Ask Mr Brain...all will be explained

Do trees ever stop growing? The answer is no. Trees may die from disease, a lack of nutrients or sunlight, insect attacks or being cut down. But as long as they survive, they will never stop growing.

Growth involves the formation and expansion of new cells, tissues or organs. Trees grow at different rates, and different parts of a tree start growing at different times.

Every year, trees put out new shoots at the tips of their branches and grow new leaves and get bigger.

The reason that trees continue to grow, and humans don't, is that tree cells have a special characteristic known as 'totipotency' - the ability of cells to form different kinds of cells, cells unlike themselves.

Our eye cells will always be our eye cells, and our liver cells will always remain as liver cells. But plant cells can develop into whatever cells the plant needs. Therefore, as parts of the tree dies, other parts can produce new parts to replace them.

The oldest kind of tree is the bristlecone pine, which grows in the western United States. It has been found to be as old as 4,900 years. The oldest surviving plant is the creosote bush. Scientists have found one which they think is more than 12,000 years old.