Kale is an archaic type of cabbage that grows loosely furled leaves, rather than forming a head. The leaves have a distinctive ruffly appearance that distinguishes the plant from a close relative, collard greens. This vegetable tends to be a little bit bitter in flavor, although this bitterness is tempered by washing, cooking, and using younger leaves. It is also extraordinarily nutritionally rich, even among the leafy green vegetables.
People have cultivated this plant for over 3,000 years; and it was extremely popular in ancient Greece and Rome. In medieval times, kale was sometimes the only vegetable eaten, because it was easy to grow, tolerant to cool climates, and delicious. While it is less popular than headed cabbage, Brussels sprouts, and other relatives, the plant has numerous merits that are beginning to endear it to consumers again.
Most kale is eaten cooked, although very young leaves may be trimmed from the stalks and used raw in salads. When cooked, it can be mixed in with soups, used in mashed potatoes, roasted on pizza, and eaten plain as a side dish. It's important to be aware that the stems take more time to cook than the more delicate leaves. Some cooks trim out the largest stems to be cooked longer or discarded, to avoid soggy leaves and woody stems.
Kale is rich in calcium, vitamin K, folic acid, magnesium, and beta carotene. It lends itself to a wide variety of recipes and is delicious sauteed, steamed, grilled, or fried, plain or ornamented with olive oil, salt, lemon, or butter. It can be used as a stand in for other leafy greens, such as spinach in quiche, or added to stir fries and soups.
These vegetables are extremely hardy, suited to gardening in almost any part of the world. Kale is one of the few greens that takes well to frost, actually tasting sweeter after it has been frost kissed. It should not be planted in the summer, because hot weather makes the leaves woody and more bitter. It's best to plant it in moist, well composted soil approximately 10 inches (25 centimeters) apart, and keep the soil moist so that the leaves stay tender and flavorful. Kale will keep for 14 to 21 days if refrigerated and separated from apples, pears, and other fruits that contain the ripening agent ethylene gas.