Black bearberry (Arctostaphylos alpina) in autumn. Anthocyanins are responsible for the red and purple foliage of this plant. In late summer phosphates and other chemicals are withdrawn from the leaves into the stems. The sugar breakdown process is altered which results in the production of anthocyanin pigments in leaf sap cells. In some plants anthocyanins and carotenoids, which are present throughout the growing season, combine to extend the colour spectrum of autumn. The brilliance of the colours is dependant on the temperature. Cold, but not freezing conditions, being the best. Black bearberry, a procumbent shrub, is a member of the heather family. In autumn the leaves are red and the berries turn black.