Tilia cordata Brace and Cable

I think threaded rod at the crotch is more intended to moderate shearing movements at the crotch, not so much separating movement; that's what the cable is for. So, decay under the washer is not as much of a concern down there as it is for any eye bolts holding cable up high. But any decay at the base is a concern for obvious reasons.
 
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I have a few comments on the original job.
First, the eye bolts or lags are not welded or forged closed and look like some cheap hardware store bolts. Were they rated?

[/ QUOTE ] Be honest Mike. Do they need to be. That's a problem in our industry. The material all is rated but I've never seen a rated crotch. Not even in the top of the tree were I put my FS anchor point (that should ideally be rated)
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The second thing I noticed, and it is subtle, but you could have stacked alternating washers and nuts on the end of the brace rods. We can assume that all the wood under the washer will eventually rot away, especially with a basswood and low on the trunk, and then there's nothing left holding the rod. Creating something for the new wood on the end of the rod to grow onto gives the tree something outside the CODIT walls to support the rods over time.

[/ QUOTE ]That's a very good one. Knowing that in Tilia eventually all the interior will rot away until Codit wall four (the newly formed and Tilia's best barrier) If there are alternated washers the metalworks stay in place.

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Lastly, and this is a can of worms, but doing a crown reduction is a stress on a tree. Removing 15% of the crown should not make the difference between the newly cabled tree standing or falling. It will slow the growth of the tree, which is counter-intuitive, to me anyway. Don't we want to add new wood at a fast rate to overcome the advancing decay?

[/ QUOTE ] True, and that's IMO one of the most tricky parts of our job. But keep in mind that the trees growth doesn't slow down when reducing the crown 15%. The tree will instantly grow new (water)shoots to compensate our 'mutilating' work. What you have done is reducing the trees stress on the weaker parts. And there is the problem you stated. The forces on the wood are less so there will be formed less functional wood to keep the tree 'safe'

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Perhaps some fertilizer would be better.

[/ QUOTE ] NO.
Fertilizers make a tree grow... The growth (cell based) is formed by making longer and wider cells. The cells DON'T get any better in the way of strength. All chemically fertilized products are weaker (I mean strength and quality of the functional wood) than the non fertilized. Fertilize a structural weak stick and it starts to grow longer shoots and bigger leaves without strengthening it self in the proper way. The wind force will blow the crown apart sooner than a non chemically fertilized structural weak stick.
 
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I think threaded rod at the crotch is more intended to moderate shearing movements at the crotch, not so much separating movement; that's what the cable is for. So, decay under the washer is not as much of a concern down there as it is for any eye bolts holding cable up high. But any decay at the base is a concern for obvious reasons.

[/ QUOTE ] The idea of the brace rods is to isolate the crotch from movement, and create compression between the two halves. The only way grafting of the two halves can happen is through compression.
Ultimately we want the two halves to grow together.
I don't know how many of you remember the writings of Bob Wulcowitz from the old ISA Web board, but he was working on using small surgical tools to slightly injure the tree on both sides of the split. The resulting thin barked, undifferentiated, un-lignified wood more easily grafted together. The theory being these small connections would grow bigger and eventually be continuous.
The first thing we need is absolutely no movement between the halves, which is only possible with brace rods.
The wood under the washers is compressed, no new wood will form under them. This explains why countersinking has no value other than to staighten the orentation between the washer and the rod, which could be also done with a metal shim between the washer and nut.
How much rod, with stacked alternating washer/nut, you leave sticking out of the tree, will determine how many years of support the rod will give.
Just know that the wood under the first washer will be inside the CODIT walls.
 
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Be honest Mike. Do they need to be? (rated)

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It is wise to follow the ANSI standards; doing so will give you tremendous protection from liability.

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But keep in mind that the trees growth doesn't slow down when reducing the crown 15%. The tree will instantly grow new (water)shoots to compensate our 'mutilating' work.

