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12th February 2007, 10:59 PM
| #1 | |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist  Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
|  V and U shaped Crotch Strengths, included bark| codominant stems etc
This is exceptional stuff with some great data. How strong are these unions and what you can do about making them better. I wonder how many of us can actually tell the difference between an included bark and non included bark union? The data shows that a non included bark union isn't that much stronger anyway. Also, when the diameter of the branch is less than 2/3's the trunk dia the strength is better. I encourage all to read from page 50 onwards on the second PDF about types of crotches and failures. codominantstemsincludedvsnot.pdf crotch strength PDF 4.4mb Also from Gilman's PDF attached ... Quote:
    
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18th February 2007, 03:27 PM
| #2 |
| Sappling  Join Date: Feb 2007 Location: Longmont, CO
Posts: 16
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Thanks for finding this information Eric. I'm going to use this with my customers to show them why I say included bark is bad.
__________________ "Quality costs as much as it saves." My great uncle Simon Murphy |
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18th February 2007, 10:56 PM
| #3 |
| I'm new here so be nice  Join Date: Feb 2007 Location: Austin,TX.
Posts: 2
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Good stuff! Thanks for the links!
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23rd February 2007, 06:13 PM
| #4 |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
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Found these two pics of a typical type of failure.  
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24th February 2007, 07:28 PM
| #5 |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
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Actually your last pic, looked like that one had no included bark but couldn't see the other side ... ... I once heard if the branch bark ridge is pointing outward like a small mound then it's likely not an included bark union, if it's inward then it is. But the ole elephant ears on advanced cases is a dead give away. #8 below is definately included whilst #13 maybe not
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2nd March 2007, 06:06 AM
| #6 |
| Semi-mature vigorous tree  Join Date: Mar 2007 Location: Urbana, IL,usa
Posts: 69
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I've noticed "u" shaped crotches eventually become "v" crotches! (Huh?) Yeah, as the stems increase in diameter over several years and they are growing in the same general direction, the "u" eventually closes and invaginates the branch bark ridge inward! Has anyone else seen this?
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3rd March 2007, 07:06 PM
| #7 |
| Mature Tree Join Date: Feb 2007 Location: Melbourne, Victoria, Australia.
Posts: 1,605
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Heres a classic co-dom failure. Tree was a Spotted Gum Corymbia maculata. Split right to the base. Looking at the stump i think it was doomed from day 1. Trev |
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3rd March 2007, 07:30 PM
| #8 |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
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Great pics, well and truly stuffed. Was that cabling for the dismantle mate?
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4th March 2007, 09:37 AM
| #9 |
| Mature Tree Join Date: Feb 2007 Location: Melbourne, Victoria, Australia.
Posts: 1,605
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Just tied up with rope after they first noticed the split untill tree could be removed. Kept in place while taking it apart.
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8th March 2007, 09:18 AM
| #10 |
| Semi-mature vigorous tree  Join Date: Jan 2007 Location: Austin TX
Posts: 102
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Great pictures. Very Clear showing the failure point. Thanks
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1st November 2007, 03:37 PM
| #11 |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
| Re: V and U shaped Crotch Strengths, included bark vs non included etc
Geee I'm getting some real kicks out of predicting stuff. The pic below was taken 12 Feb 2007 of a grey gum just down the road in the dog park. It's the same pic as in my first post.  Now on Sunday 28 October 2007 guess what? Yeah, it busted and stuffed a few other trees. So, was predictable.  
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1st November 2007, 09:07 PM
| #12 |
| Mature tree  Join Date: May 2007 Location: sydney
Posts: 422
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc
good prediction.... so what's next weeks lotto numbers???? |
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1st November 2007, 09:43 PM
| #13 |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc
Hey, I aint splitting the winnings with anyone! 
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3rd November 2007, 12:58 AM
| #14 | |
| Semi-mature vigorous tree  Join Date: Jul 2007 Location: CT USA
Posts: 182
|  Re: V and U shaped Crotch Strengths, included bark| codominant stems etc Quote:
I noticed as did ekka you had tied it together to keep it together while dismantling the tree. What was your procedure Trev on the removal? I dont think i would climb that. Did you have a bucket truck? Any more pics from the take down?  -Daryl
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8th October 2011, 05:33 PM
| #15 |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc
Had a storm this morning. Nothing too serious and we certainly had stronger winds a few weeks ago. The ideology that it hasn't failed before or that it withstood stronger winds prior so shouldn't fail is a falsehood. Co-dominant union with included bark on a Bribie Island Pine, no damage to roof or strong old fashioned gutter but a short journey to work for this one.       Now here is another tree, larger and more exposed. You can see the future eh.    
