Bok Choy in Zone 7A — Mountain West

Bok choy is a fantastic addition to the Mountain West garden. Its mild, slightly sweet flavor adds a unique touch to stir-fries, soups, and salads. Plus, the satisfaction of harvesting your own crisp, vibrant greens is amplified by our intense sunlight, which seems to boost the flavor.

Our short growing season and unpredictable late spring weather can be a hurdle, but with careful timing, you can easily enjoy a bountiful harvest of bok choy. With a growing season of around 173 days, you have a solid window to get this crop established and thriving.

Starting bok choy indoors is an option, but direct sowing often works well in our climate, especially for later plantings. If you want a very early start, sow seeds indoors mid-March through early April, about four weeks before the typical transplant window. Use seed trays with a good seed-starting mix, provide warmth (a heat mat helps), and ensure bright light.

Bottom watering is key to prevent damping off, especially in our drier air. Simply place the tray in a shallow dish of water and allow the soil to absorb moisture from the bottom. Keep in mind that spring can be late in the Mountains.

Transplant your bok choy seedlings outdoors mid-April through early June, once the danger of hard frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This is crucial to prevent shock from our intense sun and temperature swings.

Space plants 6-10 inches apart in well-draining soil. Be mindful of late frosts and hail storms that can still occur during this period, and be prepared to cover your young plants if necessary.

Direct sowing is an easy and effective method for growing bok choy here. Sow seeds early April through mid August for succession planting. Prepare the soil by loosening it and adding compost. Bok choy seeds germinate best when soil temperatures are between 50°F and 70°F.

Sow seeds about ¼ inch deep and space them 6-10 inches apart. Direct sowing saves you the trouble of transplanting, but you'll need to monitor for pests like flea beetles, especially when the plants are small.

Bok choy needs consistent moisture to thrive, but overwatering can be just as detrimental. In our dry Mountain West climate, this requires careful attention. A general guideline is to water deeply once or twice a week, providing about 1 inch of water each time. However, adjust this based on rainfall and soil conditions.

The "finger test" is your best friend: stick your finger about 2 inches into the soil near the base of the plant. If it feels dry, it's time to water. Water at the base of the plant to avoid wetting the leaves, which can encourage fungal diseases in some climates. However, our low humidity makes this less of a concern than in other regions.

Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to yellowing leaves and root rot. A light layer of organic mulch, such as straw or wood chips, can help retain moisture in the soil and regulate soil temperature, which is especially helpful during our brief, intense summer heat.

You can expect your first harvest of bok choy late May through mid October, depending on when you planted. Baby bok choy is ready to harvest when it's about 6-8 inches tall, while full-size bok choy reaches 12-15 inches. Look for crisp, firm leaves with good color.

To harvest, cut the plant above the base, leaving the roots intact. This allows the plant to regrow, giving you multiple harvests. Continue harvesting outer leaves as needed, which encourages the plant to produce more. As the first frost approaches in early October, harvest any remaining bok choy, even if it's smaller than usual. You can blanch and freeze extra bok choy for later use.

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. You might see small dark beetles that jump when disturbed. The damage is worst on young seedlings.
• What causes it: These small jumping beetles feed on the leaves. They're most damaging to small, young plants.
• How to fix/prevent it: Row covers protect seedlings during their vulnerable stage. Delay planting until plants are larger and more resilient. Kaolin clay coating can deter them. You can also try neem oil spray or interplant with basil or catnip. Healthy, vigorous plants often outgrow the damage.

Cabbage Worms

• What it looks like: Smooth green caterpillars on the leaves. You'll see irregular holes chewed in the leaves and dark green droppings. Keep an eye out for white butterflies hovering around your plants.
• What causes it: These are the larvae of white cabbage butterflies.
• How to fix/prevent it: Bt spray is very effective. Floating row covers will prevent egg laying. You can handpick the caterpillars or interplant with aromatic herbs like thyme and sage. Encourage parasitic wasps, which prey on the worms.

Slugs

• What it looks like: Irregular holes in the leaves, especially on low-growing plants. Silvery slime trails on leaves and soil are a dead giveaway. 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.
• How to fix/prevent it: Beer traps (shallow dish of beer sunk into soil) work well. Use iron phosphate bait (which is pet-safe). Remove any hiding spots. Water in the morning so the soil surface dries by evening. Copper tape around beds and diatomaceous earth around plants can also help.

Bolting in Heat

• What it looks like: Your cool-season crop sends up a flower stalk when temperatures rise. The leaves become tough and bitter, and the harvest quality declines.
• What causes it: Extended warm temperatures above the crop's comfort zone. Bok choy bolts when days consistently exceed 80°F.
• How to fix/prevent it: Time your plantings for cool 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 moderate-at-altitude heat, low humidity, and dry rainfall can all impact bok choy. The intense sun can stress plants, making them more susceptible to pests and bolting. Consistent watering is crucial, but our dry air means you need to monitor soil moisture closely.

Good companions for bok choy include garlic and onion. These alliums deter pests with their strong scent. Beets help by improving the soil structure, while lettuce and spinach offer ground cover, helping to retain moisture and suppress weeds.

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