Why are the leaves change colours in the fall?
In preparation for the cold of winter, trees transport sugars and nutrients from the leaves and branches down through the trunk into the roots. Part of the process involves shedding leaves from the previous growing season. Some pigments in the leaves degenerate faster as the leaves die, which explains why different colors appear as the autumn season progresses. First greens and blues degenerate, then the yellow and oranges, and finally the reds. A completely dead leaf has turned brown and should have fallen to the ground.
