Maple airlayer turning brown

Cuzza

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Hi team, around the start of spring (September 15th) I began my first ever airlayer. My Sangu Kaku is a multi leader and a great opportunity for multiple projects.
Contrary to my own doubts it has managed to spout roots and leafed out amazingly. Everything was going great, I noticed so solid roots in the bag.. and then I noticed the whole top layered half has gone brown and a dry.. it's coming into summer now and I don't know if it's just sunburnt because it gets pretty hot here, or if it's because the roots tried out?? The bottom half is going great still with heaps of new growth and no leaf defects..

The trunk below the layer to the lowest branch is dying back and going black.

Do I need to separate the layer now into a container? Or defoliate the top leaves? Or both?
Obviously the top half is large and was planning on reducing that quite a bit as I remove the layer anyway..
Our summer goes quite late but I'm unsure as to if the timing now means there's another growth window for the new roots to develop or if I will even have enough new roots yet to remove

I don't want to lose the layer so advise is very very welcome.
 

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cbroad

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From talking to other people and from personal experience, Sangu kakus can be hard to air layer. In my case, the top girdled section almost immediately turned brown and failed, I think within a few days...

Hopefully since yours made it far enough to throw roots, it will make it. Even if every leaf drops, there might be enough stored energy to flush again.

Discoloration of the foliage is normal for air layers, every one I've tried (across different genera including Acer) and succeeded with has had that happen. I think I read here somewhere that it had to do with ethylene gas?

As for the blackening trunk, mine did the same thing below the girdle and eventually stopped right above a significant branch. This has to do with a CODIT response from the tree, which means the tree is compartmentalizing the damage/death of tissue which is a good thing.

Search "CODIT response" here on the forum. I learned about it from @0soyoung, he has a wealth of knowledge about plant physiology and will definitely be able to explain what's happening to your layer much better than I could.

Maybe all you may have to do is prune it back some to alleviate the stress on the foliage but I would wait to make the next move with it until you hear some actual advice.

Good luck!
 
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coh

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Hi team, around the start of spring (September 15th).. and then I noticed the whole top layered half has gone brown and a dry.. it's coming into summer now and I don't know if it's just sunburnt because it gets pretty hot here, or if it's because the roots tried out?? The bottom half is going great still with heaps of new growth and no leaf defects..

Are you saying that all of the leaves on the part above the layer have died? Hard to tell from the photo. That's a bad sign if so, I don't think I've ever had a layer "work" when that happened.

How do the roots look in the layer bag? Is the trunk above the layer still green under the bark?

PS, I have successfully layered a Sango Kaku though I think it took longer than normal before I could separate the layer.
 

0soyoung

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I too am somewhat confused about the current status of this, but it is an all-to-familiar a story to me. The bottom line is that even if only some leaves on the layer have withered, turned brown and are still hanging on, there is no hope for the layer.

If you were watching daily. @Cuzza, you would have seen this withering & browning move progressively up the branch being layered. As disappointing as it is, I am still a fascinated watching this, when it happens. On the plus side of these catastrophes, I learned more about basic tree physiology from them than just about anything else I've done.

Auxin is produced by branch tips, buds (new branch tips located at nodes), and leaves. Some gets loaded into the phloem (inner bark) along with carbohydrates from photosynthesis, but it is biologically inactive. The biologically active auxin is handed off from one cambium cell to the next by some special proteins (PIN). As a consequence, this biologically active auxin moves in only one direction, toward the roots, by a process that is known as Polar Auxin Transport (PAT).

In a sense, PAT serves as a signal that there is life above. When we prune or girdle a branch, we disrupt PAT to the cambium cells at the top of the cut or bottom of the girdle. The cambium doesn't die immediately because some can be unloaded from the phloem. Stuff in the phloem can go up or down, equally, but to go up it must overcome gravity. It can, because the phloem is pressurized by the cells in the leaves that actively load carbohydrates and auxin into the phloem tubes. So the cambium continues to live until the topmost cells can no longer off load enough auxin. Then they die and the next in line following the direction of the PAT stream. As this happens, the bark on acer palmatums turns to dark brown or black. The blackening will usually stop at the next node below because nodes have auxin sources = buds (though they may not be visible).

I think you can see this from this photograph. Dry withered leaves still clinging to the layered branch can be seen in the lower right corner. Moving left (which is downward, toward the roots of the mother tree), the green stem of the layer, the few roots that had formed, the girdle. and the blackening stem below (in the sense of PAT). The blackening has extended downward, almost to the node below which has a thin live branch. Given a little more time, the blackening would have stopped at this node.

2012-09-16 14.36.06.jpg

If the stem had been pruned at the same point instead of it being girdled, exactly the same thing happens to the bark of the 'stub'.

