Atoms, cars and ecosystems all have parts that together make up
the whole. Trees have
the perfect number of parts to survive and thrive in the
environment. Each part has a
primary job to perform.

Everyone can see the biggest tree parts. Trees have twigs and
branches that support the
leaves and buds. The stem supports the branches. The roots
support the stem.

The tree parts few people notice are small, internal components.
When you cut across a
branch with a saw, you cut many tissues or parts. The first part
damaged is the bark.

Bark is an amazing material. The outside bark is made of dead,
air-filled cells that have
been flattened and sealed with a waterproof material.

Think of bark as an oil-covered canvas coat. It’s lightweight.
It floats in water — corks are
made from the bark of an oak tree.

Bark is a good insulator, too. It protects the tree from sudden
changes in temperature and
from heating caused by sunlight.

Bark helps the tree conserve precious moisture by slowing
water’s escape into the air. But
it must also allow for oxygen to move inward and carbon dioxide
to escape.

Bark’s the first barrier to breach, too, when a pest attacks a
tree. Without healthy bark,
trees would be dry, suffocated and diseased.

Beneath the dead bark layers are living cells that produce bark.
Beneath these cells is a
layer of transport cells called the phloem. This is sometimes
called inner bark.

Phloem is responsible for moving food and other growth materials
made in the leaves to
all the other parts in a tree. It’s the major transport highway
in a tree.

The phloem is made by special cells that split apart, producing
two new cells — one to the
outside and one to the inside. The new cells split off to the
outside become phloem. The
ones split off to the inside become xylem, the wood inside a
tree.

Both phloem and xylem come from the same mother cells. These
special mother cells are
an area called the cambial zone, a major growth and reaction
center in a tree.

This cambial zone responds to changes in the environment by
producing more or fewer
cells of different types and with different characteristics.
It’s responsible for a tree’s yearly
expansion in girth.

When you cut into the wood, the outer protection layer (bark),
food transport connections
(phloem) and growth layer (cambial zone) are all severed.
Remember, the most exterior
parts of a tree are responsible for its life.

Those are the parts people most easily damage, too. The bumps,
bruises and nicks of daily
life, many of which we may consider minor, can add up to be life-
threatening in a tree.

The inner portion of a branch, stem or root is made of xylem.
The xylem area is a
combination of parts that act as transport pipes, strength
fibers and living helper cells.

Xylem pipes transport water, essential elements and growth
materials from the roots to the
leaves. The fiber cells provide strength, keeping the stem
upright against gravity and wind.
The living helper cells store food, react to damage and
transport needed growth materials
for short distances.

If you don’t know tree parts and how they work, it’s hard to
understand a whole tree. A
tree is a single, highly integrated and specialized creature.

Trees must stand against an environment trying to knock them
down and neighbors trying
to consume them. You can help them survive and thrive by
appreciating their parts,
knowing how they work and preventing tree damage.