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8th October 2011, 06:32 PM
| #16 |
| Moderator - Previously known as JayD  Join Date: Feb 2007 Location: TreeWorld, Sydney Australia
Posts: 2,031
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc
As I travel around looking after trees I have noticed that trees with the V crotch union has potential for failure at any size, I found this specimen while I was walking for my fitness... Now this is not a big tree, it is approx 15 mtrs tall and DBH of 40 cm. I'm not sure what caused the tree to split as there is no signs of impact, so I concluded it split with high winds and poor structural form V crotch...also you can see by the woundwood formation it has been this way for at least a season.  I placed my hand saw into both sides of this tree to demonstrate the extent of the split...    This is a good representation of the type of V crotch failure I observe in my travels. When I have control, or input to this type of structural failure I will always recommend removal as these trees are only going to get bigger and it's a matter of time before they fail. imo With your last photo Eric, the clock is ticking...not good especially where it is located !
__________________  Member: Australian Tree Association Join the Australian Tree Association...Have your voice heard ! Arboriculture, A life long study for some, a passing phase for others © Jeffrey J Darby 2011 Last edited by Jeff Darby; 8th October 2011 at 06:45 PM. |
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8th October 2011, 08:16 PM
| #17 |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc
Cabling and bracing is an option. An evaluation has to be made, cost vs benefit. If it costs say $1500 to through bolt and cable and that provides 10 years of integrity, then would you consider that a deal and go for it? Or would you say cut it down and replace now? If the tree has good vitality and vigour, and the only concern is structural integrity that can be rectified, then why not cable and bolt? If the tree has poor vitality and vigour, and it is likely that regardless of structural integrity it will continue to decline and likely not live out 10 years then is cable and bolt viable? If the tree is immature and the defect will exacerbate in forthcoming growing years is it wiser to cull now and replace with a defect free specimen? So, as arborists we need to consider options, costs, benefits, longevity, safety etc.
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21st October 2011, 07:14 AM
| #18 | |
| Moderator - Previously known as JayD Join Date: Feb 2007 Location: TreeWorld, Sydney Australia
Posts: 2,031
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc Quote:
I agree with all of the above quote, however I feel as arborists we should be considering good form in trees for retention in public areas the V crotch union is known to be a bad form when it come to structural integrity so at the planting stage should we be rejecting saplings with this form...and try to not let the structual genetics in this form to propagate? Yes we can bolt, yes we can cable, but wouldn't it be better to plant good stock in the first place ? and doing so avoid a known form which could very well split at the union 10 years into your investment wasting or causing unessessary concern in the future ? something to ponder on..
__________________ Member: Australian Tree Association Join the Australian Tree Association...Have your voice heard ! Arboriculture, A life long study for some, a passing phase for others © Jeffrey J Darby 2011 | |
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21st October 2011, 05:56 PM
| #19 |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc
Good nursery stock is what we need but how many were nursery stock vs remnant existing trees? We have to deal with existing problems, provide management solutions. If you can get 10 years more out of a tree that size for $1500 then that is only $150 a year to maintain that canopy cover.... worth it frankly. But you could also replacement plant now and keep the tree too. That way in a few years time you will have a maturing decent replacement under way. The urban amenity tree is under great pressure and needs to be seen in the same light as forestry view their stock. Forestry plant, raise and harvest their trees .... the urban forest for most parts has to be planted, raised and trees managed to the point where they no longer are viable and culled. They're not there for ever (for most parts, sidewalks etc), they say 50 years is a decent innings for most trees. Now in large parks they can get a lot more out of trees, but still no tree's life is infinite. As was seen in those Treenet videos, trees need room to die as well especially if you want habitat creation and longevity. That tree you have shown, I would cable and bolt it. The trees here in the units, I have said the same but some people will ask, "how much to also cut it down" and the average punter gets the two prices, $1500 to bolt and cable and $1200 to remove.... guess what most people do? Yes, remove as they see the problem solved cheaper because they do not like the tree or see it's value/benefits. 
