Bok Choy in Zone 7B — Desert Southwest

Bok choy is a fantastic choice for Desert Southwest gardens. Its mild, slightly sweet flavor adds a delicious crunch to stir-fries, soups, and salads. Plus, growing your own means you can harvest baby bok choy for tender greens or let it mature for larger, heartier leaves. Nothing beats the satisfaction of harvesting fresh greens from your own backyard in our arid climate.

While the extreme heat of our summers can be challenging, bok choy thrives in the cooler parts of our two growing seasons. With a little planning, you can enjoy a bountiful harvest. Our long 245-day growing season gives you plenty of opportunity to get it right.

Starting bok choy indoors gives you a head start, especially for the spring season. Begin sowing seeds indoors from early February through early March, about four weeks before you plan to transplant. Use seed trays filled with a good seed-starting mix, and keep them in a warm spot with plenty of light – a sunny windowsill or under grow lights works well.

Don't forget to water from the bottom! Place the tray in a shallow dish of water and let the soil soak it up. This prevents damping-off disease and keeps the seedlings healthy. In the Desert Southwest, our spring weather can be very-early and changeable, so starting indoors provides some protection.

Transplant your bok choy seedlings outdoors from mid March through late April, once they have a few true leaves and the risk of frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. Start with an hour or two of shade, increasing the time each day.

Plant seedlings 6-10 inches apart in well-draining soil. Even in spring, be prepared for unexpected warm spells. Shade cloth can be useful if temperatures climb quickly.

Direct sowing is a simple way to grow bok choy, especially for the fall harvest. Sow seeds directly into the garden from early March through mid September. Ensure the soil is well-prepared and consistently moist, as bok choy needs moisture to germinate.

Plant seeds about ¼ inch deep and thin seedlings to 6-10 inches apart once they emerge. Direct sowing in the Desert Southwest works best when the soil temperature is consistently cool, making fall the ideal time.

Bok choy needs consistent moisture to thrive, especially in our arid Desert Southwest climate. Aim to keep the soil consistently moist, but not waterlogged. A good rule of thumb is to water deeply whenever the top two inches of soil feel dry to the touch – the "finger test."

During the spring and fall, water deeply about 1-2 times per week, providing about 1 inch of water each time. During the monsoon season, you may need to adjust your watering schedule based on rainfall. Water at the base of the plants to avoid wetting the leaves, which can lead to fungal issues in our climate.

Signs of underwatering include wilting leaves and slow growth. Overwatering can cause yellowing leaves and root rot. A layer of mulch around your plants helps retain moisture and keep the soil cool, which is especially important during our hot spells.

You can expect your first harvest of bok choy from mid April through late November, about 45 days after planting. You can harvest baby bok choy when the leaves are 6-8 inches tall for a more tender flavor. For larger, more mature leaves, wait until the plant reaches 12-15 inches.

To harvest, cut the entire plant at the base or harvest individual outer leaves for continuous production. Cutting above the base allows the plant to regrow for a second harvest. As the first frost approaches in mid- November, harvest any remaining bok choy to prevent frost damage.

Here are common problems you might encounter with bok choy in the Desert Southwest:

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: Small jumping beetles that feed on leaves, particularly damaging to small, young plants. They thrive in warm, dry conditions.
• How to fix/prevent it: Use row covers to protect seedlings. Delay planting until plants are larger and more resilient. Apply kaolin clay to create a protective barrier. Neem oil spray can help control infestations. Interplant with basil or catnip to deter beetles.

Cabbage Worms

• What it looks like: Smooth green caterpillars chewing irregular holes in leaves. You might see dark green droppings and white cabbage butterflies fluttering nearby.
• What causes it: Larvae of white cabbage butterflies. They can have multiple generations per season in our warm climate.
• 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 butterflies. Encourage parasitic wasps, which prey on cabbage worms.

Slugs

• What it looks like: Irregular holes in leaves, especially on low-growing plants. Silvery slime trails on leaves and soil. Damage is often worse at night.
• What causes it: 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). Apply iron phosphate bait, which is pet-safe. Remove hiding spots like mulch 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 also works.

Bolting in Heat

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

Desert Southwest Specific Challenges: The extreme heat and arid humidity of the Desert Southwest make bok choy vulnerable to bolting and moisture stress. Consistent watering, shade cloth during the hottest parts of the day, and careful monitoring for pests are essential for success. While monsoon season can help, be aware of fungal diseases due to increased humidity.

Good companions for bok choy in the Desert Southwest include garlic and onions. These alliums deter pests like aphids and cabbage worms with their strong scent. Beets are also beneficial, as they don't compete for the same nutrients and can help loosen the soil. Lettuce and spinach make good neighbors, as they have similar growing requirements and can provide ground cover to keep the soil cool.

Avoid planting bok choy near strawberries or tomatoes. Strawberries and brassicas compete for the same nutrients. Tomatoes can attract pests that also affect bok choy, increasing the risk of infestation.