Mustard Greens in Zone 8B — Southern California

Mustard greens bring a zesty, peppery bite to salads, stir-fries, and braised dishes, and they're incredibly easy to grow in our Southern California climate. With our long growing season and mild winters, you can enjoy a year-round harvest of these nutritious greens right from your backyard.

While we face challenges like drought and occasional heat waves, careful timing and water-wise practices will ensure a successful mustard greens crop. Our 298-day growing season gives you plenty of opportunity to get it right, even if you're a beginner gardener.

Starting mustard greens indoors gives you a head start, especially for an early spring crop. Sow seeds indoors from early to late January, about three weeks before you plan to transplant. This helps you get a jump on the season and ensures the plants are well-established before our summer heat inland arrives.

Use seed trays or small pots filled with a good seed-starting mix. Keep the soil consistently moist by bottom watering, placing the tray in a shallow dish of water until the surface of the soil is damp. Provide warmth and plenty of light, either from a sunny windowsill or a grow light. This method is useful for those of us on the coast where spring comes very-early.

Transplant your mustard greens seedlings outdoors from early February through mid March. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind, preventing transplant shock.

Space the seedlings 6-12 inches apart in well-drained soil. Keep an eye on the weather forecast. Late cold snaps can happen, so be ready to cover the seedlings if frost threatens.

Direct sowing is a simple way to grow mustard greens in Southern California, and it works well for most of the year. Sow seeds mid January through mid October, ensuring a continuous harvest. Prepare the soil by loosening it and adding compost.

Sow seeds 1/4 inch deep and keep the soil consistently moist until they germinate. Thin the seedlings to 6-12 inches apart once they have a few true leaves. Direct sowing is especially convenient during our mild fall and winter.

Mustard greens need consistent moisture, especially in our semi-arid Southern California climate. Aim to keep the soil evenly moist, but not waterlogged. Drought stress can make the leaves spicier and trigger bolting, which you want to avoid.

During the cooler months (late fall through early spring), water deeply once or twice a week, providing about 1 inch of water each time. In the summer heat inland, you may need to water every day or every other day, especially if you're growing in containers. Use the finger test: if the top 2 inches of soil feel dry, it's time to water.

Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases, especially with our low-to-moderate humidity. Signs of underwatering include wilting leaves, while overwatering can lead to yellowing leaves and root rot. A layer of mulch, like straw or wood chips, will help retain moisture and keep the soil cool.

You can expect your first harvest of mustard greens about 45 days after planting, usually from early March through mid December in our region. Harvest young leaves for a milder flavor, or wait for larger leaves if you prefer a spicier kick. Pick the leaves before the plant starts to flower (bolt).

To harvest, simply snip off the outer leaves with scissors or a knife, leaving the inner leaves to continue growing. This encourages continuous production throughout the season. As our first frost approaches in early December, harvest any remaining leaves to enjoy before the cold weather sets in.

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

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves, especially on young seedlings. You might see small dark beetles that jump when disturbed.
• What causes it: Small jumping beetles that feed on leaves. They're most damaging to small, young plants. Our warm springs and summers can lead to rapid flea beetle reproduction.
• How to fix/prevent it: Use row covers to protect seedlings. Delay planting until plants are larger and more resilient. Spray with kaolin clay or neem oil. Interplant with basil or catnip.

Aphids

• What it looks like: Clusters of tiny soft-bodied insects (green, black, or white) on stems and leaf undersides. Sticky honeydew residue and curled or distorted new growth.
• What causes it: Rapid-reproducing sap-sucking insects. Populations explode in warm weather. Ant colonies may farm them for honeydew.
• How to fix/prevent it: Spray aphids off with a strong stream of water. Encourage ladybugs and lacewings (natural predators). Use insecticidal soap for heavy infestations. Avoid excess nitrogen fertilizer.

Cabbage Worms

• What it looks like: Smooth green caterpillars on leaves, irregular holes chewed in leaves, and dark green droppings. You might see white butterflies hovering around your plants.
• What causes it: Larvae of white cabbage butterflies. We often have multiple generations per season in our warm climate.
• How to fix/prevent it: Bt spray is very effective. Use floating row covers to prevent egg laying. Handpick caterpillars. Interplant with aromatic herbs like thyme and sage.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk, and the leaves become tough and bitter.
• What causes it: Extended warm temperatures. Mustard greens bolt when days consistently exceed 80°F. This is a common issue during our summer heat inland.
• How to fix/prevent it: Time plantings for cool weather (spring or fall). Choose bolt-resistant varieties. Provide shade during warm spells. Mulch to keep the soil cool. Harvest before bolting progresses.

Southern California Specific Challenges: Our hot, dry summers and occasional Santa Ana winds can stress mustard greens, making them more susceptible to bolting and pests. Consistent watering is key, and providing shade during the hottest part of the day can help prevent bolting.

Mustard greens thrive alongside certain companion plants in Southern California gardens. Onions and garlic help deter pests like aphids and flea beetles. Beets are good companions because they don't compete for the same nutrients. Dill attracts beneficial insects that prey on pests. Lettuce provides ground cover, helping to keep the soil cool and moist.

Avoid planting mustard greens near strawberries or tomatoes. Strawberries are susceptible to verticillium wilt, which can also affect mustard greens. Tomatoes can attract aphids and other pests that will then move on to your mustard greens.