Grow or die
To grow thicker, the tree relies on its cambium, a thin layer of living cells located much closer to the outside of the trunk than the inside. Like the meristematic (Tissue composed of cells able to divide into new specialized tissues.) cells of buds and roots, cambial cells are able to multiply. These new cambial cells become sapwood (Outer layers of wood of the tree trunk, between the heart and the bark.) or secondary phloem (Phloem tissue formed by the cambium during secondary growth.), part of the bark.
This type of secondary growth is only found in trees that meet the classic definition. Monocotyledons (Flowering plants whose seeds have one cotyledon.) (palms, bananas, bamboo) and tree ferns have developed their own solutions, unique and different, in order to grow in height.
