Cabbage in Zone 6A — Pacific Northwest

Cabbage is a rewarding crop for the Pacific Northwest garden, offering crisp, flavorful heads perfect for slaws, ferments, or hearty braises. The cool nights and mild summers of our region really bring out the sweetness in cabbage, making it far superior to anything you'll find at the grocery store. Plus, there's something deeply satisfying about harvesting a hefty cabbage head you nurtured from a tiny seed.

Our wet springs and relatively short growing season (around 148 days) can present challenges, but with careful timing, you can absolutely grow beautiful, delicious cabbage here in Zone 6A. Starting seeds indoors gives you a head start, ensuring a spring harvest before the first frosts arrive.

To get a jump on the season, start your cabbage seeds indoors from early to late March. This gives them about 6 weeks to get established before transplanting. Use seed trays or small pots filled with a good seed-starting mix.

Keep the soil consistently moist – bottom watering is a great way to prevent damping off. Provide warmth with a heat mat and plenty of light with grow lights, especially during our often overcast spring days.

Remember, spring in the PNW can be slow to warm up, so these indoor conditions are vital for strong seedling development.

Transplant your cabbage seedlings outdoors from late April through late May, after the danger of hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. Start with an hour or two of sheltered sunlight and increase the duration each day.

Plant your cabbage seedlings 12-18 inches apart in well-drained soil. The spacing allows them to develop without crowding. Be sure to protect young transplants from slugs, which are prevalent in our wet springs.

Cabbage needs consistent moisture to thrive, but overwatering can be just as detrimental. Aim to keep the soil evenly moist, but not soggy. During our dry summer months, check the soil moisture regularly.

Stick your finger about 2 inches deep into the soil – if it feels dry, it's time to water. Typically, cabbage needs about 1-1.5 inches of water per week, either from rainfall or irrigation. Water at the base of the plant to avoid wetting the leaves, reducing the risk of fungal diseases in our climate.

Signs of underwatering include wilting or stunted growth. Overwatering can lead to yellowing leaves and root rot. A layer of mulch, like straw or shredded leaves, can help retain moisture and suppress weeds.

Your first cabbage harvest should be ready from early July through late August, depending on the variety and when you transplanted. Cabbage is ready to harvest when the head feels firm and solid when squeezed. It should also be close to the full size expected for that particular variety.

To harvest, use a sharp knife to cut the head at the base of the plant. Leaving the roots intact can sometimes encourage the plant to produce smaller side shoots.

As we approach our first frost in early October, harvest any remaining mature heads. Smaller, less mature heads can be used for slaw or quick pickles.

Here are some common problems you might encounter growing cabbage in the Pacific Northwest:

Cabbage Worms

• What it looks like: Smooth green caterpillars on brassica leaves. Irregular holes chewed in leaves. Dark green droppings. White butterflies hovering around plants.
• What causes it: Larvae of white cabbage butterflies. Multiple generations can occur if our mild summers are long enough.
• How to fix/prevent it: Bt spray is very effective. Floating row covers, installed right after transplanting, prevent egg laying. Handpick caterpillars when you see them. Interplant with aromatic herbs like thyme and sage. Encourage parasitic wasps.

Cabbage Loopers

• What it looks like: Pale green caterpillars that move in a looping motion. They chew large holes in leaves, often leaving only the veins.
• What causes it: Similar to cabbage worms, these are the larvae of moths that lay eggs on the plants.
• How to fix/prevent it: Bt spray is also effective against cabbage loopers. Handpicking can help control small infestations. Row covers can prevent moths from laying eggs.

Splitting

• What it looks like: The cabbage head cracks open.
• What causes it: Inconsistent watering, especially heavy watering after a period of drought. Rapid growth spurts from temperature swings can also cause it.
• How to fix/prevent it: Maintain consistent soil moisture. Water deeply and regularly during dry spells. Harvest cabbage heads as soon as they are mature to prevent them from splitting.

Clubroot

• What it looks like: Stunted growth, wilting in afternoon heat, yellowing leaves. Roots are swollen, distorted, and club-shaped when dug up.
• What causes it: Soil-borne pathogen (Plasmodiophora brassicae) that persists in soil for 10+ years. Favors acidic, wet soil.
• How to fix/prevent it: Raise soil pH to 7.0-7.2 with lime. Improve drainage. Rotate brassicas on a 7-year cycle. Remove and destroy infected plants (don't compost). Start transplants in sterile mix.

Pacific Northwest Specific Challenges: Our mild, dry summers generally mean fewer pest pressures than other regions, but slugs are a constant concern, especially for young transplants. Consistent moisture management is key to preventing splitting, and choosing early maturing varieties helps ensure a harvest before our wet fall weather sets in. Late blight isn't usually a major issue for cabbage itself, but be mindful of its presence in your garden if you also grow tomatoes or potatoes nearby.

Companion planting can help your cabbage thrive. Green beans add nitrogen to the soil, benefiting cabbage growth. Celery can deter cabbage white butterflies. Onions and dill repel certain pests, keeping your cabbage safe. Potatoes don't directly benefit cabbage, but they don't compete for nutrients and can be grown nearby.

Avoid planting cabbage near tomatoes, strawberries, or peppers. Tomatoes and strawberries can attract similar pests and diseases. Peppers are heavy feeders and compete for the same nutrients.