Brassica rapa chinensis. Pronounced "may-ching-choi." This hybrid Shanghai pac choi is tender, sweet, and crunchy. Short, compact plants are slow to bolt, but also cold-tolerant, for surprisingly long harvest periods. Mei Qing Choi pac choi seeds grow uniformly, with pale green petioles, and lovely, rounded, flat leaves. Perfect for early spring to late fall, and will overwinter with some protection. The secret to success with pac choi is to monitor your crop closely, because the plants can "bolt." This means that at a certain point in its growth season, the plant will send up a flower stock in order for pollination and seed production. This process is incredibly fast with pac choi plants, and can take only two days. Once the flowering process begins, the leaves lose much of their appealing taste and texture. It's best to sow numerous short rows of pac choi at two week intervals, so the whole crop does not mature all at once.