There are a number of trees in the birch family, and all have oval-shaped leaves. Some varieties have more rounded leaves, while other varieties have more oblong leaves. Birch leaves are either green or yellow in a healthy tree. Any other color may indicate a problem. Members of the birch family are easily identified by their white, paper-like bark.
Birch tree leaves are green in the summer when the tree is healthy. Birch leaves are darker green on top and a lighter green on the bottom. Birch leaves are usually a lighter green as they burst from the buds. The tops darken as the leaves mature. The green color in the leaves is because of chlorophyll, the chemical in tree leaves and other green plants that convert sunlight and carbon dioxide into energy for tree life and growth.
Birch leaves begin to turn yellow in early fall and become a golden yellow when at their showiest. The leaves turn yellow due to a chemical reaction that begins as fall temperatures drop and days become shorter. The color begins to change as the tree loses its ability to produce chlorophyll to replace chlorophyll that is naturally lost during photosynthesis, the process that trees use to produce energy from sunlight. As this chlorophyll dies, other natural colors in the leaves become more prominent. In birch trees, this color is yellow.
Brown leaves on a birch tree are an indication of a problem with the tree. In some cases, summer yellowing of a tree before other trees begin to yellow in the fall can indicate a problem with birch borers. The brown birch borer will often result in an early yellowing of the leaves that quickly turn brown. Any leaves that turn brown on your birch are dead leaves. In the winter, it is natural to see some brown leaves still clinging to the tree. However, at other times of the year, brown leaves indicate that you should have your tree examined for disease or pests.