Bok Choy in Zone 9B — Desert Southwest

Bok choy is a fantastic addition to your Desert Southwest garden, offering a mild, slightly sweet flavor that’s delicious stir-fried, steamed, or even added raw to salads. Its quick growth cycle means you can harvest it in both your spring and fall growing seasons, adding fresh greens to your table when other crops are struggling in the extreme heat.

While our desert climate certainly presents challenges—extreme heat, intense sun, and alkaline soil—growing bok choy is absolutely doable with careful timing and a few smart strategies. Our long 313-day growing season gives you ample opportunity to enjoy this versatile vegetable.

Starting bok choy indoors gives you a head start, especially for that early spring harvest. Begin sowing seeds indoors from early to late January, about four weeks before you plan to transplant. Use seed trays with a good seed-starting mix and keep them in a warm location with plenty of light—a sunny windowsill or under grow lights works well.

Bottom watering is your friend in our dry climate; it helps prevent damping-off and keeps the seedlings evenly moist. Place the tray in a shallow dish of water until the surface of the soil is moist. Given our very-early spring character, this indoor start can help you get a jump on the season.

Transplant your bok choy seedlings outdoors from early February through mid March, after hardening them off for about a week. "Hardening off" means gradually exposing them to outdoor conditions, starting with a few hours of shade each day and slowly increasing the sun exposure.

Space the seedlings 6-10 inches apart in well-draining soil amended with compost. Even in February, be prepared for temperature swings; keep an eye on the forecast and protect young plants with row covers if a cold snap threatens.

Direct sowing bok choy is a viable option, especially for your fall crop. Sow seeds directly into the garden from late January through mid October, planting them 1/4 inch deep and spacing them 6-10 inches apart.

Make sure the soil is well-prepared and consistently moist, as bok choy needs consistent moisture to germinate. Direct sowing is convenient, but be aware that seedlings are more vulnerable to pests like flea beetles, so monitor them closely. Soil temperatures should be at least 50°F for best germination.

Bok choy needs consistent moisture to thrive, especially in our arid Desert Southwest climate. Aim to keep the soil consistently moist but not waterlogged, as fluctuations in soil moisture can cause bolting.

During the spring and fall growing seasons, water deeply about 2-3 times per week, providing roughly 1 inch of water each time. Use the "finger test"—stick your finger into the soil about 2 inches deep; if it feels dry, it's time to water. During our monsoon season, adjust your watering schedule based on rainfall, but don't rely on monsoon moisture alone.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our occasionally humid monsoon season. Signs of underwatering include wilting leaves and slow growth, while overwatering can lead to yellowing leaves and root rot. A layer of organic mulch, like straw or wood chips, helps retain moisture and keep the soil cool.

You can expect your first bok choy harvest from early March through late December, depending on when you planted. Bok choy is ready to harvest about 45 days after planting.

Harvest baby bok choy when it reaches 6-8 inches tall for a more tender flavor. For full-sized bok choy, wait until it reaches 12-15 inches. To harvest, cut the plant above the base, leaving the roots intact. This allows the plant to regrow and produce additional leaves for a continuous harvest.

As our first frost approaches in mid- December, harvest any remaining bok choy, even if it's small. You can blanch and freeze extra bok choy to enjoy throughout the winter months.

Flea Beetles

• What it looks like: Tiny, round holes (shot-hole pattern) in the leaves, especially on young seedlings. You might see small, dark beetles jumping when disturbed.
• What causes it: These small jumping beetles love to feed on brassicas. They're most active during warm, dry weather, which we have plenty of in the Desert Southwest.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. Delay planting until plants are larger and stronger. Kaolin clay coating can deter them. Neem oil spray can also help.

Cabbage Worms

• What it looks like: Smooth green caterpillars chewing irregular holes in the leaves. You might also see dark green droppings on the leaves and white butterflies fluttering around.
• What causes it: These are the larvae of cabbage butterflies. They thrive in our warm climate, producing multiple generations per season.
• How to fix/prevent it: Bt spray is very effective against cabbage worms. Use floating row covers to prevent the butterflies from laying eggs on your plants. Handpick the caterpillars when you see them.

Slugs

• What it looks like: Irregular holes in the leaves, especially on lower leaves. Silvery slime trails on the leaves and soil are a telltale sign.
• What causes it: Slugs are gastropods that feed at night in moist conditions. They hide under mulch and debris during the day. While our climate is dry, monsoon season can provide enough moisture for slugs to become a problem.
• How to fix/prevent it: Beer traps (shallow dishes of beer sunk into the soil) can lure and drown them. Iron phosphate bait is a pet-safe option. Remove hiding spots like rocks and boards. Water in the morning so the soil surface dries out by evening.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk prematurely. The leaves become tough and bitter, and harvest quality declines.
• What causes it: Bok choy is a cool-season crop and bolts when temperatures rise. This is a major concern in the Desert Southwest, where we experience extreme heat.
• How to fix/prevent it: Time your plantings for the cooler parts of the year (spring and fall). Choose bolt-resistant varieties. Provide shade during warm spells with 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 particularly susceptible to bolting and stress. The monsoon season can bring temporary relief but also create conditions favorable for pests and diseases. Careful monitoring, strategic watering, and shading are crucial for success.

Good companions for bok choy in the Desert Southwest include garlic and onions. These alliums help 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 improve soil structure. Lettuce and spinach can be planted nearby as they have similar growing requirements and can help shade the soil, keeping it cooler.

Avoid planting bok choy near strawberries or tomatoes. Strawberries can attract slugs, which will then move on to your bok choy. Tomatoes can compete for nutrients and water, especially in our dry climate, stressing both plants.