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We know from topping research that overall growth is increased, but the growth increase takes place where the cutting is done. This re-growth uses energy that would, in part, be used to add new wood. It also leaves the tree's energy reserves very low.
If one looks at the growth rings on the end grain of a log, he can see big and small rings and can correlate them to stress factors, like foliage removal.

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All chemically fertilized products are weaker (I mean strength and quality of the functional wood) than the non-fertilized.

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Then perhaps we should artificially create a low level of fertilizer.
How about adding compost and a large chip bed, doing a soil test and adding only deficient minerals and nutrients, watering during dry times, adding Mychorizal fungi and beneficial bacteria, soil injecting Merit?
 
Using hardware store eyescrews/bolts is not a good idea. they're made from mild steel and are much more likely to bend open under very low tree loads. For smaller limbs I guess welding the bent eye might work...but I wouldn't do that. Using threaded rod and eye nuts is much easier and cheaper.

countersinking washers is not a good idea. All that does is make a larger wound. We all know what happens when a tree has a large wound.

When I use through bolts for bracing or cabling I use a double washer setup on the ends. Here's what you'd see...tree-washer-nut-washer-nut. The reason is that there will always be a decay pocket behind the first washer because of the through bolt. As time goes along the decay grows and the tree puts on more growth that will eventually envelop the first washer. But, that washer is set on decayed/weaker wood. As time continuess the tree will envelop the second washer. Now there's a layer of solid wood with no decay between the washers. This will be a much stronger anchor after some time.

For anyone who doubts this...think about the times that you've cut voluneer trees out of chain link fences. the trees have grown and enveloped the tree but not girdled because the point-contact is not circumferential and constant. Just this morning I walked up to the coffee shop and saw some 5" dia trees in a chain link fence that are thriving.

When I've had splilt trunks I've installed through bolts to add physical support. Otherwise I would be afraid that the trunk would continue to 'zipper' and fail more. Buy trying to 'freeze-frame' the trunk there is the possibility of Wulkie's idea working. If the two edges move there is no chance that a new cambial sheet will develop.
 
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Removing 15% of the crown should not make the difference between the newly cabled tree standing or falling. It will slow the growth of the tree, which is counter-intuitive, to me anyway.

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It seems almost counter-intuition to NOT reduce endweight and do crown reduction before cabling. The goal is to loosen the weight exerted on the union. Even a 10% crown reduction is a LOT of weight taken off the limbs. Obviously you have to be extremely cautious with senescent trees.

I don't think that thinning slows the rate of growth. In california we cable a lot of large oak trees and ALWAYS thinned and reduced-end weight before installing cables.


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Don't we want to add new wood at a fast rate to overcome the advancing decay? Perhaps some fertilizer would be better.

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Root-to-shoot ratio. It seems there is a common misconception about the use of fertilizer and tree growth. When fertilizer is used you are sacrificing shoot growth at the expense of root growth, altering the ratio between the two and in the end, often times, doing more harm than good to the overall health of the tree. Now mulching might be a much better idea. And that's not to say that there aren't valid times to use fertilizer, but in this case it doesn't seem appropriate.

Lastly, the technique of using multiple washers/nuts, is that in the standards for cabling, or have there been tests to show the difference in strength between the two methods??


jp
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Lastly, the technique of using multiple washers/nuts, is that in the standards for cabling, or have there been tests to show the difference in strength between the two methods??


jp
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It doesn't have to be a standard. Not all the bracing situations call for it. Trees that are more in need of the method are Tilia, Acer, Aesculus and Liriodendron.

It's not the difference in strength JP, It's the difference in grip. The multiple washer method is to make sure that in case of decay of the total inner trunk, the washers still secure the metalworks in the healthy newly formed wood.
 
It's not the difference in strength JP, It's the difference in grip. The multiple washer method is to make sure that in case of decay of the total inner trunk, the washers still secure the metalworks in the healthy newly formed wood.

That's right...think of how much more grip a screw has rather than a nail. Not the best metaphor but it works...

