Baby bok choy grows very quickly and is usually ready for harvest in just over a month. Sow under protection 4-6 weeks before last frost; transplant 3 weeks before last frost. Sow successively. Fall crops are most successful: sow July-August. Spring-sown crops must be harvested young to beat bolting; they also may need row cover to protect against flea beetle damage. All Asian mustards will overwinter with protection and give delicious greens through January, at least.