A tree grows mostly during the springtime, when there is plenty of rain and sun
to nourish it. It starts its spring growth by dividing a layer of cells known
as the cambium that lay between the old wood and the tree's bark. This first
growth, called earlywood, is light colored. As the growth rate slows and stops
during fall the cells laid down are smaller and denser (and therefore appear
darker). This layer, called latewood, marks the end of the growing season. The
area from the beginning of the earlywood and end of the latewood periods
represent one year of growth.
Not all trees form rings—they only occur in trees that have a down time when
they do not grow, such as fall and winter. Trees in the tropics that grow
year-round do not form annual rings.
A tree grows mostly during the springtime, when there is plenty of rain and sun
to nourish it. It starts its spring growth by dividing a layer of cells known
as the cambium that lay between the old wood and the tree's bark. This first
growth, called earlywood, is light colored. As the growth rate slows and stops
during fall the cells laid down are smaller and denser (and therefore appear
darker). This layer, called latewood, marks the end of the growing season. The
area from the beginning of the earlywood and end of the latewood periods
represent one year of growth.