The parts of a tree are similar to the parts of most other plants. All trees have roots, a trunk, branches, leaves, and flowers. Let us explore the parts of a tree in greater detail.
The roots of trees absorb water and nutrients from the soil. They also store sugar in winter so that the tree can produce new leaves in the spring.
Roots anchor the tree deep in the soil. Trees can have either taproots or fibrous roots. Taproots may extend up to 15' into the ground.
With fibrous root systems, almost all of the roots are found within the upper 12" to 18" of soil, because this is where oxygen is most prevalent in the soil.
The trunk of the tree supports the branches and leaves. The trunk contains four layers of tissues that move water and nutrients throughout the tree. We will explore these layers moving from the outside to the center of the tree trunk.
Outer bark is the outer covering of the trunk, branches, and twigs. These are dead phloem cells that protect the tree from insects, disease, and even fire. Over time bark may become quite thick and creviced. Did you know that tree bark is different from one tree species to another?
The phloem, or inner bark, is the thin layer of phloem cells between the cambium and outer bark. The inner bark provides the food supply to the entire tree. Sugars produced in the leaves are transported throughout the tree by the inner bark.
The cambium is the thin layer of actively growing tissue in the tree trunk. The cambium is what produces the growth rings seen when a tree is cut down. Did you know that the trunk of a tree does not actually grow taller? Instead, it grows larger in girth. This is caused by new layers of cambium being grown each growing season. As it ages, cambium will become xylem, phloem, or more cambium.
Xylem, or sapwood, is the lighter colored wood in the trunk and are the youngest layers of wood. The xylem carries water and nutrients from the roots to the shoots of the tree.
As a tree grows, inner xylem cells become inactive and die, forming heartwood. Heartwood is the innermost part of the trunk. This is where sugars and oils are stored in the tree. These stored materials give heartwood a darker color than the other wood in the trunk. Heartwood also gives the tree trunk its strength.
Moving on from the trunk, the crown of the tree consists of the leaves and branches at the top of the tree. The crown of the tree is the site of photosynthesis. Because of the dense leaf foliage, the crown is also the part of the tree that provides the most shade and cooling.