Freeze any surplus. Harvest head after the first moderate frost in the fall and store in perforated plastic bags in the refrigerator, cold cellar or outdoor pit. Chinese cabbage will keep for up to 2 months. Harvest spring cabbage when heads solidify but before a seed stalk forms. For standard types, harvest when the swollen stems are 2 to 3 inches in diameter.
Stems become woody if left too long before harvest or if grown under poor conditions.
Giant, heirloom types may reach 1 foot in diameter and still retain high quality. Cut off root and leaf stems and store in plastic bags as indicated for carrots. Storage life is 2 to 4 weeks. Merely break off the outer leaves. Swiss chard is a beet relative developed for its top.