Loose-leafed, edible plant ( Brassica oleracea , Acephala group) derived from the cabbage , in the mustard family .
Common (or Scotch) and Buda kale have stems up to 2 ft (60 cm) long that carry a rosette of elongated, dark bluish green, wavy or frilled leaves. Grown mainly for autumn and winter harvest because cold weather improves the quality of this hardy vegetable, kale is usually served cooked. It is highly nutritious. See also collard .