Tree growth rings. Cross-section through the trunk of a Laburnum sp. tree (family: Leguminosae) showing the circular bands of growth rings. Also seen is the tree's outer surface (bark). Each of the growth rings represents a year of growth for the tree. Counting these rings reveals the tree's age at felling. This tree can be seen to have been at least 16 years old. The rings can also give information on environmental conditions at the time of growth. Thick rings, for instance, indicate excellent growth conditions for the tree.