Bok Choy in Zone 6B — Mountain West

Bok choy is a fantastic addition to any Mountain West garden. Its mild, slightly sweet flavor and crisp texture make it a versatile ingredient in stir-fries, soups, and salads. Plus, it's incredibly satisfying to harvest your own fresh greens, especially knowing they've thrived despite our intense sun and cool nights.

Growing bok choy in our region does present unique challenges, like high altitude, intense UV, alkaline soil, and a short growing season of only 163 days. But with careful timing and a few tricks, you can enjoy a bountiful harvest.

Starting bok choy indoors gives you a head start, but it's not always necessary. It makes sense if you're eager for an early harvest or want to protect young seedlings from early-season pests.

If you choose to start indoors, sow seeds late March through mid April, about four weeks before you plan to transplant. Use seed trays with a good seed-starting mix and keep them in a warm spot with plenty of light – a south-facing window or under grow lights works well. Bottom watering is a good way to keep the soil consistently moist without damping off. Remember, spring in the Mountain West can be fickle, so be prepared to adjust your schedule as needed.

Transplant your bok choy seedlings outdoors late 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.

Space plants 6-10 inches apart in well-drained soil. Be mindful of the intense sun; if it's a particularly hot spell, provide some temporary shade with row covers or shade cloth for the first few days. Our cool nights are usually a benefit, but watch out for late frosts!

Direct sowing bok choy is a simple and effective method, especially for later crops. Sow seeds mid April through early August, as long as you have about 45 days until your average first frost.

Prepare the soil by loosening it and adding compost. Sow seeds about ¼ inch deep and keep the soil consistently moist. Thin seedlings to 6-10 inches apart once they emerge. Direct sowing avoids transplant shock, but young seedlings are more vulnerable to pests.

Consistent moisture is key for bok choy in our dry Mountain West climate. Unlike some regions, we don't have humidity on our side, so you need to be diligent. Aim to keep the soil evenly moist, especially during warm spells.

Water deeply about 1-2 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. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in some climates, though our low humidity usually keeps that in check.

Underwatering leads to wilting and can cause bolting. Overwatering, though less common in our dry climate, can lead to root rot. Signs of underwatering include drooping leaves that don't perk up in the evening, while signs of overwatering include yellowing leaves and a generally unhappy plant. A layer of mulch, like straw or wood chips, helps retain moisture and keep the soil cool.

You can expect your first harvest of bok choy late May through mid October, depending on when you planted. Baby bok choy can be harvested when the leaves are 6-8 inches tall. For full-sized bok choy, wait until the heads reach 12-15 inches.

To harvest, cut the plant just above the base, leaving the roots intact. This often encourages regrowth for a second, smaller harvest. Bok choy doesn't ripen off the vine, so harvest when it's ready.

As the first frost approaches in early October, harvest any remaining bok choy, even if it's not fully mature. You can use the smaller leaves in salads or stir-fries.

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'll see small dark beetles that jump when disturbed. Damage is worst on young seedlings.
• What causes it: Small jumping beetles that feed on leaves. They love brassicas and are especially damaging to small plants.
• How to fix/prevent it: Use row covers to protect seedlings. Delay planting until plants are larger. You can also try kaolin clay coating or neem oil spray. Interplant with basil or catnip to deter them. Healthy plants can usually 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 fluttering around your plants.
• What causes it: These are the larvae of those white cabbage butterflies.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent the butterflies from laying eggs. Handpick the caterpillars when you see them. Interplant with aromatic herbs like thyme and sage to confuse the butterflies. Encourage parasitic wasps in your garden.

Slugs

• What it looks like: Irregular holes in the leaves, especially on low-growing plants. You'll see silvery slime trails on the leaves and soil. Damage is worse at night.
• What causes it: Slugs are gastropods that feed at night in moist conditions. They hide under mulch and debris during the day.
• How to fix/prevent it: Beer traps work well (shallow dish of beer sunk into the soil). Iron phosphate bait is pet-safe. Remove any hiding spots like boards or piles of leaves. Water in the morning so the soil surface dries out by evening. Copper tape around beds can deter them. Diatomaceous earth around plants is also effective.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk. The leaves become tough and bitter, and the harvest quality declines.
• What causes it: Bok choy is a cool-season crop and bolts when temperatures rise. This happens 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 with shade cloth. Mulch to keep the soil cool. Harvest the plant before bolting progresses too far.

Mountain West Specific Challenges: Our moderate-at-altitude summer heat combined with low humidity and dry rainfall can stress bok choy. Consistent watering is crucial to prevent bolting. The intense UV radiation can also scorch leaves, so providing afternoon shade during the hottest part of the day is a good idea, especially for young plants.

Good companion plants for bok choy in the Mountain West include garlic and onions. Their pungent aroma helps deter pests like flea beetles and cabbage moths. 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 and moist.

Avoid planting bok choy near strawberries or tomatoes. Strawberries can attract slugs, which will also feed on your bok choy. Tomatoes can harbor diseases that can spread to bok choy, and they also have very different nutrient needs, leading to competition in our often-alkaline soil.