Cabbage in Zone 7A — Pacific Northwest

Cabbage is a rewarding crop to grow here in the Pacific Northwest. The cool nights really bring out its sweetness, and there's nothing like fresh, crisp coleslaw made with cabbage you grew yourself. Plus, it's incredibly versatile in the kitchen, from slaws to stir-fries to fermented dishes.

We do face some unique challenges in our region, like cool spring soil and the risk of late blight. But with careful timing and a few preventative measures, you can absolutely enjoy a bountiful cabbage harvest within our 183-day growing season.

To get a head start on your spring cabbage crop, start seeds indoors from mid-February through early March. This gives your plants about 6 weeks to develop before transplanting. Use seed trays filled with a good quality seed starting mix, and provide consistent warmth, around 70°F, to encourage germination.

Consistent moisture is key. I like to bottom water my seed trays to prevent damping off and ensure the seedlings get a good, even soak. Place the tray in a shallow container of water for about 15-20 minutes until the surface of the soil is moist. Remember, spring can be slow to warm up here, so indoor starting really gives you a leg up.

You can transplant your cabbage seedlings outdoors from early April through early May. Be sure to harden them off first by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight we often get during that time.

Space the seedlings 12-18 inches apart to give them enough room to mature. Keep an eye on the forecast; a late cold snap isn't uncommon, so be ready to cover your young plants if needed.

Cabbage needs consistent moisture to thrive, but overwatering can lead to problems, especially with our wet springs. Aim for about 1 inch of water per week, but adjust based on rainfall. During the dry summer months, you'll likely need to water more frequently.

The finger test is a good way to check soil moisture. Stick your finger about 2 inches into the soil near the base of the plant. If it feels dry, it's time to water. Water at the base of the plant to avoid wetting the leaves, which can encourage fungal diseases in our sometimes humid conditions.

Signs of underwatering include wilting leaves and slow growth. Overwatering can cause yellowing leaves and potentially root rot. A layer of mulch, like straw or compost, can help retain moisture and suppress weeds, reducing the need for frequent watering.

Your first cabbage harvest should be ready from mid-June through early August, about 70 days after transplanting. The best way to tell if a cabbage is ready is to give the head a gentle squeeze. It should feel firm and solid, not soft or loose.

Also, make sure the head has reached a good size for the variety you're growing. To harvest, simply cut the cabbage head at the base with a sharp knife.

As we approach mid-October and the first frost, harvest any remaining mature heads. Even though cabbage is frost-tolerant, a hard freeze can damage the outer leaves.

Here are some common issues you might encounter with cabbage in the PNW:

• 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. They can have multiple generations in our mild summers.
• How to fix/prevent it: Bt spray is very effective, especially when the caterpillars are small. Floating row covers prevent the butterflies from laying eggs. Handpick caterpillars when you see them. Interplant with aromatic herbs like thyme and sage to deter the butterflies and attract beneficial insects like 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 behind the veins.
• What causes it: Similar to cabbage worms, these are the larvae of a moth. They thrive in our mild summers.
• How to fix/prevent it: Bt spray works well on loopers, too. Handpicking is also effective. Encourage natural predators like birds and lacewings.
• Splitting
• What it looks like: The cabbage head cracks open.
• What causes it: Inconsistent watering. A period of drought followed by heavy watering causes the head to grow too quickly and split.
• How to fix/prevent it: Consistent watering is key. Mulch around the plants to help retain moisture. If heavy rain is expected after a dry spell, consider harvesting mature heads early.
• 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, common in our region.
• 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 summers and dry-summer rainfall can create ideal conditions for pests like cabbage worms and loopers. Late blight, while more common on tomatoes and potatoes, can occasionally affect cabbage, so good air circulation is important. Cool spring soil can slow growth, making indoor starting essential.

Companion planting can really help your cabbage thrive. Green beans are great companions because they fix nitrogen in the soil, which cabbage loves. Celery is said to deter cabbage white butterflies. Onions also deter pests. Potatoes don't directly benefit the cabbage, but they don't compete for the same nutrients and can be grown nearby. Dill attracts beneficial insects that prey on cabbage pests.

Avoid planting cabbage near tomatoes, strawberries, or peppers. Tomatoes and peppers are susceptible to the same diseases as cabbage, increasing the risk of spreading problems. Strawberries can compete for nutrients and space. These considerations are particularly relevant in our PNW gardens, where space can be limited and disease pressure can be high.