The trunk provides support for branches, which in turn support the tree's leaves. They also contain the growing layer of the tree that makes the trunk, branches, and roots of the tree thicker each year. A Heartwood forms the central core of the tree, is made up of dense dead wood, and provides strength for the tree. Roots A tree's roots help anchor the tree in the ground. They also absorb water and nutrients from the soil.
Trees have lateral roots that spread out from the tree and cover a broad area.
Many trees also have a taproot that grows straight into the ground. As a tree's taproot and lateral roots grow away from the tree, they branch into finer and finer roots called rootlets. The rootlets themselves are, in turn, covered by even finer root hairs . These root hairs absorb approximately 95 percent of the water and nutrients absorbed by the tree. Then find a large, open area where the students can build the tree.