Cruciferous plants belong to a large genus, botanically. Usually Brassica crops can be subdivided according to the plant organs used; these which develop underground (Beta) and those which develop aboveground (cabbage).
The various cruciferous plants came from various intermediary forms of crossing and selection from Brassica rapa ssp. Campestris and other Brassica-species and varieties, including the long-time oil supplier rapeseed. A subspecies, the rutabaga Brassica napus rapifera, has a thickened lower stem. There is also another mustard species Brassica rapa rapa, which was also cultivated for a long time. The distinction between “Napen” and “Rapen” often isn’t clear cut in historical documents or images. According to use mustards can be subdivided into a white meat and a yellow meat form, but are clearly distinct from the genus Beta. cruciferous plants typically had a low reputation as food, but in times of scarcity often were rescuers in emergencies.
Despite this there are some types with good taste, which are still beloved today and give some meals their characteristic flavour.
Sources: 04-NAP-P85: Kohlrabi und Bodenkohlrabi. Sichtung 2011; Artha Samen