Mechanics of heavy bending and idea for technique in junipers

Horticulture
1

Hi!

For severe bends on thick branches/trunks in pines the wedge cut makes a lot of sense. Reducing the diameter by 50 % reduces the bending resistance (stiffness) by more than 90 % (bending stiffness, or second moment of area is calculated with diameter in the fourth power for circular profiles).

However, I have several collected junipers with thick and short branches that is impossible to bend to the extent I desire. My understanding from Ryan is that, in particular old junipers are not able to redirect its resources radially as well as e.g. pines (due to heartwood?) so wedge cuts are not an option.

So my plan is to make an axially (longitudinal) split in the branch from start of the bend all the way to the end of the branch. Similar to splitting off deadwood before bending. Then you end up having roughly the bending stiffness of “two branches” half the diameter, resulting in a total stiffness of only ~12,5% of the unsplit branch. The reason is that you remove the shear resistance in the neutral axis (mid axis) of the branch which would allow the two split sides of the branch to slide relative to each other axially (due to the compressive and tensional stresses) when bending.

To make the tree able to repair it self I would bend “both branches” together using only a guy wire at the end of the branch so the cambium layers dont rub hard on each other during the bend. When bend is close to completed I would wrap the two branches tight in raffia so that the cambium makes contact and hopefully heal together. Applying heavy gauge wire after this initial bend could also help redirect and increase the bend even further.

If this works out then, in theory at least, it would also be possible to split a branch in 3 or even 4 splits, giving a 96 % or 98% reduction in bending stiffness. Where I can see a problem is if e.g. a secondary branch is on the opposite side of the trunk where the root that feeds that branch is. But in junipers, this might be possible to identify by the direction of the fishers in the bark and you can split accordingly.

The question is ;does anyone know if a juniper would tolerate this, and if so would cut paste between the two cambium layers be beneficial?

Best regards

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Trunk splitting is a technique used with Junipers.
Off the top of my head, I can not remember if you should raffia first or after the bend.
Have you searched the library for reference?
I would not split a branch more than once, probably to much damage to repair :-1:t2:
No cut paste need.

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Yeah, brach/trunk splitting in junipers is ok, rafia would go before bending, split-rafia-wire-bend.
Try to split it in the middle, cuz the thinner you split the harder it gets to keep it alive.
Doing more then one split pre branch would probably not be a good idea though.

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Thanks for your reply! I have seen Ryan use raffia before bending, but that is when splitting off deadwood, so you dont have the rubbing of the cambium you would want to heal together.

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