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My Blog
My Blog
Blog
Tree Cavities
| Posted on August 12, 2016 at 2:04 PM |
comments (10)
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In this blog post, I’m
going to put my arborist hat on again.
I’m going to discuss something that I’m sure just about everyone has
seen; a large hole in a tree. Sometimes
it is call a hollow. In arborist
language, we refer to these as a cavity.
In many cases, these are a result of some sort of damage, whether that
damage is from lightning or high winds or animals. Many times, trees in an urban or suburban
setting may have a cavity or a wound due to something caused by people. These injuries are usually inadvertent. Someone strikes a tree with an automobile,
construction equipment or a lawn mower.
It could also be as a result of improper pruning. Trunk wounds that
penetrate the bark will damage the cambium layer, a thin layer of vascular
tissue, which is vital to movement of water and nutrients. If less than 25% of the bark around the trunk
has been damaged, the tree will probably recover. When fresh wounds occur on the trunk, the damaged
bark should be removed carefully, leaving healthy bark that is sound and tight
to the wood. A wound dressing (tree
paint) is not necessary. Sometimes I do
use a spray “pruning tar” when I prune away larger branches. Theoretically, it seals the area where the
branch was removed. For wounds, you will be
able to observe the wound closing from the edges each year as the tree grows. When an older wound is discovered, remove the
dried and loose bark back to the area where the new wood can be seen along the
edges of the wound. Trunk wounds that
are not addressed could potentially be a hazard in the future. Once a wound occurs,
decay-causing fungi can enter the heartwood and the decay process begins. Trees have a unique defense. The wood around the injury begins to produce
special compounds in the wood cells that set up a wall or barrier to isolate
the infected area. This is called compartmentalization. In a vigorous tree, new growth continues to
form and add to the sound wood. Once
compartmentalized, discoloration and decay will spread no further unless one of
the barriers is broken. Storm-damaged
branches should be properly pruned to expedite the healing process. Avoid pruning directly against the trunk since
flush cuts can lead to extensive decay. Remember
to prune away from the branch collar, as I said in an earlier post. (“Tree Care
for Turfgrass Warriors”) Prune hazardous
branches immediately. Years ago, filling
cavities was an accepted practice. The
wound would be cleaned and scraped down to sound wood and filled with cement,
mortar, or bricks. These practices
frequently penetrated the tree’s natural defensive barrier, allowing decay to
spread. Fortunately, this practice has
decreased, along with flush cuts and tree wound paints. If the tree ever had to be removed, having
cement or bricks in a tree could be very dangerous for the arborist crew. Your mission is to help the tree heal
those cavities/wounds. If we can't get
them to heal, we can try to get the tree to compartmentalize those cavities. The cavity in itself is not important
unless it is a very large one (like half the diameter, or more, of the tree),
but it is the breeding place which it affords for enemies such as insects and
fungi that is highly important and worthy of the most serious consideration in
the care of trees. The accumulation of moisture and the
exclusion of light, which are characteristic of every cavity, are the ideal
conditions which the spore of a fungus disease seeks. You want to make sure this does not become a
major health issue for the tree so it doesn't become weak, then come down on
your house, automobile or loved ones in a storm. Having cavities near the base is worse
than having one up high. If decay sets
it in at the base, the tree could become unstable. Here are some courses of action: 1.
You want to keep critters and other stuff out of that hollow area in
that tree, get some screen material (metal or plastic screen is fine - like the
material from a screen door or porch).
Cut it to size for the entire area.
Tack it up around the area. Use
short nails (like tacks, not thumb tacks, but those might work). Do not use long nails that will penetrate
through the bark into the cambium. A
screen will allow air flow. 2.
Do not spray more water into the openings to try to clean it. You want this area to get as dry as
possible. 3.
Using your air hose attached to an air compressor to clear it out is
fine. 4.
Try to clean out or pull away any loose material. But don't pull away any
"good/healthy" bark or wood.
Cut off any ragged bark edges with a sharp knife or saw. You could even use a hammer and chisel. If you can take the surface down to healthy
material, that's fine. Take care not to
remove any healthy bark and expose more live tissue than necessary. If possible, the wound should be shaped like
an elongated oval, with the long axis running vertically along the trunk or
limb. All bark around the wound should
be tight. 5.
If you are feeling really industrious, get some lime sulfur solution and
spray it (lightly, with a pump sprayer, not something attached to your garden
hose or a hose attachment) all over the inside of the cavity - after you
manually clean it out. Lime sulfur is
very caustic. It can mess you up. Wear protective clothing, a mask and eye
protection. Lime sulfur also may be hard
to find. Or, use copper fungicide. Same procedure. Copper fungicide can be found at Home Depot
or Lowe's. Do this, then install the
screen. 6.
As I said, in the old days (actually not too long ago), they used to
fill tree cavities with concrete. They
thought it would strengthen the tree. It
is now known that it causes more injury. 7.
Once you have treated the cavity, and have covered it with the screen
for a while, some say you can fill the hollow with spray insulation. Not sure about that. I think that could possibly still retain
moisture, or trap moisture behind it.
The point is to get that cavity clean and as dry as possible. The screen allows for airflow and keeps out
any animals. 8.
This tree needs TLC now. It is
under stress. Make this tree the top
priority for tree trimming/pruning. Get
rid of the deadwood up top. If possible,
or if there is a bed around the tree already, get some good mulch around it. 9.
If there are insects in the vicinity, it is okay to spray insect killer/pesticide
around that area. Just on the surface of
the soil. Do not get it on the tree. 10.
This tree will need SLOW watering if you get in a bad drought at some
point. 11.
Also think about fertilizing the tree.
Having a professional arborist fertilize it would be great. If you can’t go with a professional, do it
yourself. Fertilizer stakes are
okay. Getting a root feeder and using
that with your garden hose would be even better. Remember to fertilize out along the drip edge. Below is a photo of a tree in my
yard. I’ve done what I could. The screen material I used is something used
to cover a gutter on a house. It was
attached with some very small and shallow screws which did not penetrate the
bark. The bad news is, this cavity is
right at ground level, at the base. Is
does get wet. But, the screen allows it
to dry out well. Guess we’ll have to see
how this works. Seems okay for now.  |