The acephala group refers to any type of Brassica which grows without the central 'head' typical of many varieties of cabbage.

This group includes a number of species, both wild and cultivated, many of which are grown for their edible leaves and flowers.

Different sources break down the Brassica genus into different grouping as shown below: Mabberley (q.v.)

Each cultivar has a different genome owing to mutation,[13] evolution, ecological niche,[14] and intentional plant-breeding by humans.

Mabberley (1997, p. 120) has the Acephala group in three sub-groups: kale, borecole, and collards.