A tree never permanently stops growing as long as it lives. But in most countries each year’s growth is ended during the cold and dry season. The annual period of growth depends on the climate. In most tropical regions a tree may grow continuously.
Every period of growth is marked by an annual ring. This ring takes the form of a new layer of wood added to the width of the tree. So the age of a tree may be calculated. Some trees, notably the Redwood trees of California, are said to live for 4,000 years.