Bok Choy in Zone 3B — Mountain West

Bok Choy is a fantastic addition to any Mountain West garden. Its crisp, mild flavor shines in stir-fries, soups, and salads, and the satisfaction of harvesting your own fresh greens, especially after our long winters, is unbeatable. Plus, cool nights even in summer actually improve the taste!

Our high altitude, short growing season, and intense sun present challenges, but careful timing and a few tricks make growing Bok Choy totally doable. With our 108-day growing season, you can easily squeeze in a spring and fall crop.

Starting Bok Choy indoors is possible, but generally not necessary given our short season and Bok Choy's quick growth. If you want a *really* early start, aim to sow seeds indoors from mid-April through mid-May, about four weeks before you plan to transplant.

Use seed trays or small pots filled with a good seed-starting mix. Keep the soil consistently moist by bottom watering—set the tray in a shallow dish of water and let it soak up from the bottom. Provide warmth and plenty of light, especially important with our late springs, so seedlings don't get leggy searching for sun.

Transplant your Bok Choy seedlings outdoors from late May through early July, after the risk of hard frost has passed. Before transplanting, 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 plants 6-10 inches apart. Be prepared for potential temperature swings common in late spring. Cover young transplants with row covers if a cold snap is predicted.

Direct sowing Bok Choy is a great option, especially for a fall crop. Sow seeds from mid-May through mid-July. Make sure the soil is well-drained and the soil temperature is at least 50°F.

Plant seeds about ¼ inch deep and space them 6-10 inches apart. Keep the soil consistently moist until germination. Thin seedlings to the strongest plant per space. One advantage of direct sowing is that the plants avoid transplant shock.

Watering is crucial for Bok Choy in our dry Mountain West climate. Consistent moisture prevents bolting and ensures tender, flavorful leaves.

During the spring and fall, when temperatures are cooler, water deeply once or twice a week, providing about 1 inch of water each time. In the heat of summer, you may need to water every other day or even daily, especially if it hasn't rained. Use the finger test: stick your finger about 2 inches 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 attract pests and diseases, though our low humidity helps mitigate this. 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 shredded bark, helps retain moisture and regulate soil temperature.

You can expect your first Bok Choy harvest from late June through mid-September, about 45 days after planting. Harvest baby Bok Choy when the leaves are 6-8 inches tall for a more delicate flavor, or wait until the heads reach 12-15 inches for full size.

To harvest, cut the entire head above the base, leaving the roots intact. This allows the plant to potentially regrow for a second, smaller harvest. Regularly harvesting outer leaves encourages continued production.

As the first frost approaches in early September, harvest any remaining mature heads. Even if a light frost nips the leaves, they're still edible, but prolonged freezing will damage them.

Here are some 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 might see small, dark beetles jumping when disturbed.
• What causes it: Small jumping beetles that feed on leaves. They're most damaging to small, young 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 spraying plants with kaolin clay or neem oil. Interplanting with basil or catnip can also help deter them.

Cabbage Worms

• What it looks like: Smooth green caterpillars on brassica leaves. Irregular holes chewed in the leaves, and you might notice dark green droppings. White butterflies hovering around your plants are a giveaway.
• What causes it: These are the larvae of white cabbage butterflies.
• How to fix/prevent it: Bt spray is very effective. Use floating row covers to prevent butterflies from laying eggs. Handpick caterpillars when you see them. Planting aromatic herbs like thyme and sage nearby can help repel them.

Slugs

• What it looks like: Irregular holes in leaves, especially on low-growing plants. Look for silvery slime trails on leaves and soil. Damage is usually worse at night and in wet weather.
• What causes it: Slugs are gastropods that feed at night in moist conditions.
• How to fix/prevent it: Try beer traps (shallow dishes of beer sunk into the soil). Iron phosphate bait is also effective and pet-safe. Remove any hiding spots like boards or debris. 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, and the leaves become tough and bitter.
• What causes it: Extended warm temperatures. Bok Choy is a cool-season crop and bolts when days consistently exceed 80°F.
• How to fix/prevent it: Time your plantings for cooler weather in spring and fall. Choose bolt-resistant varieties. Provide shade during warm spells. Mulch to keep the soil cool. Harvest before bolting progresses too far.

Mountain West Specific Challenges: Our intense sun can scorch leaves if plants aren't properly hardened off or shaded during the hottest part of the day. The low humidity can help reduce disease pressure, but it also means you need to be vigilant about watering.

Good companions for Bok Choy include garlic and onions, whose strong scent repels pests. Beets also work well, as they don't compete for the same nutrients. Lettuce and spinach make good neighbors, filling in space and providing ground cover to keep the soil cool. Avoid planting Bok Choy near strawberries or tomatoes. Strawberries can attract slugs, and tomatoes compete for similar nutrients, potentially stunting growth.