Kale

Kale, also known as leaf cabbage, is a type of cabbage cultivar grown mainly for its edible leaves, though it also serves as an ornamental plant. There are many different cultivars, and they look quite different from one another: leaves can be bumpy, curly, or flat, and colors range from purple to green. The central leaves do not form a head like headed cabbage does. The foliage and centers can be white, red, pink, lavender, yellow-green, or creamy white.

The name "kale" comes from Northern Middle English *cale* (related to Scots *kail* and German *Kohl*), which referred to various cabbages. The ultimate origin is the Latin word *caulis*, meaning "cabbage."

Kale is derived from wild mustard and is considered closer to wild cabbage than most domesticated forms of *Brassica oleracea*. It is usually a biennial plant grown from seed, with a wide range of germination temperatures. It is hardy and thrives in winter, surviving temperatures as low as -15 °C (5 °F). After a heavy frost, kale can become sweeter.

Kale originated in the eastern Mediterranean and Anatolia, where it was cultivated for food by at least 2000 BCE. Curly-leaved and flat-leaved cabbage varieties existed in Greece by the 4th century BC. The Romans called these forms Sabellian kale, and they are considered the ancestors of modern kales. The earliest record of cabbages in western Europe is of hard-heading cabbage in the 13th century. Records from 14th-century England distinguish between hard-heading cabbage and loose-leaf kale. Russian traders brought Russian kale into Canada and then into the United States in the 19th century. USDA botanist David Fairchild is credited with introducing kale to Americans after bringing it back from Croatia, although Fairchild himself disliked cabbages, including kale. At the time, kale was widely grown in Croatia because it was easy to grow, inexpensive, and could desalinate soil.

Kale varieties are differentiated by stem length (low, intermediate, or high) and leaf type. Leaf colors range from light green to green, dark green, violet-green, and violet-brown. Leaf types include curly-leaf (Scots kale, blue curled kale), bumpy-leaf (black cabbage, also known as cavolo nero, Tuscan cabbage, Tuscan kale, lacinato, and dinosaur kale), sparkly-leaf (shiny and glossy), plain-leaf (flat-leaf types like red Russian and white Russian kale), leaf and spear or feathery-type (a cross between curly and plain), and ornamental (less palatable and tougher leaves). Because kale grows well into winter, one variety called "hungry gap" is named after the winter period when little else could be harvested. An extra-tall variety is known as Jersey kale or cow cabbage. Kai-lan, or Chinese kale, is a cultivar often used in Chinese cuisine. In Portugal, bumpy-leaved kale is mostly called "couve galega" (Galician kale or Portuguese cabbage).

Many varieties of kale and cabbage are grown mainly for their ornamental leaves, which are brilliant white, red, pink, lavender, blue, or violet in the interior of the rosette. Types of ornamental kale include peacock kale, coral prince, kamone coral queen, color up kale, and chidori kale. Ornamental kale is edible but potentially less palatable. In 2012, Pizza Hut purchased about 14,000 lbs of kale for use as salad bar decoration. Kale leaves are also increasingly used in vegetable bouquets and wedding bouquets.

Raw kale is 84% water, 9% carbohydrates, 4% protein, and 1% fat. In a 100 g serving, raw kale provides 207 kilojoules (49 kilocalories) of food energy and 3.7 times the Daily Value of vitamin K. It is a rich source of vitamin A, vitamin C, folate, and manganese. It is a good source of riboflavin, pantothenic acid, vitamin B6, vitamin E, and several dietary minerals, including calcium, magnesium, and potassium. Boiling raw kale diminishes most of these nutrients, though values for vitamins A, C, and K and manganese remain substantial.

Kale is a source of the carotenoids lutein and zeaxanthin. Like broccoli and other cruciferous vegetables, it contains glucosinolate compounds such as glucoraphanin, which contributes to the formation of sulforaphane, a compound under preliminary research for potential health effects. Boiling kale decreases glucosinolate levels, while steaming, microwaving, or stir-frying does not cause significant loss. Kale is high in oxalic acid, which can be reduced by cooking. It also contains high levels of polyphenols, such as ferulic acid, with levels varying due to environmental and genetic factors.

Kale chips have been produced as a potato chip substitute. In the Netherlands, a traditional winter dish called "boerenkoolstamppot" mixes curly kale and mashed potatoes, sometimes with fried bacon, and is served with rookworst (smoked sausage). In Northern Germany, a winter tradition called "Kohlfahrt" (kale trip) involves a group hiking through the woods before gathering to eat kale, usually with bacon and Kohlwurst (kale sausage). Kale is considered a Northern German staple and comfort food. In Italy, cavolo nero kale is an ingredient in the Tuscan soup ribollita. A traditional Portuguese soup, caldo verde, combines pureed potatoes, very finely sliced kale, olive oil, and salt, with optional broth and sliced ingredients.