The
red cabbage (purple-leaved varieties of
Brassica oleracea Capitata Group) is a kind of
cabbage, also known as
purple cabbage,
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. In acidic soils, the leaves grow more reddish, in neutral soils they will grow more purple, 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 green/yellow in basic solutions. It can be found in Northern Europe, throughout the Americas, and in China.