Can Codominant Stems At Base Split Sideways

S

Sandiegoutilityforester

Location
San Diego
Hi all,

This is my first post on this forum. I am a utility forester, and I come across a lot of eucalyptus trees that are codominate at base with included bark. I often wonder "can the tree split sideways?". As in, it seems natural that if the tree is going to split at the union, then one stem will go in the opposite direction of the other stem (let's call that direction 180 degrees). But can it split at an angle? Like 90 degrees or a diagonal 145? I know anything is possible, but how likely is it?

If you have seen this happen in tree failures that you have come across please share! Thank you. I have picture an example of the tree that prompted me to finally seek out more advice on here20200430_082428.jpg20200430_082428.jpg20200430_082722.jpg
 
In my experience, a tree like that will almost assuredly split and the trunks fall opposite directions, in the directions they are leaning. I suppose it is possible for them to fall somewhere else, but without a really strong wind or some other outside force to push them over, I would not expect them to do so. I’ve never seen it happen in my years in this industry.
 
In my experience and with the trees around me, usually when two stems are together like that all the limbs are totally one-sided and the stems look almost like mirror images of each other. The lean and limb weight are usually so overwhelmingly to that one direction it seems almost impossible for it to fall any other way.
 
Welcome! Always good to have new people

In my 45 year career I’ve never seen a codom tree like that have root failure to the side

In wind storms I’ve seen them fail. There are no anchoring roots in the ‘included’ radial area. When I yanked out smaller trees or shrubs like that the root systems were symmetrical and 180*

If there were root or trunk damage they might fail in some other direction though. Not saying anything you don’t know I’m sure
 
I've only seen one, with a ton of rot in one of the trunks, snap off like it had been cut through. But, it broke off right in the middle of the area with extensive rot. In amongst the crumbly wood was a 1/2" diameter piece of threaded rod that had been bent to form a loop on one end and still had a nut and several washers on it. I assume it had held a clothesline or a dog chain or something similar at one time. It was rusted nearly all the way through in places and I don't think it had been used in a couple of decades.

I think without such damage, the split will nearly always just follow the grain down to a root flare, and not cut across the grain to the outside of a stem above grade.
 
Tom Dunlap said:
Welcome! Always good to have new people

In my 45 year career I’ve never seen a codom tree like that have root failure to the side

In wind storms I’ve seen them fail. There are no anchoring roots in the ‘included’ radial area. When I yanked out smaller trees or shrubs like that the root systems were symmetrical and 180*

If there were root or trunk damage they might fail in some other direction though. Not saying anything you don’t know I’m sure
Click to expand...

Thank you all for your responses! That's a good point on root or trunk damage raising the possibility of an "unnatural" direction of split. I will consider all of this is my inspections to come.
 
Look closely in the canopy for crossing or rubbing branches, which may constitute a "natural brace".

Dr. Duncan Slater has put forth some very interesting and eye-opening research, showing that a crossing or rubbing branch in the canopy, limiting canopy movement can precipitate formation of a bark inclusion in the trunk beneath.

Sudden removal of a crossing or rubbing branch can suddenly expose the tree to loads to which it has not adapted, which can result in increased risk of failure of one or both leads. With one lead gone, the remainder is of course subject to loads for which it's not adapted either.

As I said, his work is thought-provoking and definitely worth taking a look at. At a minimum, it explodes the common pruning specification to "remove dead, diseased, crossing and rubbing branches".
 
I've cabled quite a few codominate eucs just like that here in San Diego county to prevent them splitting.

EHS steel cable n throughbolt hardware of course.

None of that dynamic cobra synthetic crap......

Jemco
 
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