The red cabbage is a kind of cabbage, also known as Blaukraut after preparation. Its leaves are colored dark red/purple. However, the plant changes its color 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. It can be found in all Europe, throughout the Americas, in China and especially in Africa.
The juice of red cabbage can be used as a home-made pH indicator, turning red in acid and green/yellow in basic solutions. On cooking, red cabbage will normally turn blue; it is necessary to add vinegar or acidic fruit to the pot to retain the cabbage's red color.
Red cabbage needs well fertilized soil and sufficient humidity to grow. It is a seasonal plant which is seeded in spring and harvested in late autumn. Red cabbage is a better keeper than its "white" relatives and does not need to be converted to sauerkraut to last the winter.