The importance of being red

Hooray for anthocyanin. Where would we be without it? It has long been my favourite water-soluble, vacuolar, glucosidic pigment, and I feel that this autumn has justified my preference. True, chlorophyll is more important until then, being essential for photosynthesis, so we should all be in dead trouble without it; and the carotenoids, carotene and xanthophyll, are often more obvious to us, because of the delicious golden yellow to which many native shrubs — field maple, elm suckers, and blackthorn — turn in autumn. However, even at that time of year, anthocyanin just gets my vote, because it produces the most beautiful of crimson-lake and purple tints in aging leaves. My paperbark maple, Acer griseum (see picture), was remarkable for the depth and warmth of its leaf colour — until the gales in the second weekend in November stripped it almost bare, that is.

We gardeners talk of anthocyanin in the singular but, in truth, there are more than 300 different anthocyanin compounds. The distinctions matter only to scientists; we need only know that they occur in the tissues of a wide range of plants, and are responsible for purple and deep red colours in stem, leaf and fruit. It is thought that anthocyanins are ‘photo-protective’, in other words, they shield plant tissue from strong sunlight.

That is not the half of it, however, for it is now well-established that anthocyanins are powerful antioxidants, and that fruits and vegetables, which are high in them, help mammals to fight aggressive tumours, such as colon cancer, as well as heart conditions, diabetes and degenerative conditions associated with old age. What is more, you don’t have to be a plant scientist to work out which these fruit and vegetables might be: the deep-coloured ones like blackcurrants, blueberries, bilberries, cranberries, blackberries, raspberries, red grapes, purple-sprouting broccoli and red cabbage.