Partial shade can help prevent summer crops from bolting.

Prefers well-drained, fertile soil high in organic matter, pH 6.0 to 7.5. Can tolerate slightly alkaline soil. Needs plentiful, consistent moisture.

Biennial grown as an annual.

Spring crops require good timing and careful pest control. Direct-seeded fall crops are easier to grow.

MAINTAINING
While not as sensitive to heat and cold as Chinese cabbage, spring crops may bolt prematurely if young plants are exposed to frost or a week of nighttime temperatures below 50 F. Wait until after last frost date to direct seed or transplant out.

Start transplants inside 4 to 6 weeks before last frost date. Transplant 6 to 12 inches apart in rows 18 to 30 inches apart. Use the closer spacings for smaller varieties.

Plant direct-seeded spring crops ¼ to ½ inch deep and about 1 inch apart in rows 18 to 30 inches apart. Thin to 6- to 12-inch spacings. Use thinnings in salads.

For fall crops, direct seed ¼ to ½ inch deep in rows 18 to 30 inches apart in summer. Thin to 6- to 12- inch spacings. Or set transplants out at 6- to 12-inch spacings 4 to 6 weeks before first frost.

Mulch fall crops heavily and provide adequate moisture to avoid premature bolting.
    
HARVESTING
“Baby” bok choy is used to describe both the dwarf Canton bok choy and other bok choys picked small and immature.

When you harvest bok choy, be sure to do it before the hot weather sets in with your first crop. Hot weather tends to make the bok choy go into seed very quickly. These are the first plants in the garden each spring because they can survive temperatures below 30 degrees F. Because you will be planting bok choy early, you will be harvesting it early as well.

Bok choy is a non-heading cabbage. It grows close together with leaves and stalks much like celery. You will want to harvest bok choy when it reaches twelve to eighteen inches tall. This vegetable is great in soups, salads and stir-fries. It is very fresh, crisp and versatile.

http://www.heirloom-organics.com/guide/va/guidetogrowingbokchoy.html