Collard Greens in Zone 9B — Southern California

Collard greens are a Southern staple that surprisingly thrive in our Southern California climate, offering a welcome taste of the South right in your backyard. Their robust flavor, especially after a touch of frost, makes them incredibly versatile in the kitchen – from braising and sautéing to adding a nutritious boost to soups and stews. Plus, the satisfaction of harvesting fresh greens throughout our long growing season is hard to beat.

While we face challenges like drought, occasional Santa Ana winds, and summer heat inland, strategic timing allows us to enjoy a bountiful collard harvest. Our 334-day growing season gives you ample opportunity to work around these potential issues and enjoy these nutritious greens.

Starting collard greens indoors in Southern California is an option, but honestly, it's usually not necessary given our mild winters and extended growing season. However, if you're aiming for a very early harvest, or if you just prefer a head start, you can begin indoors from late December through mid January, about four weeks before you'd like to transplant.

Use seed trays with a good seed-starting mix and provide consistent warmth and bright light, either from a sunny window or a grow light. Remember to water from the bottom to encourage strong root growth and prevent damping-off. With our very-early spring character, this can give you an edge.

Transplant your collard green seedlings outdoors from late January through late February. This timing allows them to establish themselves before the summer heat inland intensifies.

Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. Space them 18-24 inches apart in well-drained soil. At this time of year, keep an eye out for unexpected cold snaps, and be ready to protect your young plants with row covers if needed.

Direct sowing collard greens is a simple and effective method, especially considering our long growing season. You can direct sow from mid January through late September, giving you plenty of flexibility.

Prepare your soil by loosening it and amending with compost. Ensure the soil temperature is at least 60°F for optimal germination. Sow seeds ½ inch deep and space them 18-24 inches apart, thinning as needed once the seedlings emerge. Direct sowing bypasses the transplant shock and can result in stronger, more resilient plants.

Collard greens need consistent moisture to produce tender, flavorful leaves, but they aren't as drought-tolerant as some of our native plants. In Southern California, the watering schedule will vary depending on the season and rainfall.

During our winter-wet season, you might only need to supplement rainfall occasionally. As the weather warms up in spring and summer, increase watering to 1-2 inches per week, especially during periods of low rainfall and summer heat inland. Use the "finger test" – if the top 2 inches of soil are dry, it's time to water.

Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our low-to-moderate humidity. Signs of underwatering include wilting leaves, while yellowing leaves can indicate overwatering. A layer of mulch around your plants will help retain moisture and keep the soil cool, which is especially helpful during Santa Ana winds and fire season.

You can expect your first collard green harvest from late March through early January, about 75 days after planting. Look for lower leaves that are 10-12 inches long and a deep green color.

To harvest, simply cut the outer leaves near the base of the plant, leaving the top rosette intact to continue growing. This allows for a continuous harvest throughout the season. In Southern California, the flavor of collard greens often sweetens after a light frost, so don't be afraid to leave them in the ground as late December approaches.

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

Cabbage Worms

• What it looks like: Smooth green caterpillars chewing irregular holes in leaves, dark green droppings, white butterflies flying around.
• What causes it: Larvae of white cabbage butterflies, with multiple generations in our warm climate.
• How to fix/prevent it: Bt spray is very effective. Use floating row covers to prevent butterflies from laying eggs. Handpick caterpillars and interplant with aromatic herbs.

Aphids

• What it looks like: Clusters of tiny insects (green, black, or white) on stems and leaf undersides, sticky honeydew residue, curled or distorted new growth.
• What causes it: Rapidly reproducing sap-sucking insects that thrive in warm weather. Ants may farm them.
• How to fix/prevent it: Strong water spray to knock them off. Encourage ladybugs and lacewings. Use insecticidal soap or neem oil. Avoid excess nitrogen fertilizer.

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: Cabbage looper moths laying eggs on the plants.
• How to fix/prevent it: Similar to cabbage worms: Bt spray, handpicking, row covers, and attracting beneficial insects.

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: An oomycete pathogen that spreads in cool, humid conditions via wind-carried spores.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation. Water at the base. Use copper-based fungicides for prevention.

Southern California Specific Challenges: Our hot, dry summers can stress collard greens, making them more susceptible to pests and diseases. Ensure consistent watering, especially during heat waves, and provide some afternoon shade in inland areas. Santa Ana winds can also quickly dry out plants, so monitor soil moisture closely during these events.

Companion planting can significantly benefit your collard greens in Southern California.

Good companions include onions and garlic, which deter pests like aphids and cabbage worms. Beets improve soil health and provide nutrients, while potatoes offer ground cover that helps retain moisture. Dill attracts beneficial insects like ladybugs and lacewings, which prey on aphids and other pests.

Avoid planting collard greens near strawberries or tomatoes. Strawberries compete for nutrients, and tomatoes can attract pests that also affect collards.