Bok Choy in Zone 6B — Pacific Northwest

Bok choy is a fantastic addition to any Pacific Northwest garden. Its mild flavor and crisp texture make it incredibly versatile in stir-fries, soups, and salads. The cool nights we get here in the summer actually enhance the flavor, making your homegrown bok choy even better than what you'll find at the store.

Growing bok choy in our region does come with a few challenges, like cool soil in the spring and the potential for bolting if we get an unexpected heat wave. But with a little planning and attention to timing, you can easily enjoy a successful harvest within our 162-day growing season.

Starting bok choy indoors is an option, especially if you want a head start on the season. Sow seeds indoors from late March through mid April, about four weeks before you plan to transplant them outside. Use seed trays filled with a good seed-starting mix.

Keep the trays in a warm location, ideally around 70°F, and provide plenty of light, either from a sunny windowsill or a grow light. Bottom watering helps prevent damping-off, which can be a problem with our overcast spring days. While starting indoors is possible, direct sowing often works just as well here, given our mild summers.

Transplant your bok choy seedlings outdoors from early May through mid June, after the danger of hard frost has passed. Before transplanting, harden off the seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight.

Space the plants 6-10 inches apart in well-drained soil. Keep an eye on the weather forecast – a late cold snap can still happen in early May, so be prepared to cover your transplants if needed.

Direct sowing bok choy is a simple and effective method in the Pacific Northwest. Sow seeds from mid April through mid August for a continuous harvest. Prepare the soil by loosening it and adding compost to improve drainage and fertility.

Sow seeds about ½ inch deep and 6-10 inches apart. Keep the soil consistently moist, especially during germination. One potential downside to direct sowing is that young seedlings are more vulnerable to slugs, so be prepared to take preventative measures.

Bok choy needs consistent moisture to thrive, especially during our dry summer months. Aim to keep the soil evenly moist, but not waterlogged. A good rule of thumb is to check the soil moisture about 2 inches down – if it feels dry, it's time to water.

During the spring and fall, when we get more natural rainfall, you may only need to water once or twice a week, providing about 1 inch of water each time. In the drier summer months, increase watering to 2-3 times per week. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our region.

Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to yellowing leaves and root rot. Applying a layer of mulch around your bok choy plants helps retain moisture and suppress weeds, which is especially helpful during our drier periods.

You can expect your first bok choy harvest from early June through mid October, depending on when you planted. Baby bok choy can be harvested when the leaves are 6-8 inches tall, while full-sized bok choy is ready when it reaches 12-15 inches. Look for firm, crisp leaves with vibrant color.

To harvest, cut the entire plant off at the base, just above the soil line. For continued production, you can also harvest individual outer leaves, allowing the plant to continue growing. As the first frost approaches in early October, harvest any remaining bok choy, even if it's not fully mature, to prevent frost damage.

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

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.
• How to fix/prevent it: Row covers protect seedlings. Delay planting until plants are larger. Kaolin clay coating can deter them. Neem oil spray can help. Interplant with basil or catnip. Healthy plants outgrow damage.

Cabbage Worms

• What it looks like: Smooth green caterpillars on brassica leaves. Irregular holes chewed in leaves. Dark green droppings. You might see white butterflies hovering around your plants.
• What causes it: These are the larvae of white cabbage butterflies.
• How to fix/prevent it: Bt spray is effective. Floating row covers prevent egg laying. Handpick caterpillars. Interplant with aromatic herbs like thyme and sage. Encourage parasitic wasps.

Slugs

• What it looks like: Irregular holes in leaves, especially low-growing plants. Silvery slime trails on leaves and soil. Damage is worse at night and in wet weather.
• What causes it: These gastropods feed at night in moist conditions. They hide under mulch, boards, and debris during the day. Our wet springs and mild, damp weather create ideal conditions for slugs.
• How to fix/prevent it: Beer traps (shallow dish of beer sunk into soil). Iron phosphate bait (pet-safe). Remove hiding spots. Water in morning so soil surface dries by evening. Copper tape around beds. Diatomaceous earth around plants.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk when temperatures rise. Leaves become tough and bitter. Harvest quality declines.
• What causes it: Bok choy is a cool-season crop and bolts when temperatures are consistently above its comfort zone.
• How to fix/prevent it: Time plantings for cool weather (spring/fall). Choose bolt-resistant varieties. Provide shade during warm spells. Mulch to keep soil cool. Harvest before bolting progresses too far.

Pacific Northwest Specific Challenges: Our mild summers can be a blessing, but unexpected heat waves can still cause bolting. Slug pressure is also a significant concern, especially during our wet springs. Late blight isn't a direct threat to bok choy, but it's a regional concern for other crops like tomatoes and potatoes, so maintaining good garden hygiene is always a good idea.

Companion planting can help your bok choy thrive in the Pacific Northwest. Garlic and onions are excellent companions because their strong scent deters pests like flea beetles and cabbage moths. Beets are also good companions, as they don't compete for the same nutrients and can help improve soil structure.

Lettuce and spinach make good ground cover around bok choy, helping to retain moisture and suppress weeds. Avoid planting bok choy near strawberries or tomatoes. Strawberries can attract slugs, which will then target your bok choy. Tomatoes are heavy feeders and can compete with bok choy for nutrients.