I find a discoloration in the wood that extends above the girdle and is generally off-set upward relative to the bark necrosis that reflects the xylem being plugged as part of the response to the cambium apoptosis (i.e., the signalling substance is carried in the xylem sap flow). I can only find this photo of the cross-section below the girdle that shows the discoloration in the wood. Maybe you can make a similar longitudinal section that does extend above the girdle and photograph it for us, @Cuzza (that is, if I am describing what has happened to your Sangokaku). I am quite certain you will find that the clogged-xylem discoloration extends well above the girdle.

2012-09-16 14.51.37-1.jpg

I likely have said in the past that this comes from ethylene signalling and I think that is not correct (@cbroad). Ethylene signalling is, however, responsible for leaf coloring and abscission.

Often we apply some rooting hormone to the upper edge of the girdle to 'kick start' the rooting process. IBA overdoses can cause dramatic coloration of the leaves above. I've dusted girdles with as much as 4.5% IBA and made acer palmatum and stewartia pseducamellia leaves dramatically turn brilliant red. We can make layers without any exogenous (from outside, applied by me, you) auxin. Because of PAT, auxin piles up at the top of the girdle. This accumulation causes the stem to swell there - an ethylene response. Hence, as @cbroad said,
Discoloration of the foliage is normal for air layers

So, what do we do about it? It is a question that I have been asking myself for a number of years because this sort of 'flame out' has happened to every layer I've attempted on my acer palmatum 'Higasayama'. Multlple attempts almost every season for close to 10 years now. Evidently, what one must do is leave a small/narrow bridge across the girdle; just enough to maintain the PAT. Too wide a bridge and the auxin is drained away from above the girdle, so that we no longer will have the high level of auxin needed to make roots grow. I got close with Higasayama this past season (the narrow bridge got to wide). It is such a blindingly obvious thing to do, but my prior experience was that layers failed (not catastrophically, just no roots) when there was any hint of 'bridging'. I tried applying auxin pastes at the bottom of the girdle, longitudinal cuts painted with IBA liquids, and carving 'windows' in the bark instead of a complete girdle that didn't work. Any bridge across a girdle will inevitably widen, so I/we must expose and renarrow it a few times during the season (of course, taking great care not to damage the nascent roots). I have yet to think of a way to avoid this.

... gawd, it is almost Friday already. I run on ...
 

Cuzza

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Thanks for the advice people. Not what i was wanting to hear but it would be pretty pointless just being told what i wanted to hear haha.

So going forward @0soyoung I take it this layer is a goner then? Any chance of saving it?
What did I do/not do that stopped it from working, since there's some nice long roots in the sphagnum moss...
Surely since others have success creating a separate tree with the same method I used there must be something I could pinpoint as it was all going so well..
(Sorry if you answered this above but I didn't quite understand)
 

0soyoung

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So going forward @0soyoung I take it this layer is a goner then? Any chance of saving it?
If the leaves on it are withered and brown, no
What did I do/not do that stopped it from working, since there's some nice long roots in the sphagnum moss...
Surely since others have success creating a separate tree with the same method I used there must be something I could pinpoint as it was all going so well.
You didn't do anything wrong, per se. It is just the way trees work.

There are two things I can think might give you a better outcome, next time.
  1. maintain a small bridge across the girdle, like I will be doing with my Higasayama (see the last part of my post above).
  2. place the girdle (ring of removed bark) immediately above a node (not immediately below one - again, see my post above for an explanation of why this may help you succeed next time).
 

Cuzza

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I see. Thank you again for your advice and patience. I know it must get frustrating.

I started this in spring and we have only just come into summer, I'm not so hot with understanding growth timings, but would it be possible to start a new layer now? Or am I waiting til bud break again?
 

0soyoung

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I started this in spring and we have only just come into summer, I'm not so hot with understanding growth timings, but would it be possible to start a new layer now? Or am I waiting til bud break again?
At this time of the season, definitely try again, NOW. You've got a lot of growing season left in a USDA hardiness zone 10.

If you don't have enough roots before leaf drop, just leave it on the mother tree over the winter. In this event, you will want to see the layer well leafed out next spring before you harvest it.

On the other hand, you may want to harvest the layer as soon as you see lots of roots (mostly filling the surface inside the bag). If there are not enough roots, it will, unfortunately, desiccate off the tree just like this one did on it. Taking a chance and finding out is the only way you can learn to recognize 'enough roots'.

I was lucky that my first air layer went swimmingly. Then the failures started happening, so I knew it couldn't be me at fault - LOL.

Don't give up
 

Cuzza

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Don't give up

Appreciate this. Starting to feel like everything that I manage to get going is failing on me out of nowhere. Or that the projects are never going to end up as bonsai. Guess I will just keep practicing failing until I start succeeding lol.

Will give another leader a try tomorrow.
 

0soyoung

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I've never had a problem air layering generic green acer palmatum nor with acer palmatum "Orange Dream". If you see one of these in a local nursery, you may want to grab it. They are good for bonsai too.
 

