Why Do Leaves Turn Brown in the Fall?
The leaves of trees turn brown in autumn when they lose a green substance called chlorophyll. All spring and summer the leaves on a tree use the pigment chlorophyll and sunlight to make food so that the tree can grow.
Chlorophyll is the green dominant pigment in leaves during the spring and summer. The green pigment hides the other colors in the leaf.
But in the fall, when there is less and less sunlight, a layer of cork forms at the base of each leaf stem. It blocks the tiny pipelines that carry water into the leaf.
Without water the leaf dies. The green chlorophyll disappears, and the leaf turns brown. In the spring new leaves will grow, full of green, life-giving chlorophyll.