ideal. In our winter-wet season, reduce watering accordingly.

Signs of underwatering include wilting leaves and dry soil. Overwatering can lead to yellowing leaves and root rot. A layer of mulch around the base of the plants will help retain moisture and keep the soil cool, especially helpful during our summer heat inland.

Pruning chrysanthemums is key to getting those beautiful, bushy plants packed with flowers. Start pinching off the growing tips of the stems every 2-3 weeks, beginning when the plants are about 6 inches tall. Do this consistently through July 4th.

Pinching encourages branching and more blooms. After July 4th, stop pinching, as the plants need time to set their flower buds for fall blooming. As the first frost approaches around early December, you can cut back the plants to a few inches above the ground to prepare them for winter dormancy.

You can expect your first chrysanthemum harvest from late April through mid June, depending on when you transplanted and the specific variety. The best time to harvest is when the flowers are fully open and showing their vibrant colors. These flowers can last for weeks in the garden.

To harvest, simply cut the stems at an angle, leaving a good amount of foliage on the plant to encourage continued production. Regular harvesting will encourage more blooms throughout the season. Even as the first frost approaches in early December, you can still enjoy the last of your blooms indoors by bringing cut flowers inside.

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. Curled or distorted new growth. *What causes it:* Rapid-reproducing sap-sucking insects. Populations explode in warm weather, especially during our long summers. 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 our frequent periods of 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:* *What causes it:* *How to fix/prevent it:*

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 (though we don't often have humid). *How to fix/prevent it:* Remove affected leaves immediately. 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 summer heat, particularly inland, can stress chrysanthemums, making them more susceptible to spider mites and aphids. Low-to-moderate humidity can also favor spider mite infestations. While our winter-wet rainfall is welcome, it can also create conditions for rust if air circulation is poor. Be vigilant and adjust your watering and pest control practices accordingly.

Chrysanthemums benefit from companion planting. Tomatoes and peppers are good companions because they deter pests that might attack your mums. The strong scent of these plants can confuse or repel aphids and other insects.

Lettuce also makes a good companion, acting as a ground cover to help retain moisture in the soil and suppress weeds, which is especially helpful during our drier months. Avoid planting chrysanthemums near plants that are susceptible to fungal diseases, as this could increase the risk of rust, especially during our occasional humid spells.