This is a variety of red cabbage called ‘Roodkop’.
Have you ever wondered why red cabbage is red / purple?
Red cabbage leaves contain anthocyanin or a water soluble colour that appears red, blue or purple depending on the pH level of the soil. So if you would like to naturally test the pH of your soil and are not in a rush to find out, this is the vegetable for you.
In acidic soil, the cabbage leaves will be more of a red colour but if your soil is neutral or more alkaline the leaves will have a blue or purple colour, as you can see in this photo. The soil in our garden is very acidic – this is why I grow most vegetables in raised beds.