Cabbage in Zone 8A — Pacific Northwest

Growing cabbage here in the Pacific Northwest is incredibly rewarding. There's nothing like the crisp, fresh flavor of a homegrown cabbage, especially when our cool nights concentrate the sugars. Cabbage is versatile in the kitchen, from slaws to stir-fries, and there's a real satisfaction in harvesting those dense heads you nurtured from tiny seedlings.

While we enjoy mild summers, our wet springs and the risk of late blight can be a challenge for cabbage. But with a little planning and the advantage of our 203-day growing season, you can easily time your planting for a successful harvest.

To get a jump start on your cabbage crop, start seeds indoors from early to late February. This gives the seedlings plenty of time to develop before transplanting. Use seed trays or small pots filled with a good seed-starting mix.

Keep the trays warm (around 70°F) and provide plenty of light, either with a grow light or a sunny windowsill. Bottom watering will help prevent damping-off, which can be a problem with our overcast spring days. Just set the tray in a shallow dish of water and let the soil soak it up from the bottom.

Remember that spring starts slow here, so be patient! Cabbage needs consistent moisture and light to thrive indoors before the weather warms up enough to move them outside.

Transplant your cabbage seedlings outdoors from late March through late April. Before planting, be sure to harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight.

Space your cabbage plants 12-18 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast, as we can still get some chilly snaps during this time. Protect your young plants with row covers if frost threatens.

Cabbage needs consistent moisture to thrive, but overwatering can be just as harmful. The key here in the PNW is to find the right balance, considering our dry-summer climate.

During our wet springs, you may not need to water much at all, but once the dry summer months arrive, you'll need to water regularly. Use the "finger test" – if the top 2 inches of soil feel dry, it's time to water. Aim for about 1 inch of water per week, delivered at the base of the plant to avoid wetting the leaves and encouraging fungal diseases.

Signs of underwatering include wilting leaves, while yellowing leaves can indicate overwatering. A layer of mulch around your cabbage plants will help retain moisture and keep the soil cool, which is especially important during our mild summers.

You can expect to harvest your cabbage from early June through late July, about 70 days after transplanting. The best way to tell if a cabbage is ready to harvest is to give the head a gentle squeeze. It should feel firm and solid.

Also, check that it has reached its full size for the variety you're growing. To harvest, simply cut the cabbage head at the base with a sharp knife.

As we approach our first frost in late October, harvest any remaining cabbage heads, even if they aren't quite fully mature. They'll store well in a cool, dry place.

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 during our long growing season.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent egg laying. Handpick caterpillars. Interplant with aromatic herbs (thyme, 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 behind.
• What causes it: Cabbage looper moths lay their eggs on the underside of leaves. The larvae hatch and begin feeding.
• How to fix/prevent it: Similar to cabbage worms, Bt spray is effective. Handpick loopers. Encourage beneficial insects like lacewings and parasitic wasps.

Splitting

• What it looks like: The cabbage head cracks or splits open.
• What causes it: Inconsistent watering. Heavy watering after a dry spell causes the head to swell too quickly, leading to splitting.
• How to fix/prevent it: Maintain consistent soil moisture. Water regularly during dry periods. Harvest heads as soon as they are mature to prevent over-ripening and 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, which we often have in the spring.
• 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 heat and dry-summer rainfall can contribute to splitting if watering isn't consistent. Also, our wet springs can make cabbage more susceptible to clubroot. Keep an eye out for slugs, which love young cabbage plants.

Companion planting can really help your cabbage thrive here. Green beans fix nitrogen in the soil, which cabbage loves. Celery is thought to deter cabbage white butterflies. Onions and dill are also good choices, as their strong scents can confuse pests. Potatoes are said to improve cabbage growth.

Avoid planting cabbage near tomatoes, strawberries, and peppers. Tomatoes and strawberries can stunt the growth of cabbage, and peppers compete for the same nutrients in the soil.