Collard Greens in Zone 10B — Southern California

Collard greens are a fantastic addition to your Southern California garden, offering a slightly bitter, earthy flavor that’s delicious in everything from Southern-style cooking to stir-fries. Plus, the satisfaction of harvesting fresh greens from your own backyard, even during our mild winters, is hard to beat.

While we face drought and occasional heat waves, collard greens are surprisingly adaptable with the right timing. Our long growing season, nearly year-round, gives you plenty of opportunities to cultivate a healthy crop.

Starting collard greens indoors in Southern California is an option, but not always necessary given our mild climate. If you want a head start, begin sowing seeds indoors from early to late December, about four weeks before you plan to transplant them.

Use seed trays or small pots filled with seed-starting mix, keep them consistently moist (bottom watering helps prevent damping off), and provide a warm location with plenty of light. Since we often get a very-early spring warmth in Southern California, starting indoors buys you some time.

Transplant your collard greens seedlings outdoors from early January through early February. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week.

Choose a spot with full sun to partial shade, and space plants 18-24 inches apart. Keep an eye on the weather forecast; even though our winters are mild, occasional cold snaps can stress young transplants.

Direct sowing collard greens works well in our Southern California climate, giving the plants a strong start. Sow seeds directly into the garden from late December through early October.

Prepare the soil by loosening it and mixing in compost. Sow seeds about ½ inch deep, spacing them 18-24 inches apart. Keep the soil consistently moist until seedlings emerge. Direct sowing avoids transplant shock and lets the roots develop undisturbed.

Collard greens need consistent moisture to produce tender, flavorful leaves, but they aren't drought-tolerant, so here's how to handle watering in our SoCal climate. During the cooler, winter-wet months, you might only need to supplement rainfall.

Once the weather warms up, especially during our hot summers, increase watering to about 1-1.5 inches per week. Use the "finger test" – if the top 2 inches of soil feel dry, it's time to water. Water deeply at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our low-to-moderate humidity.

Watch for signs of underwatering, like wilting or yellowing leaves, and overwatering, like root rot or leaf edema. Mulching around your collard greens with organic matter like compost or straw helps retain moisture and regulate soil temperature, crucial during our hot inland summers and Santa Ana winds.

You can expect your first harvest of collard greens from mid-March through early January, about 75 days after sowing. Look for lower leaves that are 10-12 inches long.

Harvest by cutting the outer leaves near the base of the plant, leaving the top rosette to continue growing. This allows for continuous production throughout the season. The flavor of collard greens often sweetens after a light frost, so don't be afraid to leave them in the garden as late December approaches.

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

Cabbage Worms

• What it looks like: Smooth green caterpillars chewing irregular holes in leaves, leaving dark green droppings. You might also see white cabbage butterflies fluttering around.
• What causes it: These are the larvae of white cabbage butterflies, which can have multiple generations in our long, warm season.
• How to fix/prevent it: Bt spray is very effective. You can also use floating row covers to prevent butterflies from laying eggs. Handpicking caterpillars and interplanting with aromatic herbs can also help.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. Sticky honeydew residue and curled or distorted new growth are also common.
• What causes it: Aphids are sap-sucking insects that reproduce rapidly, especially in warm weather. Ant colonies may "farm" them for their honeydew.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage natural predators like ladybugs and lacewings. Insecticidal soap or neem oil can be used for heavy infestations. Avoid excess nitrogen fertilizer, which attracts them.

Cabbage Loopers

• What it looks like: (This section was incomplete in the source data.)
• What causes it: (This section was incomplete in the source data.)
• How to fix/prevent it: (This section was incomplete in the source data.)

Downy Mildew

• What it looks like: Yellow patches on leaf tops with fuzzy gray-purple growth on undersides. Leaves brown and die from the bottom up.
• What causes it: A pathogen that spreads in cool, humid conditions via wind-carried spores.
• How to fix/prevent it: Remove affected leaves immediately and improve air circulation. Water at the base of the plants, never overhead. Copper-based fungicides can be used for prevention.

Southern California Specific Challenges: Our hot summer heat inland and occasional Santa Ana winds can stress collard greens, making them more susceptible to pests and diseases. Consistent watering and providing some afternoon shade during the hottest months can help. Also, be mindful of water restrictions and adjust your watering schedule accordingly, prioritizing early morning watering to minimize evaporation.

Companion planting can greatly benefit your collard greens in Southern California. Plant onions and garlic nearby to deter pests with their strong scent. Beets are good companions as they don't compete for the same nutrients and can help improve soil structure. Potatoes also make good neighbors, as they don't attract the same pests. Dill attracts beneficial insects that prey on common collard green pests.

Avoid planting strawberries or tomatoes near your collard greens. Strawberries are susceptible to similar fungal diseases, increasing the risk of spreading them. Tomatoes can attract pests that also affect collards.