Cabbage in Zone 10A — Southern California

Cabbage thrives in our mild winters, offering a satisfying year-round harvest potential unique to Southern California. Imagine crisp, homegrown cabbage in your slaws, stir-fries, and soups, all thanks to our long growing season and the plant's frost tolerance.

Sure, we face drought and occasional heat waves, but with careful timing and water-wise gardening practices, you can absolutely enjoy a successful cabbage crop. Our 349-day growing season gives you the flexibility to work around those challenges and enjoy fresh cabbage from your own backyard.

For a spring cabbage harvest, start your seeds indoors from mid-November through early December. This gives the seedlings about 6 weeks to get a head start before transplanting. Use seed trays or small pots filled with a good seed-starting mix.

Keep the trays in a warm spot, around 70°F, and provide plenty of light – a grow light works wonders. Be sure to water from the bottom to encourage strong root growth and prevent damping-off. Given our very-early spring character, this indoor start is key to getting a jump on the season.

Transplant your cabbage seedlings outdoors from early to late January, once they have a few sets of true leaves. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This prevents transplant shock.

Space the seedlings about 12-18 inches apart in well-drained soil. Even in January, we can experience warm spells, so make sure the soil stays consistently moist after transplanting to help them settle in.

Cabbage needs consistent moisture to thrive, but overwatering can be just as detrimental, especially with our winter-wet rainfall. Aim for moderate watering, and remember that Southern California's climate can be unpredictable.

During the cooler months, check the soil moisture about 2 inches deep using the "finger test." If it feels dry, it's time to water. Water deeply at the base of the plant, providing about 1 inch of water per week, depending on rainfall. Avoid overhead watering to minimize fungal diseases in our low-to-moderate humidity.

Inland, during warmer spells, you might need to water more frequently. Signs of underwatering include wilting leaves, while yellowing leaves can indicate overwatering. Mulching around your cabbage plants helps retain moisture and regulate soil temperature, which is especially helpful during our hotter periods and fire season.

Your first cabbage harvest should be ready from mid-March through late April, about 70 days after transplanting. The key indicator is the firmness of the head. Gently squeeze the cabbage head; it should feel solid and dense.

Once it's firm and has reached the full size for its variety, use a sharp knife to cut the head at the base of the plant. Leave the roots in the ground, as they can sometimes produce smaller side shoots. As late December approaches, harvest any remaining heads before potential frost, although cabbage is fairly frost-tolerant.

Here are some common problems you might encounter growing cabbage in Southern California:

• Cabbage Worms
• What it looks like: Smooth green caterpillars chewing irregular holes in leaves, leaving dark green droppings. You'll see white butterflies fluttering around.
• What causes it: These are the larvae of cabbage butterflies, which thrive in our long, warm growing season and can have multiple generations.
• How to fix/prevent it: Bt spray is highly effective. Use floating row covers to prevent butterflies from laying eggs. Handpick the caterpillars. Interplant with aromatic herbs like thyme and sage to deter them. 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: Another type of caterpillar that enjoys brassicas. They flourish in our mild climate.
• How to fix/prevent it: Similar to cabbage worms – Bt spray, row covers, handpicking, and attracting beneficial insects.
• Splitting
• What it looks like: The cabbage head cracks open.
• What causes it: Inconsistent watering. Heavy watering after a dry spell causes the head to grow too quickly and split.
• How to fix/prevent it: Maintain consistent soil moisture. Mulch to help regulate soil moisture. Harvest promptly when heads are mature.
• Clubroot
• What it looks like: Stunted growth, wilting in the afternoon heat, and yellowing leaves. Dig up the plant, and you'll see swollen, distorted, club-shaped roots.
• What causes it: A soil-borne pathogen that loves acidic, wet soil and can persist for years.
• How to fix/prevent it: Raise the soil pH to 7.0-7.2 with lime. Improve drainage. Rotate your brassicas on a 7-year cycle. Remove and destroy infected plants (don't compost them). Start transplants in sterile potting mix.

Southern California Specific Challenges: Our hot summer heat inland can stress cabbage, making them more susceptible to pests and diseases. Low-to-moderate humidity generally helps prevent fungal issues, but consistent watering is crucial to avoid splitting, especially after our winter rains.

Companion planting can give your cabbage a boost in Southern California.

• Good companions: Green beans fix nitrogen in the soil, benefiting cabbage. Celery deters cabbage moths. Onions repel many pests. Potatoes don't compete for nutrients and can help break up the soil. Dill attracts beneficial insects that prey on cabbage pests.
• Bad companions: Tomatoes, strawberries, and peppers can stunt cabbage growth. They compete for the same nutrients and can attract similar pests.