Kale is a non-heading leafy wild cabbage. Differentiate between varieties according to the low, intermediate, or high length of the stem, with varying leaf types ranging from wavy to straight and frilly. An excellent source of vitamin C, kale provides iron, vitamin A, calcium, magnesium, potassium, protein, carbohydrates and dietary fiber. One half cup of chopped boiled kale contains about 18 calories. Eat with fish, poultry and meats to enhance iron absorption.