As an edible plant in the mustard family, kale has spreading crinkled leaves that do not form a compact head. It is also called borecole, cole, colewort and collard.Kale and collards are similar in many respects, just differing in little more than the forms of their leaves. They are in fact primitive cabbages that have been retained through thousands of years.Kale has been cultivated for more than 2,000 years. In much of Europe it was the most widely eaten green vegetable until the Middle Ages when cabbages became more popular.Kale is a very handy ingredient for seasonal eaters as it is one of the few green vegetables that is more abundant and flavourful during the coldest months of the year.