Annual Growth Rings: Oak trees have two growing seasons, Spring and Summer. The growth that takes place each season can be seen in the growth rings to the inside of the cambium. Because there is more rainfall in the spring, the wide, light colored rings are cells that were produced in the spring growing season. These cells carried large amounts of water to the tree’s leaves. Because there is less rainfall, cells produced in the Summer are smaller and create thin, dark rings. The age of a tree can be calculated by counting the number of rings. One light spring ring and one dark summer ring are created each year. This tree was approximately 138 years old when it died!