Bok Choy in Zone 5B — Mountain West

Bok Choy is a fantastic addition to the high-altitude garden, offering a mild, slightly sweet flavor that's delicious in stir-fries, soups, or even grilled. Its crisp texture holds up well, and it's a nutritional powerhouse to boot. Plus, growing your own in the Mountain West means enjoying truly fresh greens that haven't traveled far, making for a more flavorful and sustainable meal.

Our short growing season and intense sun here in Zone 5B can present challenges, but with careful timing, you can absolutely succeed with Bok Choy. The 149-day season is just right for a couple of crops if you plan well, especially taking advantage of our cool nights that actually enhance the flavor of this veggie.

Starting Bok Choy indoors is definitely an option, especially if you're aiming for an early spring harvest. Begin sowing seeds indoors from late March through late April, about four weeks before you intend to transplant them outside.

Use seed trays or small pots filled with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light, either with a grow light or a very sunny windowsill. Remember to water from the bottom to encourage strong root growth. Keep in mind our late spring means you'll need to watch the weather closely before moving them out.

Transplanting Bok Choy seedlings outdoors should happen between early May and mid June, after the danger of hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Choose a spot with full sun to partial shade, and space the plants 6-10 inches apart. Be prepared for potential late frosts, as our weather can be unpredictable; have row covers ready to protect your young plants if a cold snap threatens.

Direct sowing Bok Choy is a straightforward way to get a crop going. Sow seeds directly into the garden from late April through early August. This allows you to take advantage of the entire growing season.

Make sure the soil is well-prepared and the soil temperature is at least 50°F. Plant seeds about ¼ inch deep, spacing them 6-10 inches apart. Keep the soil consistently moist until germination. Direct sowing is generally less work, but you'll need to watch out for flea beetles that can target young seedlings.

Bok Choy needs consistent moisture to thrive, especially with our dry climate here in the Mountain West. Aim for about 1 inch of water per week, but adjust based on rainfall and soil conditions.

Stick your finger about 2 inches deep into the soil; if it feels dry, it's time to water. Water at the base of the plants to avoid wetting the leaves, which can lead to fungal issues in more humid climates, but isn't as much of a concern for us given our low humidity. In the hotter parts of summer, you might need to water more frequently, even daily, to prevent bolting.

Signs of underwatering include wilting leaves and slow growth. Overwatering, on the other hand, can lead to yellowing leaves and root rot. A good layer of mulch can help retain moisture in the soil and regulate soil temperature, which is especially helpful during our intense summer sun.

You can expect your first harvest of Bok Choy from early June through early October, depending on when you planted. Baby bok choy can be harvested when the leaves are about 6-8 inches tall, while full-size bok choy is ready when it reaches 12-15 inches.

To harvest, cut the plant above the base, leaving the roots intact for potential regrowth. Bok Choy can provide multiple harvests this way. As the first frost approaches in early October, harvest any remaining plants, even if they're not fully mature, to enjoy in your fall meals.

Here are a few common problems you might encounter growing Bok Choy in the Mountain West:

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves, especially on young seedlings. You'll 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. The intense sun and dry conditions can stress the plants, making them more susceptible.
• How to fix/prevent it: Use row covers to protect seedlings. Delay planting until plants are larger and more resilient. Consider a kaolin clay coating. Neem oil spray can also help. Interplant with basil or catnip to deter them.

Cabbage Worms

• What it looks like: Smooth green caterpillars on the leaves. You'll see irregular holes chewed in the leaves, along with dark green droppings. White butterflies hovering around plants are a sign of future trouble.
• What causes it: These are the larvae of white cabbage butterflies. They thrive in our moderate summer temperatures.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent egg laying. Handpick caterpillars whenever you spot them. Interplant with aromatic herbs like thyme and sage to confuse the butterflies.

Slugs

• What it looks like: Irregular holes in leaves, particularly on low-growing plants. Silvery slime trails on leaves and soil are a telltale sign. Damage is 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. Even though we have low humidity, slugs can still be an issue, especially after a rain or heavy watering.
• How to fix/prevent it: Use beer traps (shallow dish of beer sunk into the soil). Iron phosphate bait is pet-safe. Remove hiding spots. Water in the morning so the soil surface dries by evening. Copper tape around beds can also deter them.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk, and the leaves become tough and bitter. Harvest quality declines rapidly.
• What causes it: Extended warm temperatures above the crop's comfort zone. Bok Choy bolts when days consistently exceed 80°F. Our intense sun can exacerbate this issue.
• How to fix/prevent it: Time plantings for cool weather in 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.

Mountain West Specific Challenges: Our moderate-at-altitude heat, low humidity, and dry conditions mean you need to be extra vigilant about watering. The intense sun can quickly dry out the soil, leading to stress and bolting. Consistent moisture is key to healthy Bok Choy in our climate.

Companion planting can definitely give your Bok Choy a boost in the Mountain West garden. Garlic and onions are great companions because their strong scent deters pests like aphids and cabbage moths. Beets are also beneficial, as they help loosen the soil and make nutrients more accessible to the Bok Choy. Lettuce and spinach, being low-growing, can act as a living mulch, helping to keep the soil cool and moist.

On the other hand, avoid planting strawberries and tomatoes near your Bok Choy. Strawberries compete for nutrients and can attract pests that also bother Bok Choy. Tomatoes can stunt the growth of Bok Choy, as they prefer different soil conditions.