opinion about heritage oak cabling

zoomfactor

Hi all,

I would like your opinion about cabling this ancient black oak in my back yard. It is 18' in circumference, 100' feet high, and has a 120' spread. Until 2 weeks ago, it was impeccably healthy. Then, a storm blew in from the north, and created a giant crack in the crotch, as I've drawn in the pictures below as a white line. It is spread far enough that you can see daylight between the sides of the crack.

The most respected arborist in town (Cortese Tree of Knoxville, TN) came in and pruned a bunch of limbs on the left side of the tree to reduce weight, then put four cables in roughly where I've shown with the black lines. They are pretty stout, I believe 3/8" diameter, and are attached to eyebolts connected to rods that go through the entire branch with a nut on the other side.

From what I read, this is a common fix for heritage trees such as this. My question is, will the limited flexibility of the limb movement created by the cabling system make the tree more prone to blow down? A friend of mine had his maple cabled up, and a year later it blew down. Also, will exposure of the crack to rainwater, fungus, and bacteria accelerate the failing structural integrity of the tree?

Thanks in advance!
Kim





This picture gives you an idea of the scale of the tree:


Another picture taken 90 degrees around from the crack:

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Eric Frei

Well, it's hard to tell from the pics as an over all 3D view isn't possible, however from my view those cables appear to be installed quite low meaning that above the attachment point of the cables there's still lots of length for movement. Also they pruned some weight off you mentioned.

This is a very hard question to answer from pictures, perhaps pictures from a distance of the entire tree and once again paint shop in the cables. Usually it is recommended that cables be 2/3 the way up the stems, that reduces a lot of movement in the remaining 1/3 of the stem above the cable.

This is the next big concern, yes that will start to decay over time, and with large old trees the slower growth will make it harder to grow sufficient reaction wood to compensate, plus the area is now more rigid from cabling meaning the tree isn't responding to movement so much. As trees get older you'll see their growth rings get smaller, trees grow a new shell every year however when they are that size it takes huge resources to cover the exterior with a new shell, and the surface area of that shell is getting larger every time.

Anything to try to stop decay like filling, expanding foam etc doesn't do much, fungicides can help but are toxic to trees, quite a difficult thing to stop. I would envisage over time that the crack will decay, the critical management concept here would be to ensure the tree stays healthy (mulch, soil conditioners, water etc). It would also perhaps be wise to slow down the growth of this guy and boost it's defences and root system, ask your arborist about a Cambitstat treatment.

Keep us posted on this tree, see if you can get some other pictures too.

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Sean Freeman

Hello there Kim,

Having visited his website and read his published articles I would be very surprised if Jim Cortese did not adhere to the BMP for cabling Bracing Guyinng and Propping (ANSI A300 Part3 2006).

Since you do not show the actual cabling in situ it is very hard to assess the relative height that the cables are set in the tree.

If you have concerns then you should contact him directly, based on his articles I would expect him to be only too willing to discuss your concerns and present some practical options if they are appropriate.

Generally it is sometimes appropriate in addition to the static cabling system to install a dynamic system higher in the tree to dampen any potential extreme stresses at the points of static attachment, but these are judgement calls best made by the Arborist carrying out the installation.

In terms of the crack now present in your tree you can really only attempt to improve and maintain the health and vigour of the tree through improving the soil and root environment, aiming for gradual long lasting improvements not sudden dramatic fluctuations....again Jim Cortese should be able to help you.

Depending on the wood decay fungi present in your area applications of antagonistic fungi such as Trichoderma sp may well have very positive impacts in both competing with and parasitising pathogenic fungi.

jim1nz

Good info here guys.

With regard to bracing, like everyone is saying, the tree should really be seen in order to get a more accurate gauge of whats going on.

Here we are using both static and dynamic bracing systems to maintain as much of the trees natural movement as possible. Its important not to completely remove the reaction growth from the tree as it becomes complete dependent on the brace. Braces should support and decrease the chance of failure but are NOT 100% guaranteed, the tree and brace should be checked and pruned/maintained when required.

To make it simple for you, i would probably use a 10 ton static wire rope and sling combination, which is non invasive cheep and easy to install. This is installed 1/3rd the way up from the split to the top of the tree. This is installed with not too much tension depending on how the tree feels.

I would also use 4 ton dynamic cobra 3/4 up from the split to the top of the tree.

If the union is not included or split, continue using the cobra dynamic system as opposed to the static system. This just supports the tree in case of storm or reduces the chance the limb hitting the target.

Here are 2 photos of a split oak we braced, both static and dynamic and a close up of the static system

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Eric Frei

Smaller scale fall arrest system video.

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zoomfactor

Thanks all for your replies! Jim1nz, that is one heck of a crack in that tree. Today I went outside and tried to capture a little better the nature of the problem in the big black oak. It is a bright sunny day here, so I had to mess with the contrast some - thus the weirdness of the colors. Here are some pics:

Overall view of tree. Red marking on trunk is where the crack ends.


Closeup of crack from the north side (same angle as previous picture).


Looking up at crack from the south side. I've drawn in one of the cables that comes into view. The vertical cable is for lightning rods.


Going back to the north side, this picture is looking up to show where the cables are. I've drawn them in exactly where they are located. Three wires connect the back fork of the left side of the tree, and the fourth wire, ties to the front fork of the left side of the tree. They all attach to the same branch on the right side of the tree. This is the most "straight-on" picture I could get, out of my second-story window.


Another angle looking up north side, taken from the 1st floor deck:


And another angle looking up to the top of the tree from the ground on the north side (ignore the telephone wire that runs across the picture):


I really appreciate your input! I am on a steep learning curve trying to get my head around this, so your comments are very helpful.

Thanks,
Kim

Eric Frei

Can you get a pic far enough away that we see the whole tree, then pen in the cables?

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zoomfactor

This is probably as far back as I can get:

Eric Frei

The attached PDF will also help.

Cabling appears to be half way or less between fault and branch ends, that will allow plenty of tip movement for wind.

BMP's state cables should be around 2/3 the way between fork and branch tip.

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Attached Files

Cabling_Tree.pdf (178.5 KB, 42 views)

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jim1nz

Great pictures Kim. It is hard to say yes or no when your talking about brace position. We have worked out that bracing is a good option and you can see a few system options.

Although the photos are good, the angles are really hard to decipher from any photograph unfortunately. We can give you an idea of position by the rules studies have taught us.

That crack is bad and needs urgent attention. Good on you for doing your homework and keeping both your and your trees best interests at heart!

I wish i could just do the work required for you, sure is a nice tree!

All the best