The acephala group refers to any type of Brassica which grows without the central 'head' typical of many varieties of cabbage. These are included within the species Brassica oleracea, such as kale. The name literally means "without a head" in contrast to those varieties known as capitata or "with a head". This group includes a number of species, both wild and cultivated, many of which are grown for their edible leaves and flowers.

Brassica oleracea is a plant species from family Brassicaceae that includes many common cultivars used as vegetables, such as cabbage, broccoli, cauliflower, kale, Brussels sprouts, collard greens, Savoy cabbage, kohlrabi, and gai lan.