Understanding layer failures

[andrewiles]

I've tried a bunch of layers this summer on different species to learn the ropes. Lots of successes and some failures.

Hoping folks on the site can provide some insight into the failures.

I've seen three types of failure:

1. Branch immediately wilts and dies
2. Branch stays healthy for a few weeks or months, then wilts and dies
3. Branch stays healthy indefinitely but no roots form.

Most interested in #2 at the moment. I've seen this on some japanese maples and a pond cypress. It appears the xylem is functioning well enough, for a time, then dies. Pond cypress example:



In this case the layer was started on June 8 and it was clearly wilting and dying by late July. Early and mid July looked healthy.

You can see lots of callousing but the remaining sapwood has eventually died. I tried not to cut very deep when removing the cambium but this is a small branch so perhaps that is an issue.

Any thoughts on what can cause this sudden death?

 

[andrewiles]

Oh, and the layers that failed were treated with the same technique and aftercare as many that succeeded.

"Rainy Day" vine maple:


Dawn Redwood:

 

[WNC Bonsai]

I had one fail on a J. maple this summer. It did fine for over a month then the top just died. In this case it was a very thin stem and I suspect there wasn’t enough sapwood water transport to sustain the top. My other J. maple was a success and was about the same thickness. I also layered a Chinese elm, slippery elm, and two zelkovas successfully so I just chalk it up to the stem being too small.

 

[andrewiles]

Yeah, I'm thinking that this problem is tied to the stems I'm practicing on being small and young. Maybe 2 seasons old for both failures. Perhaps some species need a few seasons of growth to generate enough xylem to survive the process.

 

[rollwithak]

In my experience, japanese maples have been very hard to perform air layering on. Not sure why. But guessing it’s fairly normal because most nurseries will graft instead of air layering JMs.

 

[WNC Bonsai]

In my experience, japanese maples have been very hard to perform air layering on. Not sure why. But guessing it’s fairly normal because most nurseries will graft instead of air layering JMs.

I think they graft in order to place a less vigorous variety on a much more vigorous one. For example many use the more common generic green J. maple for root stock as it grows more vigorusly and they can get a larger plant more quickly by grafting onto it.

 

[Ohmy222]

I think they graft in order to place a less vigorous variety on a much more vigorous one. For example many use the more common generic green J. maple for root stock as it grows more vigorusly and they can get a larger plant more quickly by grafting onto it.

Though you are right that many are weaker or their own roots, the real reason is grafting is a much higher percentage method of propagated over cuttings. Seedlings are not an option for cultivars. It is easy to grow 1000s of Acer palmatum seedlings and graft onto them. Species that root easy like azales are rarely grafted.

 

[BobbyLane]

i did a few layers in may on copper beech and green beech all using the same methods. only the green beech had so much roots it was separated a few days ago. i checked the 3 layers on the copper beeches and not a single root! nor do the girdles look like they want to callus over. and the trees are super healthy and full of foliage. so ive just wrapped them back up and will look again next season. but i might re do them with fresh moss in may 2022

 

[Ohmy222]

I had one fail on a J. maple this summer. It did fine for over a month then the top just died. In this case it was a very thin stem and I suspect there wasn’t enough sapwood water transport to sustain the top. My other J. maple was a success and was about the same thickness. I also layered a Chinese elm, slippery elm, and two zelkovas successfully so I just chalk it up to the stem being too small.

I don't think the size has much to do with it unless they are really twigs. I do very small ones all the time. Only problem with a small one is they may be weak and can break easy. I find maples to be easy to layer overall have found some cultivars to be harder. I find the dwarf varieties and rough bark ones to be the easiest to root which is counter intuitive. I do have failures on some of the larger leaf varieties and red maples like Tsumi Gaki, Bloodgood, Osakazuki but if you rewound them then they will finally root. They are slower. I have only had three die above the layer, a Korean Maple 'Aureum', a smaller Arakawa branch, and a collected Hawthorn. Elms and Zelkova are bulletproof so if you are comparing to them then yes maples are harder.

 

[yodamon]

Hi. I was reading intensely to understand your failures so I may glean some insight. I do finally had a success. I started 5 maple air layering's on April 3rd. I lost one every 2 weeks until I had one left. I let it root until August 3rd and then cut and planted it in a clay pot. I struggled with removing a lot of leaves after the cutting (as I knew I should) but it lost just a few and is mostly green and healthy. Waiting for the fail or the new growth.

