Cabbage in Zone 10B — Southern California

Cabbage is a fantastic addition to the Southern California garden, offering crisp, homegrown flavor that's far superior to store-bought. Imagine fresh coleslaw or stir-fries made with cabbage you nurtured yourself, a truly rewarding experience. Plus, it thrives in our mild winters, providing a harvest when other crops might be slowing down.

While our region presents challenges like drought and the occasional heat wave, careful timing allows you to enjoy a successful cabbage crop. With our long, 355-day growing season, you can easily work around the harsher periods and take advantage of the cooler months to grow this cool-season favorite.

Starting cabbage indoors gives you a head start (pun intended!) on the growing season here in Southern California. Aim to sow your seeds indoors from early to late November, about six weeks before you plan to transplant them. This timing takes advantage of our very-early spring character.

Use seed trays or small pots filled with a good seed-starting mix. Keep the soil consistently moist, and provide warmth and bright light, either from a sunny window or a grow light. Bottom watering is especially helpful at this stage to prevent damping off; simply set the tray in a shallow dish of water and let the soil soak it up.

Transplant your cabbage seedlings outdoors from late December through late January. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This prevents shock and helps them adjust to the Southern California elements.

When transplanting, space your cabbage plants 12 to 18 inches apart in a sunny spot with well-drained soil. Keep an eye on the forecast for any unexpected cold snaps, and be prepared to cover your young plants if necessary.

Consistent watering is key for healthy cabbage growth, especially since they aren't drought-tolerant. In Southern California, the weather dictates the watering schedule. During our winter-wet season, you might not need to water at all, relying instead on natural rainfall.

Once the weather warms up, especially as we head towards spring, check the soil moisture regularly using the "finger test" – stick your finger about two inches deep into the soil. If it feels dry, it's time to water. Aim for about 1-1.5 inches of water per week, watering deeply at the base of the plants to avoid wetting the foliage and encouraging fungal diseases in our low-to-moderate humidity.

Watch out for signs of underwatering, like wilting or stunted growth, and overwatering, like yellowing leaves. Adding a layer of mulch around your cabbage plants helps to retain moisture in the soil, which is especially important during drier periods and those Santa Ana winds.

You can expect to harvest your cabbage from early March through late April, about 70 days after transplanting. The best indicator of ripeness is the firmness of the head. Gently squeeze the cabbage head; it should feel solid and dense.

Once the head is firm and has reached a good size for its variety, use a sharp knife to cut it off at the base of the plant. Don’t pull or yank, as this can damage the roots. As our first frost approaches around late December, harvest any remaining heads, even if they're on the smaller side. They won't improve much after that point.

Here are some common cabbage problems in Southern California:

Cabbage Worms

• What it looks like: Smooth green caterpillars on brassica leaves. Irregular holes chewed in leaves. Dark green droppings. White butterflies hovering around plants.
• What causes it: Larvae of white cabbage butterflies. Multiple generations per season in our warm climate.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent egg laying. Handpick caterpillars. Interplant with aromatic herbs (thyme, sage). Encourage parasitic wasps.

Cabbage Loopers

• What it looks like: Similar to cabbage worms, but these caterpillars move in a looping motion. They also chew holes in leaves.
• What causes it: These are the larvae of a moth. They thrive in warm weather.
• How to fix/prevent it: Bt spray works well on loopers, too. Handpicking is also an option. Keep your garden free of weeds that can harbor these pests.

Splitting

• What it looks like: The cabbage head cracks open.
• What causes it: Inconsistent watering, especially heavy watering after a dry spell. The rapid water uptake causes the head to expand too quickly.
• How to fix/prevent it: Water regularly and consistently. Mulch around the plants to help retain moisture. Harvest heads as soon as they mature to prevent them from splitting.

Clubroot

• What it looks like: Stunted growth, wilting in afternoon heat, yellowing leaves. Roots are swollen, distorted, and club-shaped when dug up.
• What causes it: Soil-borne pathogen (Plasmodiophora brassicae) that persists in soil for 10+ years. Favors acidic, wet soil.
• How to fix/prevent it: Raise soil pH to 7.0-7.2 with lime. Improve drainage. Rotate brassicas on a 7-year cycle. Remove and destroy infected plants (don't compost). Start transplants in sterile mix.

Southern California Specific Challenges: Our hot summer heat inland can stress cabbage plants, making them more susceptible to pests and diseases. Water restrictions require careful monitoring and efficient watering practices. Santa Ana winds can quickly dry out the soil, so consistent moisture is crucial.

Companion planting can really help your cabbage thrive here in Southern California. Green beans are a great companion because they fix nitrogen in the soil, which cabbage loves. Celery helps to repel cabbage white butterflies, reducing the risk of cabbage worms. Onions and dill also deter pests and can improve the overall health of your cabbage. Potatoes are also good companions, as they don't compete for the same nutrients.

Avoid planting cabbage near tomatoes, strawberries, or peppers. Tomatoes and strawberries can attract pests that also affect cabbage. Peppers can stunt the growth of cabbage due to shared nutrient needs.