This vegetable is a member of the turnip family and, for that reason, is also called cabbage turnip. Like the turnip, both the bulblike stem and greens are edible. There are two varieties of kohlrabithe green type has a pale green bulb and green leaves with light green veining; purple kohlrabi has a purple root, stems and veining on green leaves. The flesh on both varieties has a creamy white color and a flavor reminiscent of a sassy-sweet blend of mild broccoli and celery root. The leaves have a flavor akin to that of collard greens. Kohlrabi is available year-round and ranges from golf-ball to tennis-ball size. The smaller the root, the younger and more tender the kohlrabi. Choose a kohlrabi that is heavy for its size with firm, deeply colored green leaves. Avoid any with soft spots on the bulb or signs of yellowing on leaf tips. Separate the leaves from the bulbs; the former can be refrigerated in a plastic bag for up to 4 days, the bulbs for up to 10 days. Just before using, peel the bulbs; wash the greens in several changes of cold water, blotting dry on paper towels. Kohlrabi can be eaten raw or added to soups, stews and stir-fry dishes. It's rich in potassium and vitamin C.