Shibui

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I've had layers fail when I've left them on the tree a bit too long. I put this down to the roots taking water out of the bag quicker than it is replaced leading to dehydration of the layer above? No blackening of the bark in these cases.
The blackening of the bark is a whole different thing. I also see this happen occasionally on Japanese maples that have not been layered. It usually starts at ground level and spreads around and up the trunk. Seems to occur as weather warms up in spring and may be associated with wet mix. I assumed it was a fungal infection. If the black has not spread too far some have recovered when kept a bit drier.
I'm suggesting it may not be too late for this layer. Open and check the roots and stem.
Stem only black below the layer is OK. Osoyoung told us above that dying back to the node below is natural when branch has been cut but it probably can't supply water and nutrients to the layer now it has died so definitely need to remove the layer and get it working as an independent plant with access to food and water.
Too dry? water well and see what happens.
If there's plenty of roots it is time to harvest your layer. Layers don't actually need a lot of roots to survive as they are primed to grow more roots really rapidly. I would reduce the amount of foliage above the layer to reduce the need for water and food while it recovers.
 

Wires_Guy_wires

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Maybe this will help someone, maybe it will not:
- If IBA fails, try NAA as an auxin. Some plants respond better to it.
- If there's a fast stress response that fucks up an ailayer, add vitamin C as an antioxidant. In some hard-to-root cultivars this can be the key to success. It slows down the plant killing off limbs.
- Sometimes auxins are more effective when used in combinations with cytokinins. At a 5:1 ratio of aux:cyt.
- Activated charcoal can soak up nasty metabolites (phenolic compounds) and render them ineffactive (stops future apoptosis/abscission). Coating the air layer 2-4 days after the first cut with AC could help sudden death. It also soaks up auxins, that's why it might be good to wait a few days.

I know that the options are limited, since there's only so many branches per tree.. Vitamin C does no harm in any way, so it can be used in any experiment without adverse effects.
 
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Are you sure the medium of the layered part is not too dry or too wet? I would open and check. Pack normal bonsai substrate around it if enough roots are present. Remove the layered part and try again if not.
 

AJL

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Everything was going great, I noticed so solid roots in the bag.. and then I noticed the whole top layered half has gone brown and a dry.. it's coming into summer now and I don't know if it's just sunburnt because it gets pretty hot here, or if it's because the roots tried out?? The bottom half is going great still with heaps of new growth and no leaf defects..
It sounds likely that the roots got cooked by the hot weather, leading to the airlayer top dieback. They can get very hot when wrapped in polythene and left in direct bright sun unless you partially shade the root wrap
Also as the mother plant is in a container your whole plant might have may well have become overheated and drought stressed which impacted on the developing airlayer roots
Suggest you move it into partial shade if its not too late?!
 

0soyoung

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It sounds likely that the roots got cooked by the hot weather, leading to the airlayer top dieback. They can get very hot when wrapped in polythene and left in direct bright sun unless you partially shade the root wrap
Also as the mother plant is in a container your whole plant might have may well have become overheated and drought stressed which impacted on the developing airlayer roots
Suggest you move it into partial shade if its not too late?!
I like this brainstorming you've done.

I can buy a simple meat thermometer probe at my grocery store for $5 to $15 - I presume you can do the same in England and so too could @Cuzza in Auckland. Get one, @Cuzza, and stick it in among the roots, in the bag of sphagnum of the layer and in the soil of the mother plant (near the pot wall would be best). Take note of the temperatures, the time and date, and the positions where you took the readings. Then you will know how real/irrelevant this is to your problem.

Temperatures above 95F/35C are not good for roots. The are certain to be dying when at 113F/ 45C or more.

Of course, we know that these temperatures will get the highest when the soil/substrate/sphagnum is dry. We also know that covering the bag of sphagnum and the black nursery pot will also reduce solar heating. Aluminum foil and damp, light-colored towels are two things people have used before.
 
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b3bowen

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There are two things I can think might give you a better outcome, next time.
  1. maintain a small bridge across the girdle, like I will be doing with my Higasayama (see the last part of my post above).

Thank you for the explanation above
@0soyoung it was very well written. Since leaving a small bridge across your girdle may be beneficial, do you think the Tourniquet method would do a similar thing, by only very gradually cutting off the auxin flow, and thus reducing the risk of failure?
 

0soyoung

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Thank you for the explanation above
@0soyoung it was very well written. Since leaving a small bridge across your girdle may be beneficial, do you think the Tourniquet method would do a similar thing, by only very gradually cutting off the auxin flow, and thus reducing the risk of failure?
I don't think a tourniquet will do anything of this sort because ultimately the stem grows under the wire until the cambium can no longer exist under it. I suppose there might be a monolayer of cambium cells under the wire that sustains PAT, but I haven't seen anything to persuade me that this might indeed be true. Tourniquets add a season or two to the whole process, so I have abandoned using them in lieu of a girdle. Preparation of cross-sections for microscopic exam at the cellular level seems a bit beyond my hobbyist abilities/equipment,

so the only way to know is to try girdle and tourniquet layers simultaneously on a number of trees, IMHO.
 
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