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22nd October 2011, 11:02 AM
| #20 |
| Moderator - Previously known as JayD Join Date: Feb 2007 Location: TreeWorld, Sydney Australia
Posts: 2,031
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc
The tree I have posted about in #21 is still standing today. I have reported this tree to the powers that be, so from my duty of care point of view my job is done. The powers that be have chosen to leave this tree as it is with no bolting or cabling. Which for us as Arborist probably is a good thing because now we can follow this young mature tree as it deals with high winds and storms in the future. When we have gusting winds I have been noting down wind speeds and occasionally I walk down to the tree and just watch the split open, close and twist in reaction to the gusting winds. As with any thing like this time holds the key, will the tree itself deal with this split or will nature deal out its final verdict ? I will keep you posted..
__________________ Member: Australian Tree Association Join the Australian Tree Association...Have your voice heard ! Arboriculture, A life long study for some, a passing phase for others © Jeffrey J Darby 2011 |
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22nd October 2011, 11:28 AM
| #21 | |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc Quote:
Far out though, for the sake of say a 1" galv threaded rod, two washers, 4 nuts plus some steel cable (use those Rigguy ends for the cable) why not shore up the tree? Put the through bolt above the fork, just as explained in this thread then the forces will act to press the stems together rather than split, the bolt acts like a pivot/fulcrum. The cable further up reduces the separation of the stems. You may argue that in bad weather no-one is around but why not secure the asset for the future rather than let it bust apart? It's funny how much money a council will spend on pruning, even injecting trees for diseases then look at how much they spend on bolting and cabling. Bugger all I bet. There's an old mindset that cabling trees is a no no, it's admission of a defect and if something happens down the track (cable busts, karate effect breakout etc) then liability is put back onto the tree owner or cabler. In essence the mindset is that cabling a tree is acknowledging a defect and in so doing exposes your liability. Utter nonsense. Cabling is mitigating a hazard, and if performed correctly like any other task it is a sound and viable option. If a micro burst hits the tree and destroys it then the argument is that regardless of the cable even a sound tree would have failed. Remember, the tree also has a bolt in it. You'd lightly tension the two tops, pulling them together then cable it. Once that is done then you'd drill and bolt above the V fork. In no time the tree will also occlude the hardware getting stronger. The other issue you have to consider is decay between the two stems as a crack is already there, but that looks like a red gum and they are tough guys for decay, with a shored up canopy I wonder if decay could even expand as far as Mattheck's 70% rule. 
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27th November 2011, 01:01 PM
| #22 |
| Moderator - Previously known as JayD Join Date: Feb 2007 Location: TreeWorld, Sydney Australia
Posts: 2,031
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc
Today I revisited our tree with the split V union as it is windy in Seven Hills, This tree has nothing done to it to help cope and to me, it seems to have gotten worse, I rigged up a devise for measuring the extent movement in the split union and here is a small video off my phone for you all to have a look at. Note now you can see daylight through the split trunk... here are wind speeds for Seven Hills today...  I feel as nothing has been done to help this tree that it is only a matter of time for the right conditions to split it in half and wasting years of growth, bolting or cabling would help this tree deal with the problem as Eric has suggested but it seems to be left to fend for itself...
__________________ Member: Australian Tree Association Join the Australian Tree Association...Have your voice heard ! Arboriculture, A life long study for some, a passing phase for others © Jeffrey J Darby 2011 Last edited by Jeff Darby; 28th November 2011 at 04:33 PM. |
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27th November 2011, 02:32 PM
| #23 |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc
Gee, and I thought Sydney was inundated with experts in council, clearly not with the management of this tree.  
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26th January 2012, 05:42 PM
| #24 |
| Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane
Posts: 12,820
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc
Here's a little ripper I drove past today, was going around the round-a-bout and spotted it, saw daylight between the stems!  Location is northern side just inside wooden fence Stanmore road and Sandy Creek Road Yatala round-a-bout Here's the pics.   
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26th January 2012, 06:09 PM
| #25 |
| Moderator - Previously known as JayD Join Date: Feb 2007 Location: TreeWorld, Sydney Australia
Posts: 2,031
| Re: V and U shaped Crotch Strengths, included bark| codominant stems etc
Good find especially when you think you were driving... the tree is bad nick structurally and biologically that split has been there a few seasons...
__________________ Member: Australian Tree Association Join the Australian Tree Association...Have your voice heard ! Arboriculture, A life long study for some, a passing phase for others © Jeffrey J Darby 2011 |
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