Overview

Kale is a leafy green vegetable in the cabbage family, characterized by its curly or flat leaves that do not form a central head. It has a robust, earthy flavor that becomes sweeter after frost exposure. The plant is a cultivar of Brassica oleracea, the same species that includes broccoli, cauliflower, Brussels sprouts, and collard greens [1].

Origin and history

Kale is considered one of the oldest forms of cabbage, closer to wild cabbage than most domesticated varieties [2]. It was widely cultivated in the eastern Mediterranean and Asia Minor before spreading to Europe. By the Middle Ages, kale was a staple green in Scotland and northern Germany, where it thrived in cold climates [4]. In the United States, kale was reportedly used primarily as a decorative or livestock plant until recent decades, with its rise as a superfood occurring in the early 2000s [3].

Varieties and aliases

  • Curly kale (Scots kale): the most common commercial variety, with tightly ruffled leaves.
  • Lacinato kale (also called Tuscan kale, dinosaur kale, cavolo nero): dark blue-green, flat, savoyed leaves; associated with Italian cuisine.
  • Red Russian kale: flat, fringed leaves with purple stems and veins; milder flavor.
  • Siberian kale: a hardier variety (often classified as Brassica napus) with broad, frilled leaves.
  • The cultivar group Acephala (Greek for “without a head”) includes kale, collard greens, and spring greens [1].

Culinary uses

Kale is eaten raw in salads (often massaged with oil or acid to soften the leaves), sautéed, steamed, baked into chips, or added to soups and stews. It pairs well with garlic, lemon, olive oil, chili flakes, and smoked meats. In Portuguese cuisine, caldo verde is a soup of kale, potatoes, and chouriço. In the American health-food context, kale is blended into smoothies and juiced [3]. The leaves are typically stripped from the tough central stem before cooking.

Cross-cuisine context

Kale has no widely recognized analogue in Mexican cuisine, where the dominant leafy greens are quelites (wild greens such as huauzontle, epazote, and purslane) and nopal (cactus pads). Comparison-by-function: kale’s role as a sturdy, nutrient-dense green that holds up to long cooking is similar to that of collard greens in African American soul food and to malunggay (moringa) leaves in Filipino cooking, where they are added to soups like tinola.

Notes for cooks

  • Kale stems are tough and fibrous; remove them before cooking or save them for stock.
  • Massaging raw kale with olive oil, lemon juice, or salt for a few minutes breaks down cell walls and makes the leaves more tender for salads.
  • Kale stores well in a sealed plastic bag in the refrigerator for up to a week; wash only just before use to prevent wilting.