A tree is made up of the crown, heartwood, cambium, xylem, phloem, bark and roots.
A tree is a woody plant that usually is more than 10 feet tall and has one main stem. Although trees come in different shapes and sizes, most have the same basic parts. Each of these parts – from the highest leaves in the crown to the tiny root hairs buried in the soil – plays an important role in the tree’s function and survival.
The crown of the tree is made up of the leaves and branches.
The trunk of the tree supports the crown and serves as a highway for food made in the leaves to travel to the roots and for water and nutrients from the roots to travel to the leaves.
The heartwood of the tree develops as the tree gets older. It is old sapwood that no longer carries sap and gives the trunk support and stiffness. In many kinds of trees, the heartwood is a darker color than the sapwood, since its water-carrying tubes get clogged up.
The cambium is a layer or zone of cells, one cell thick, inside the inner bark. The cambium produces both the xylem and phloem cells. This is where diameter growth occurs and where rings and inner bark are formed.
In the xylem (sapwood) layer, tree sap (water plus nitrogen and mineral nutrients) is carried back up from the roots to the leaves. Sapwood gives a tree its strength.
In the phloem (inner bark) layer, sugar that is made in the leaves or needles is carried down to the branches, trunks and roots, where it is converted into the food (starch) the tree needs for growth.
The bark layer protects the tree from insects and disease, excessive heat and cold and other injuries.
The roots of the tree support the trunk and crown and also anchor the tree in the soil. They serve as a storage facility during the winter for the food produced by the leaves during the growing season. The roots also absorb water and nutrients from the soil for use by the tree.
