Growth of a Tree

A tree grows through the tops of branches. Just within the inner bark, the tree becomes thicker by the formation of cells. A young tree grows taller and thicker every year. The growth is rapid during spring and slower during late summer and early fall. In young trees, hollow cells are alive. During the growing season the cells are filled with sap, which circulates through each fibre by a series of openings and connecting channels. With time, the older channels become partly clogged and inactive and more mature tissues combine to form the heavier and stronger heartwood. Active growth takes place only in the cells of the inner bark. As long as the layer of cells just within the outer bark is healthy, growth continues. A few annual rings next to the inner bark are less mature, which is known as sapwood. Heartwood is more resistant to decay than sapwood.