Bok Choy in Zone 7A — Midwest

Bok choy is a fantastic addition to any Midwest garden. It's quick to mature, delivering tasty, nutritious leaves for stir-fries, soups, and salads. The plant thrives during our spring and fall, offering a delicious alternative when the summer heat makes growing other greens a challenge.

The Midwest weather can be unpredictable. We're known for variable springs and summer heat spells. Don't worry! With a little planning and attention to timing, you can easily enjoy a bountiful bok choy harvest during our 193-day growing season.

Starting bok choy indoors isn't always necessary, but it can give you a head start, especially if you're eager for an early spring harvest. Begin indoors in early to late March, about four weeks before you plan to transplant. This is a good idea if you want to get the plants in the ground as soon as the soil is workable.

Use seed trays or small pots filled with a good seed-starting mix. Keep the soil consistently moist, and consider bottom watering to prevent damping-off. Place the trays under grow lights or in a very sunny window. Remember, our Midwest springs can be moderate-to-late, so indoor starting offers some climate control.

Transplant your bok choy seedlings outdoors from early April through late May. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Space the plants 6-10 inches apart in well-drained soil. Keep an eye on the forecast. Those early spring days can still bring unexpected cold snaps. Be ready to cover the seedlings if a late frost threatens.

Direct sowing is a straightforward way to grow bok choy in the Midwest. Sow seeds directly into the garden from late March through late August. This gives you a long window for multiple harvests.

Prepare the soil by loosening it and adding compost. Bok choy prefers soil temperatures between 50°F and 70°F for optimal germination. Plant seeds about ¼ inch deep and space them 6-10 inches apart. Thin seedlings as needed. Direct sowing is convenient, but be aware that young seedlings are more vulnerable to pests.

Bok choy needs consistent moisture to thrive, especially during our Midwest summers. Aim to keep the soil evenly moist, but not waterlogged. Bok choy that dries out is likely to bolt, so stay vigilant.

During the spring and fall, when temperatures are milder, water deeply once or twice a week, providing about 1 inch of water each time. In the summer, increase watering to every other day, or even daily during heat spells, ensuring the top 2 inches of soil stay moist. Use the finger test to check: if the soil feels dry 2 inches down, it's time to water.

Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our moderate-to-humid climate. Signs of underwatering include wilting leaves, while yellowing leaves can indicate overwatering. A layer of mulch, like straw or shredded leaves, can help retain soil moisture and regulate soil temperature.

You can expect your first bok choy harvest from mid-May through late October. Bok choy matures quickly, usually within 45 days. You can harvest baby bok choy when the leaves are 6-8 inches tall or wait until the plant reaches its full size of 12-15 inches.

To harvest, cut the entire plant off just above the base. This allows the plant to potentially regrow for a second harvest. Alternatively, you can harvest individual outer leaves as needed, encouraging continued production.

As mid- October approaches, keep an eye on the forecast. Bok choy can tolerate a light frost, but a hard freeze will damage the leaves. If a freeze is predicted, harvest any remaining mature plants.

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

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves, especially on young seedlings. You might see small, dark beetles jumping when disturbed.
• What causes it: These small jumping beetles feed on the leaves, and the damage is most severe on young, vulnerable plants.
• How to fix/prevent it: Use row covers to protect seedlings. Delay planting until plants are larger and more resilient. You can also try coating the leaves with kaolin clay or spraying with neem oil. Interplanting with basil or catnip may help deter them.

Cabbage Worms

• What it looks like: Smooth green caterpillars chewing irregular holes in the leaves. You might also see dark green droppings and white cabbage butterflies fluttering around your plants.
• What causes it: These caterpillars are the larvae of cabbage butterflies. They can go through multiple generations during our warm growing season.
• How to fix/prevent it: Bt (Bacillus thuringiensis) spray is very effective. Use floating row covers to prevent butterflies from laying eggs. Handpick caterpillars when you see them. Interplant with aromatic herbs like thyme or sage to deter the butterflies.

Slugs

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

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: Bok choy is a cool-season crop, and it bolts when exposed to extended warm temperatures. This is common during our summer heat spells.
• How to fix/prevent it: Time your plantings for cooler weather in spring and fall. Choose bolt-resistant varieties. Provide shade during warm spells with shade cloth. Mulch to keep the soil cool. Harvest your bok choy before bolting progresses too far.

Midwest Specific Challenges: Our moderate-to-hot summers and moderate-to-humid conditions mean you need to be extra vigilant about watering and pest control. Flea beetles and cabbage worms thrive in warm weather, and the humidity can encourage slugs and fungal diseases. Pay close attention to your plants and take action quickly to address any problems.

Good companions for bok choy include garlic and onions. These alliums help deter pests like aphids and cabbage worms with their strong scent. Beets also make good neighbors, as they don't compete for the same nutrients and can help loosen the soil. Lettuce and spinach are compatible because they have similar growing requirements and don't crowd each other.

Avoid planting bok choy near strawberries or tomatoes. Strawberries are susceptible to some of the same pests, which can spread to the bok choy. Tomatoes can also stunt the growth of bok choy, as they require different soil conditions and nutrients.