For trees to reach full growth, it depends on the climate and the water available. In tropical climates with warm weather and a plentiful supply of water, a tree can become fully grown in 30 years. A tree in cooler regions may take several hundred years to reach full maturity.
Every year a tree grows larger by adding a further layer of wood. These layers are called growth rings. The age of a tree may be calculated precisely by counting these growth rings. The oldest tree in the world is a Great Basin bristlecone pine in California, which is estimated to be 5,064 years old. The age was calculated by taking a core from the trunk of the tree.