Certainly using two washers would never be in violation of the A300 standard.
 
What I don't understand is if the main objective is to not allow the crotch to have any movement then why wouldn't you countersink? Instead of thinking about a young Tilia sp. that has thin bark and soft wood that will contour the shape of the washer anyways, maybe a hard wood with thick deep fissured bark. The bark will naturally slough off or decay, which will lead to some movement. As soon as movement occurs barrier zone will be constantly damaged allowing the decay to travel out farther.

As far as countersinking creating a larger wound, I will agree it does, but only slightly. Many pruning cuts make a slightly larger wound than the limb itself (ie. a 2" limb may leave a wound slightly larger than 2"), the key to the cut is the placement of the cut and not solely on minimizing the size. This is done to ensure comparmentalization occurs as quickly as possible. If countersinking does speed up the compartmentalization process then why wouldn't we?
 
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It seems almost counter-intuition to NOT reduce endweight and do crown reduction before cabling. The goal is to loosen the weight exerted on the union. Even a 10% crown reduction is a LOT of weight taken off the limbs. Obviously you have to be extremely cautious with senescent trees.

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I'd guess our difference in perspective might come from our different locations. My most robust tree would probably be a removal, based on it's failure to grow and low vigor, to you.
Our growing season is about 5 months a year, and two of the months it so hot and dry, the trees are shut down anyway. Sound a little different than your tropical paradise?
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...altering the (root to shoot) ratio between the two and in the end, often times, doing more harm than good to the overall health of the tree.

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It's funny how many arborist see roots as so important, and yet don't feel the least bit concerned about wacking 10 or 15% off the upper half of a tree.
The reason being, when you kill roots, you can see the top lose vigor or die back. When you kill the top, you can't see the roots lose vigor or die back, but they do.

A tree will always find a balance of roots and shoots, in time. One can't survive without the other.

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I don't think that thinning slows the rate of growth.

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Removing one functioning leaf slows the rate of growth.
 
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I'd guess our difference in perspective might come from our different locations. My most robust tree would probably be a removal, based on it's failure to grow and low vigor, to you.
Our growing season is about 5 months a year, and two of the months it so hot and dry, the trees are shut down anyway. Sound a little different than your tropical paradise?
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True, often times in hawaii it seems the line between arboriculture and vegetation management becomes a bit blurry
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jp
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I think there are two other considerations in deciding whether to crown reduce, and they work together 1) Are you cabling with steel, and 2)are you in an area with either heavy winds or heavy snow during the time leaves are on the tree. If both, then crown reduction is usually called for, IMO. Otherwise, the rigid element you are introducing usually causes massive storm damage out beyond the cable. You end up with many 3,4,5", and bigger de-facto "drop crotch" cuts, instead of 1,2" ones done purposely.

This is expecially true for Silver Maple, Cottonwood, Siberian Elm, Green Ash: IOW, all the crappy species that dominate the landscape our here. These trees usually need light crown reduction, even when not cabling, due to our weather extremes. By light, I'm talking about pole pruner cuts, for the most part, and small hand saw cuts, adjusted according to the length and taper of each leader or branch. (The term "crown reduction" is sometimes abused to justify what really constitutes topping).

Mike: If reduction cuts are small, made during winter, and little or no other live growth removed, I think reduction in wood growth that season will be marginal, especially compared to what would happen with massive storm damage down the line. There needs to be lots more research on this and on decay due to drop-crotching.
 
The turning moment for not countersinking came from Bartlett research that was presented at the ISA Conference in Salt Lake City. The article was published in the Journal at about that time. The research showed how much larger the decay was in countersunk trees. If I remember correctly they did tests that countersunk just the bark and also countersunk to a surface that was perpendicular to the threaded rod so that the nut had the best load bearing surface.

If a perpendicular load is desired it is pretty simple to cut some short pieces of water pipe at a salami angle. then put this bushing between the washer and nut.

On trees with really thick, corky bark I shave away some in order to set the washer on more solid wood.
 
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