Bark & Tree Trunks
Since 6x6's and other timbers are cut from trees, people think of
tree trunks as just being wood. After all they say, how can you hurt
a board? ....it's just wood!
While the center of the trunk is usually
"just wood" (Heartwood), the inner bark consists of living tissue.
These layers are known as the Phloem and the Cambium, with
the cambium being the growth layer.
Inside the Cambium is the
The xylem transports
water and nutrients up the tree, and phloem transports
products of photosynthesis back down.
Because these layers of tissue are just inside the outer bark, it's important to protect this
area from wounds, since these trunk wounds provide an excellent
opportunity for disease pathogens.
Cross section of a tree trunk showing the
xylem, cambium, phloem and outer bark
DON'T heal they
Com - Part - Ment - A - Lize
Trees have a different
way of "healing" wounds. Unlike skin wounds, where our skin cells
regenerate and we heal tissue, trees work to "wall off" or "compartmentalize"
their wounds. Anything you can do to encourage rapid
compartmentalization will surely help a tree.
When branches are removed, a tree forms callus tissue
over the opening and compartmentalizes the wound. The speed with
which a wound is compartmentalized often indicates the vigor of the
tree. Below is a photo of callus tissue forming on the trunk
of an oak tree where a branch was removed during a previous year.
Correct pruning technique left the branch collar
on this Pin Oak tree
Callus tissue walling-off the area
where a branch was removed
or trunk Flair
It's desirable to see
good buttressing (flaring-out) all the way around the base of a tree
trunk. However, when you see a flat side on a tree trunk at the base
of the tree, you should suspect a girdling root. Girdling roots grow
across the side of the trunk instead of growing outward, and away
from the tree trunk.
Usually, the leaves are smaller on the side of
the tree with the offending root. It's often necessary to remove the
root, by carefully excavating the soil around the trunk, and cutting
it out. Root cuts, unlike branch cuts, should be painted or sealed
with tree paint. Maple trees are the most common suspects when it
comes girdling roots.
Good buttressing, or root flair, at an Oak's base
Girdling root across the trunk of a Maple tree
In the event a tree
trunk is damaged by heavy equipment, it's best to cut loose bark
away, back to where it is solidly connected to the tree trunk. The
old recommendation was to shape the surgical cut into the shape of a
canoe (with pointed tips aimed up and down the trunk) but current
recommendations indicate that a circular shaped area is just as
good. Following surgery, exposed bark tissue around the edges should
be painted with orange shellac. The large area of trunk in the
middle (heartwood) should be left unpainted.
Below we see the desired response to a surgically repaired bark
area, with callus tissue beginning to grow over the trunk wound.
Eventually, this tree will compartmentalize the wound, even though
it could take as long as ten years.
This wound is showing good response to bark surgery,
with healthy callus growth on the edges of the wound
Conks are usually
hard shelf-like fruiting bodies (of a Fungus) which grow on tree trunks.
They should serve as
'red flags' indicating that something more may be
wrong with the tree. These areas can extend well beyond the spot where you actually see the
The fungus could
actually extend throughout much of the tree trunk serving to weaken the trunk.
Conks are Red Flags since they
a problem which may
on Tree trunks