Air layering thick branches on a slant? (not perpendicular to branch?

[Rivka]

I know that many things with trees will behave quite differently if things are not parallel to the horizon. Upper facing shoots tend to get more energy from the tree, moistures pools on lower sides, leaves reach for sunlight, etc.
So in one way we need to keep many things level or risk the outcome being really lopsided, on the other hand, we can also use these phenomena to our advantage, tilting plants to direct growth.
So my question is if there is an issue with air layering on a slant? Can the bark removal be done in a non-perpendicular manner so that the final tree once cut off from its old trunk can be repotted at a tilt to align the new horizon? Also, this would have the effect of creating a wider oval nebari from an otherwise round trunk?

I have two scenarios I would love feedback on.
Scenario 1.
Horizontal to the ground, but at a slant (not perpendicular) to the branch. This would create a large oval cross-section and hopefully future nebari and keep the natural angle that the branch had been growing.


Scenario 2.
Slanted to both the horizon and the tree branch, giving you both an elongated Nebari and freedom to reorient the branch, as you rotate the cut back to horizontal during repotting.



I can see more advanced use scenarios for this when laying up thick trucks to be planed on steeply slanted surfaces as well.

So basically I wanted to check-in with those possessing experience that I completely lack.
Is this done? does it work? has it been shown not to work? If it does not work, can you explain the science surrounding the failure? is the results species-specific?

I completely understand the science as to why air layering works in general and in many ways #1 seems like a merger of air layering and the ground layering that happens as we make a "raft"

thanks for entertaining my "question everything" nature
-rivka

 

[Johnnyd]

I did an air layer on an angle successfully. The root mass grew on the lower side. No problem as long as the are sufficient roots to support the foliage. just re open the area with no roots and reapply rooting hormone the next year. The first example should not be an issue.
Osoyoung might be able to tell you the name of the auxin involved in gravity. It's in a separate thread (The Science of Air Layering).
Good luck!

 

[Rivka]

Osoyoung might be able to tell you the name of the auxin involved in gravity. It's in a separate thread (The Science of Air Layering).
Good luck!

that would be Gravitropism. and I was generally thinking it directed roots to grow downward, but was not sure if there were any signals telling a tree to grow roots from the lowest point available to it?

 

[BrianBay9]

I try to always keep my cut parallel to the ground. Obviously that will limit the locations for air layers in landscape trees, but for those on your bench you can tilt the whole plant to cut where you want and keep the cut parallel. As you say, if you have a obvious "down side", root will predominate there.

 

[rollwithak]

"Typically air-layered shoots form roots on the underside of the stem, which means that when subsequently planted out the tree does not have a radially orientating root system and so is prone to fall over as the tree gets bigger. To avoid this it is preferable to air layer vertical shoots, such as those formed after pollarding a tree. Alternatively, if a nonvertical branch is used, it can be potted and managed as a stockplant from which to regularly harvest cuttings for subsequent repropagation."

Air Layering - an overview | ScienceDirect Topics

www.sciencedirect.com

 

[Rivka]

"Typically air-layered shoots form roots on the underside of the stem, which means that when subsequently planted out the tree does not have a radially orientating root system and so is prone to fall over as the tree gets bigger. To avoid this it is preferable to air layer vertical shoots, such as those formed after pollarding a tree. Alternatively, if a nonvertical branch is used, it can be potted and managed as a stockplant from which to regularly harvest cuttings for subsequent repropagation."

yeah, good advice if the only goal is propagation which I assume was the case in the article. Bonsai is always pushing what nature lets us get away with to the bleeding edge and I guess this is no different.

 

[Rivka]

so follow up question? seems like Scenario 1 is relatively free of issues, so I will put that aside for now.

in scenario 2,
-is it pooling hormones on the lower edge that is triggering increased root activity at that location?
-is there anything in the initial setup or through the duration that can be done to help even root growth? (of course, slanting the tree so that the layer is horizontal rather than the tree itself being would, of course, be smart if it's possible.
-what are supportive measures that can be taken once the layer is removed and during or after repotting that would encourage grown to even out?
e.g. root trimming? re-girdle what had been the upper side to restart the process? (don't think you can do that to just half the circumference correct?), plan on re girdle the entire trunk a year or two later?


the thought that just hit me would be to do in 2 steps turn scenario 2 into scenario 1.
the first layering well below your final intended ground level, but still slanted and parallel to the angle you are hoping for in the long term. then a few years later, redo the process in what is now a ground horizontal position.

 

[Shibui]

It is OK to layer on an angle. In fact it is often preferable to avoid vertical trunks. Sure you may get a few less roots on the higher side but that can be rectified after the layer has been potted. May not even need to be as radical as another layer. Many trees will voluntarily produce roots around the trunk if given the chance and you can always rewound the area to help new roots get started.

 

[rollwithak]

so follow up question? seems like Scenario 1 is relatively free of issues, so I will put that aside for now.

in scenario 2,
-is it pooling hormones on the lower edge that is triggering increased root activity at that location?
-is there anything in the initial setup or through the duration that can be done to help even root growth? (of course, slanting the tree so that the layer is horizontal rather than the tree itself being would, of course, be smart if it's possible.
-what are supportive measures that can be taken once the layer is removed and during or after repotting that would encourage grown to even out?
e.g. root trimming? re-girdle what had been the upper side to restart the process? (don't think you can do that to just half the circumference correct?), plan on re girdle the entire trunk a year or two later?


the thought that just hit me would be to do in 2 steps turn scenario 2 into scenario 1.
the first layering well below your final intended ground level, but still slanted and parallel to the angle you are hoping for in the long term. then a few years later, redo the process in what is now a ground horizontal position.

View attachment 299200

Peter Chan recommends planting in sphagnum moss directly after cutting the air layer off. He swears by the stuff for these and sick plants in general.