Bok Choy in Zone 8A — Pacific Northwest

Bok choy is a fantastic addition to any Pacific Northwest garden. Its mild flavor is delicious in stir-fries, soups, and salads, and its crisp texture holds up well in our cool nights. Plus, it's incredibly satisfying to harvest fresh greens right from your backyard, especially when our dry summer months might make other crops a bit more demanding.

While the PNW's wet springs and relatively short stretches of truly warm weather can present challenges, bok choy thrives with proper timing. Our long growing season—roughly 203 days—allows for multiple plantings, ensuring a steady supply of this nutritious green.

Starting bok choy indoors in the Pacific Northwest is an option, especially if you're eager for an early harvest, but it's not always necessary. Because Bok Choy is so quick to mature, direct sowing often works just as well. If you choose to start indoors, do so from early to late March, about four weeks before you intend to transplant.

Use seed trays or small pots filled with seed-starting mix. Keep the soil consistently moist by bottom watering – set the tray in a shallow dish of water until the surface looks damp. Provide warmth and plenty of light, especially given our overcast spring days. Remember, our spring start is often slow, so be patient.

Transplant your bok choy seedlings outdoors from early April through late May, once they have a few sets of true leaves. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This is essential to prevent shock.

Space plants 6-10 inches apart in well-drained soil. Keep an eye on the weather, especially for late-season frosts, which can still occur in early April here. Be sure to protect your tender seedlings if a cold snap is in the forecast.

Direct sowing bok choy is a simple and effective method for PNW gardeners. Sow seeds late March through early September for a continuous harvest. Direct sowing works well because our mild summers don't get too hot, and the cool nights improve the flavor.

Prepare the soil by loosening it and adding compost. Sow seeds about ¼ inch deep, spacing them 6-10 inches apart. Keep the soil consistently moist, especially during germination. Thin seedlings as needed to ensure proper spacing.

Consistent moisture is key to growing healthy bok choy in the Pacific Northwest. Our dry-summer climate means you'll need to pay close attention to watering, even with our mild summers. Bok choy that dries out is likely to bolt, and no one wants that.

During our wet springs, you might not need to water much at all, but once the dry summer months arrive, check the soil moisture regularly. Use the "finger test": stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Aim for about 1 inch of water per week, depending on rainfall.

Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our sometimes humid conditions. A layer of mulch, such as straw or wood chips, will help retain moisture and keep the soil cool, which is especially important during warmer spells. If the leaves are wilting, you're likely underwatering. Yellowing leaves may indicate overwatering, so adjust accordingly.

You can expect your first bok choy harvest from mid May through early November, depending on when you planted. Bok choy is ready to harvest about 45 days after planting. You can harvest baby bok choy when it's 6-8 inches tall, or wait for it to reach full size at 12-15 inches.

To harvest, cut the plant above the base, leaving the roots intact. This allows the plant to regrow, providing you with multiple harvests. Continue to water and fertilize after harvesting to encourage new growth.

As the first frost approaches in late October, harvest any remaining bok choy, even if it's not fully mature. You can use smaller leaves in salads or stir-fries.

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 also see small dark beetles that jump when disturbed.
• What causes it: These small jumping beetles feed on the leaves of brassicas. They're most damaging to small, young plants, especially in the spring.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. Delay planting until plants are larger and more resilient. Consider a kaolin clay coating or neem oil spray. Interplant with basil or catnip. Healthy, vigorous plants often outgrow the damage.

Cabbage Worms

• What it looks like: Smooth green caterpillars on your bok choy leaves. You'll see irregular holes chewed in the leaves, dark green droppings, and maybe even 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 very effective. Use floating row covers to prevent the butterflies from laying eggs on your plants. Handpick caterpillars when you see them. Interplant with aromatic herbs like thyme or sage to deter the butterflies. Encourage parasitic wasps, which prey on cabbage worms.

Slugs

• What it looks like: Irregular holes in leaves, especially on low-growing plants. Look for silvery slime trails on the leaves and soil. Damage is often worse at night and in wet weather.
• What causes it: Slugs are gastropods that feed at night in moist conditions. They hide under mulch, boards, and debris during the day. Our wet springs and mild, damp conditions make slugs a constant threat.
• How to fix/prevent it: Use beer traps (shallow dishes of beer sunk into the soil). Iron phosphate bait is also effective and pet-safe. Remove hiding spots like boards and debris. Water in the morning so the soil surface dries out by evening. Copper tape around beds can deter slugs. Diatomaceous earth around plants can also help.

Bolting in Heat

• What it looks like: The bok choy sends up a flower stalk. The leaves become tough and bitter, and the overall harvest quality declines.
• What causes it: Bok choy is a cool-season crop, and it bolts when temperatures rise.
• How to fix/prevent it: Time your plantings for cool weather in spring and fall. Choose bolt-resistant varieties. Provide shade during warm spells. Mulch to keep the soil cool. Harvest before bolting progresses too far.

Pacific Northwest Specific Challenges: Our mild summers and dry-summer rainfall can be both a blessing and a curse for bok choy. While the mild temperatures are generally favorable, extended warm spells can trigger bolting. Consistent watering is crucial to combat the dry conditions and prevent stress. Also, slugs thrive in our moist environment, so be vigilant in your slug control efforts. Late blight is usually not an issue for Bok Choy.

Good companion plants for bok choy in the Pacific Northwest include garlic and onions, which deter pests with their strong scent. Beets help by improving soil structure, while lettuce and spinach provide ground cover, suppressing weeds and keeping the soil cool.

Avoid planting bok choy near strawberries, as they can attract slugs. Tomatoes are also not ideal companions, as they prefer different soil conditions and can compete for nutrients.