Freezing temperatures greatly reduce the brilliance of autumn color by killing or severely injuring the leaves, preventing physiological processes before the pigments reach their maximum development. The mythical Jack Frost who supposedly brings reds and purples to autumn trees by pinching the leaves with his icy fingers actually does more harm than good. In Review Both hardwood and conifer trees develop fall color. Chlorophyll is a green pigment in chloroplast necessary for photosynthesis. Carotenoids are assessory pigments for photosynthesis, located in chloroplast and give yellow and orange colors.
Tannins are waste products of cell processes found in vacuoles and cell walls, giving brown colors.
Anthocyanins are complex and numerous pigments generally produced in the fall from sugars and responsible for pink to purple colors. Abscission layer is a zone formed by collapse of phloem cells, trapping sugars in leaves and the point where a leaf is shed from a twig. Best weather condition for autumn color are bright sunny days and cool nights. Issued in furtherance of the acts of May 8 and June 30, 1914.