The red cabbage (Brassica oleracea var. capitata f. rubra) is a sort of cabbage, also known as red kraut or blue kraut after preparation. Its leaves are coloured dark red/purple. However, the plant changes its colour according to the pH value of the soil, due to a pigment belonging to anthocyanins (flavins). On acidic soils, the leaves grow more reddish while an alkaline soil will produce rather greenish-yellow coloured cabbages. This explains the fact that the same plant is known by different colours in various regions. Furthermore, the juice of red cabbage can be used as a home-made pH indicator, turning red in acid and blue in basic solutions. It can be found in Northern Europe, throughout the Americas, and in China.

Kål (Brassica oleracea), art i släktet kål med många viktiga välkända varieteter. Kål har troligen odlats i Sverige åtminstone sedan vikingatiden. Hos vitkål (var. capitata f. alba), rödkål (var. capitata f. rubra), savojkål (var. sabauda) och grönkål (var. acephala) används bladen, hos blomkål (var. botrys) och broccoli (var. asparagoides) används istället de omvandlade blomställningarna. Hos kålrabbi (var. gongylodes) används stjälken och hos brysselkål (var. gemmifera) unga sidoskott.