 

[andrewiles]

Hi. I was reading intensely to understand your failures so I may glean some insight. I do finally had a success. I started 5 maple air layering's on April 3rd. I lost one every 2 weeks until I had one left. I let it root until August 3rd and then cut and planted it in a clay pot. I struggled with removing a lot of leaves after the cutting (as I knew I should) but it lost just a few and is mostly green and healthy. Waiting for the fail or the new growth.
View attachment 392448View attachment 392449

Looks like a decent set of roots to me. I think maybe the bag could be a bit larger with more Sphagnam moss, given the size of the branch. I'm still learning as well. After I separate I've been placing the layer in light morning sun and gradually moving to stronger sun if I don't see any wilting. I'm trying not to remove any leaves after separation, since the leaves continue promote root growth.

 

[leatherback]

I struggled with removing a lot of leaves after the cutting (as I knew I should)

Why do you think you should? I normally let the branch sort it out itself. Give it shade & no wind for a week or two so the roots can start to establish in the pot. But removal of foliage? Only if the thing it too tall to be stable.

 

[0soyoung]

I've seen three types of failure:

1. Branch immediately wilts and dies
2. Branch stays healthy for a few weeks or months, then wilts and dies
3. Branch stays healthy indefinitely but no roots form.

Most interested in #2 at the moment. I've seen this on some japanese maples and a pond cypress. It appears the xylem is functioning well enough, for a time, then dies

For the most part, the physiology of CODIT (Compartmentalization of Damage In Trees) explains these troubles.

Another detail is PAT (Polar Auxin Transport) which explains why auxin 'piles up' at the upper edged of the girdle. Interestingly both branch tips and root tips are auxin producers. The biologically involved auxin from branch tips and leaves only goes down the tree in a bucket brigade from one cambium cell to the next.

Auxin also exists in the phloem tubes along with the carbohydrates produced by the foliage, but it doesn't 'count' until it is removed by a daughter cell and made part of the PAT stream. There is no down-coming PAT stream immediately below the girdle, so PAT tends to remove all of the auxin from cambium cells here. At some point there is not sufficient auxin for these cambium cells to survive, so they die and in the process signal to nearby cells to compartmentalize the damage (die also). This is the same process that occurs after pruning a branch, which we note by 'die back'. Species that can rapidly transport stuff upward in the phloem (via phloem pressure working against gravity) will live longer than others. #2

Obviously, we kill cells when cutting/scraping tissues. Just scraping the wood to eliminate cambium kills living cells in the wood and they do their CODIT thing as well as some others in the vicinity. With young stems, that only have one or two rings of wood, this can cause all the xylem lumens to be plugged. Further whittling away wood to a similar point can cause the xylem to be shut off. #1

The remarkable thing is that cells specialized to that divide and then be differentiated into wood and bark (cambium cells) can get reprogrammed to be a root tip! For this to happen their DNA activations must be erased (to make them into stem cells) and then set to be a root apex. It seems reasonable that dedifferentiation is a process that some species may do more readily than others (if for no other reason than why should it be identical for all?) --> hence some species may not root. #3

 

[andrewiles]

That's fascinating. So for #2 there is a CODIT message that's slowly diffusing latterally from the open wound into the rest of the xylem. This explains why an air layer doesn't live forever once the cambium is removed. And would explain why a thicker branch, with more rings, would last longer against this process.

Out of curiosity, do you have a horticultural degree? Must be nice to understand tree physiology at this level

 

[0soyoung]

Out of curiosity, do you have a horticultural degree?

No, I do not. I'm a retired physics/engineering guy. It is just fun finding things out, IMHO.

old dog
new tricks

I started with a successful air layer and then turned into an air layering maniac. And then came the same story for me as the OP, but I spent winters with Google Scholar finding some answers as well as new questions that led to experiments the next season. Rinse and repeat. Every season also produced a new 'accident' or two.

However, addressing my lack of artistry (or inability to express myself artistically) was at the heart of why I took up bonsai. I faced up to that promise several years ago and now am a different kind of maniac. I'm trying to make pretty trees. Again, again, and again. I've produced a few trees that now smile back at me, but is still very difficult to do and Google Scholar is of no help.

 

[andrewiles]

Yeah, I'm a software guy. A methodical and logical profession. The mental contortions necessary to focus on bonsai are not small! But that's why it's so appealing.

Love the Anacortes area by the way.

 

[yodamon]

Why do you think you should? I normally let the branch sort it out itself. Give it shade & no wind for a week or two so the roots can start to establish in the pot. But removal of foliage? Only if the thing it too tall to be stable.

I thought I should because of several videos. I didn’t though. I believe your thought of letting it sort itself out is a good one. I moved it to the shade, under a shady plumb, and it has been three weeks now and I think it has turned the corner into a independent tree. It is too tall,4-5 feet but secured to a stake and out of the wind. Thanks