Question of the Week Number 2: November 29, 2018

“We just bought a new home where the live oak trees look like wires are going to kill them. Is there anything that we can do to save them?”

The original intention of supporting new trees was good, but unfortunately they forgot to come back and remove the wires once the trees were soundly rooted. Now the trunks have grown large enough that they are being girdled by the tight wires.

Wires that were used to keep tree bolt-upright until it rooted tightly into the ground have overstayed their welcome and should have been removed two or more years ago.

What happens in this process is that the interior wood of the tree expands around the wire until it essentially cuts through the outer tissues. The bark is cut, then the critical phloem is as well. That’s the cylindrical tissue that carries sugars manufactured by the leaves in the process of photosynthesis down to the roots. So their supply line is severed.

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As the phloem is lost, so is the layer just inside it called the cambium. It’s the cambium layer that divides to give rise to new phloem to its outside and xylem to its inside. Xylem makes up the “wood” of a tree’s trunk, so it’s important in the strength of the trunk and in supporting the branches and leaves. The xylem is also the conduit through which water and nutrients are pulled from the roots up to the leaves.

Just inside the bark there is a layer of conducting tissues (phloem) that transports sugars from the leaves down to the roots. When the trunk is girdled, those sugars accumulate just above the area of damage, resulting in swollen tissue due to the backup of sugars. You can see that in this photograph.

All of that damage is done just by leaving the cable in place a year or two longer than necessary. It can also be done much more quickly by careless use of a line trimmer, also by leaving a dog chain tied around the trunk of a tree.

Back to your original question of whether there is anything you can do to save trees that look like this? Perhaps, but they are going to be severely weakened. You probably ought to have a certified arborist work on them. It may be that the cable can be removed. If not, or if the damage is quite severe, you may have to cut the tree below the girdled area and allow new top growth to develop from beneath.

However you remedy the situation, however, my bet is that you’ll not make the same mistake that the former homeowner did.

Good luck with your trees!

Posted by Neil Sperry
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