Bok Choy in Zone 3B — Midwest

Bok choy is a great addition to a Midwest garden. It's quick to mature, so you can get multiple harvests even with our shorter growing season. Plus, it's incredibly versatile in the kitchen – stir-fries, soups, salads, you name it. There's nothing quite like the satisfaction of harvesting your own fresh greens!

The Midwest weather can be unpredictable, with variable springs and summer heat spells. But with careful timing, you can absolutely grow bok choy successfully during our 118-day growing season. A little planning goes a long way.

Starting bok choy indoors in the Midwest is an option, but not always necessary. Given our moderate-to-late spring, it can be helpful to get a jump start. If you want to start seeds indoors, do so from mid-April through early May, about four weeks before you plan to transplant them.

Use seed trays and a good seed-starting mix. Keep the soil consistently moist, and provide warmth and plenty of light. Bottom watering is a good method to prevent damping off. This gives you a head start, especially if we have a late frost.

Transplanting bok choy outdoors in the Midwest should happen from mid-May through early July. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

When transplanting, space the plants 6-10 inches apart. Keep an eye on the weather forecast. Our springs can be variable, and a late frost can still happen. Be prepared to cover your transplants if necessary.

Direct sowing bok choy is a perfectly viable option in the Midwest, and it's often the easiest method. Sow seeds directly into the garden from early May through mid-July. The fertile soil warms up quickly enough for good germination.

Make sure the soil is well-prepared and consistently moist. Thin seedlings to 6-10 inches apart once they emerge. Direct sowing is a great way to get a continuous harvest throughout the summer.

Bok choy needs consistent moisture, especially in the Midwest, where we can experience summer heat spells. Aim to keep the soil evenly moist, but not waterlogged. The "finger test" is a good way to check: if the top two inches of soil feel dry, it's time to water.

During the hotter parts of summer, your bok choy might need up to an inch of water per week, either from rainfall or irrigation. Water at the base of the plants to avoid wetting the leaves, especially with our moderate-to-humid summers. Wet leaves can encourage fungal diseases.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to yellowing leaves and root rot. A layer of mulch can help retain moisture and keep the soil cool, which is especially helpful during our hotter summer months.

You can expect your first harvest of bok choy from mid-June through late September in the Midwest. 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 until it reaches full size at 12-15 inches.

To harvest, cut the plant above the base, leaving the roots intact. This allows the plant to regrow and produce more leaves. Continue harvesting leaves as needed throughout the season.

As our first frost approaches in mid-September, harvest any remaining bok choy. It is semi-hardy, but a hard frost will damage it. You can succession plant to extend your harvest.

Here are some common problems you might encounter with bok choy in the Midwest:

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves. You'll see small dark beetles that jump when disturbed. The worst damage happens to young seedlings.
• What causes it: Small jumping beetles that feed on the leaves. They are most damaging to small, young plants.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. Delay planting until plants are larger. A kaolin clay coating can help. Neem oil spray is also effective. 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 and dark green droppings. White butterflies fluttering around your plants are a sign.
• What causes it: The larvae of those white cabbage butterflies. They can go through multiple generations per season if it stays warm long enough.
• How to fix/prevent it: Bt spray is very effective. Floating row covers will prevent the butterflies from laying eggs. Handpick the caterpillars when you see them. Interplant with aromatic herbs like thyme or sage. Encourage parasitic wasps.

Slugs

• What it looks like: Irregular holes in the leaves, especially on the lower parts of the plant. You'll see silvery slime trails on the leaves and soil. Damage is usually 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.
• How to fix/prevent it: Beer traps work well. Place a shallow dish of beer sunk into the soil. Iron phosphate bait is pet-safe. Remove any hiding spots. Water in the morning so the soil surface dries out by evening. Copper tape around the beds can deter them. Diatomaceous earth around the plants also helps.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk. The leaves become tough and bitter, and the harvest quality declines.
• What causes it: Extended warm temperatures cause this cool-season crop to bolt. Bok choy bolts when the days are consistently above 80°F.
• How to fix/prevent it: Time your plantings for cooler weather in the spring or fall. Choose bolt-resistant varieties. Provide shade during warm spells. Mulch to keep the soil cool. Harvest before bolting progresses too far.

Midwest Specific Challenges: The moderate-to-hot heat and moderate-to-humid summers can stress bok choy, making it more susceptible to bolting and pests. Our wet-summer rainfall patterns mean you'll need to monitor soil moisture carefully to avoid overwatering.

Good companion plants for bok choy in the Midwest include garlic and onions. Their strong scent can help deter pests like flea beetles and cabbage worms. Beets are also good companions, as they don't compete for the same nutrients and can help improve the soil structure. Lettuce and spinach can provide ground cover, helping to retain moisture and suppress weeds.

Avoid planting bok choy near strawberries or tomatoes. Strawberries can attract slugs, which will also feed on the bok choy. Tomatoes can compete for nutrients and attract pests that also affect bok choy.