Collard Greens in Zone 10A — Southern California

Collard greens are a Southern staple that thrive surprisingly well in our Southern California climate. You get that slightly bitter, earthy flavor that's fantastic braised, sauteed, or even added raw to salads for a bit of a kick. Plus, a steady supply of fresh greens right from your backyard is especially satisfying in our year-round growing environment.

We definitely have our challenges here – drought, the occasional Santa Ana winds, and summer heat inland. But with some smart timing, these greens can give you a year-round harvest. Our long growing season (349 days!) gives you plenty of opportunities to get it right.

Starting collard greens indoors isn’t strictly necessary in our mild climate, but it can give you a head start, especially for a late winter/early spring harvest. If you want to go this route, start your seeds indoors from mid December through early January, about four weeks before you plan to transplant.

Use seed trays with a good seed-starting mix. Keep them consistently moist (bottom watering helps prevent damping off) and warm, and provide plenty of light – a simple shop light works wonders. Given our very-early spring character, this can help you jump-start your garden.

Transplant your collard greens outdoors from mid January through mid February. Before you plant, be sure to harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Space the plants 18-24 inches apart to give them room to grow. Even though this is typically our rainy season, watch for unexpected dry spells and protect seedlings from any late cold snaps.

Direct sowing is a great option for collard greens here in SoCal. You can sow seeds directly into the garden from early January through early October.

Make sure the soil is well-worked and the soil temperature is consistently above 50°F. Plant seeds about ½ inch deep, and thin seedlings to 18-24 inches apart once they emerge. Direct sowing is less work, but seedlings are more vulnerable to pests and weather fluctuations.

Collard greens need consistent moisture to produce tender, flavorful leaves. While they're more heat-tolerant than some other brassicas, they definitely aren't drought-tolerant and suffer without regular watering, especially with our summer heat inland.

During the cooler, winter-wet months, you might only need to supplement rainfall every week or two, giving them about 1 inch of water per week if it doesn't rain. In the hotter, drier months, especially inland, increase that to 2 inches per week, and check the soil moisture regularly. Stick your finger about 2 inches deep – if it feels 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. Wilting leaves are a sign of underwatering, while yellowing leaves can indicate overwatering. A layer of mulch around the base of the plants will help retain moisture and keep the soil cool, which is especially important during those hot summer months.

You can expect your first harvest of collard greens starting around mid March and continuing through early January. The leaves are ready to harvest when they're about 10-12 inches long.

Harvest the lower, outer leaves first, leaving the top rosette intact. This allows the plant to continue producing new leaves throughout the season. The flavor of collard greens actually sweetens after a light frost, so don't be afraid to leave them in the garden as late as possible. As our first frost approaches in late December, harvest any remaining large leaves to enjoy.

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

Cabbage Worms

• What it looks like: You'll see smooth, green caterpillars munching on leaves, leaving irregular holes and dark green droppings behind. White butterflies fluttering around your plants are a warning sign.
• What causes it: These are the larvae of those white cabbage butterflies. They can go through multiple generations in our long, warm growing season.
• How to fix/prevent it: Bt spray is very effective. Floating row covers will prevent the butterflies from laying eggs. You can also handpick the caterpillars. Interplanting with aromatic herbs like thyme and sage can help deter them, and encouraging parasitic wasps can provide natural control.

Aphids

• What it looks like: Clusters of tiny, soft-bodied insects (green, black, or white) congregate on stems and the undersides of leaves. You might also notice sticky honeydew residue and curled or distorted new growth.
• What causes it: Aphids are sap-sucking insects that reproduce rapidly, especially in warm weather. Ant colonies often "farm" them for their honeydew.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage ladybugs and lacewings, which are natural predators. Insecticidal soap can be used for heavy infestations, and neem oil works systemically. Avoid over-fertilizing with nitrogen, as this attracts aphids.

Cabbage Loopers

• What it looks like: Similar to cabbage worms, but these caterpillars move in a looping motion. They also chew holes in leaves, sometimes leaving only the veins.
• What causes it: Cabbage loopers are another type of caterpillar that thrives in warm weather.
• How to fix/prevent it: Similar controls as for cabbage worms: Bt spray, handpicking, floating row covers, and attracting beneficial insects.

Downy Mildew

• What it looks like: You'll see yellow patches on the tops of leaves with fuzzy, gray-purple growth on the undersides. Leaves will eventually brown and die, starting from the bottom of the plant.
• What causes it: This is caused by 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 around your plants. Water at the base, avoiding overhead watering. Copper-based fungicides can be used for prevention.

Southern California Specific Challenges: Our hot summers inland can stress collard greens, making them more susceptible to pests and diseases. Consistent watering is key, especially during Santa Ana winds, which can quickly dry out the soil. During fire season, be extra vigilant about removing any dry or dead leaves to reduce fire risk.

Companion planting can really boost your collard green crop. Onions and garlic are great companions because their strong scent deters many pests. Beets and potatoes are also good choices, as they don't compete for the same nutrients in the soil. Dill attracts beneficial insects that prey on aphids and cabbage worms.

Avoid planting strawberries or tomatoes near your collard greens. Strawberries can attract slugs and snails, which can also damage your greens, and tomatoes are susceptible to diseases that can spread to collards.