air layer - what went wrong?

[eland]

Hi,

I tried an air layer this year on a Japanese maple for the first time this year. I made the cut in late June and wrapped it in moss. I did not put any rooting hormone on it b/c some have said it is unnecessary. As you can see it calloused but did not produce any roots. I have heard that Japanese maples are pretty easy to air layer so I was wondering if anyone could tell me what I did wrong.

 

[gergwebber]

keep that in some moist media and out of severe cold, it still looks alive and may root in the spring. no telling if it will make the summer, but???!!!???

 

[Bonsai Nut]

You don't want it to callous. You want it to throw roots. When it callouses it is healing instead of throwing roots.

Sometimes this means you didn't make your airlayer girdle wide enough (so the bark below and bark above doesn't heal across the wound) and sometimes it means that you didn't remove ALL of the cambium in the airlayer, or perhaps left some of the phloem.

When you girdle the tree you need to remove EVERYTHING down to and including the phloem. The removal of the cambium keeps the tree from healing. The removal of the phloem blocks carbohydrates and photosynthates from flowing down the trunk, and these excess materials gather at the wound site and trigger root formation. The level beneath the phloem (called the xylem) is what transports water and nutrients UP the trunk and is what keeps the part of the tree above the girdle alive. So you want to cut your girdle deep but not TOO deep. Fortunately the xylem is located in the deeper woodier layers of the trunk and it is pretty hard to cut too deep. In almost all cases air-layers fail because you girdled too shallow, or left some cambium or phloem behind.

 

[Bonsai Nut]

By the way... the part of the trunk beneath the airlayer girdle looks black(?) What happened there? Did you separate the airlayer before it had rooted?

I agree with gergwebber - you can treat the failed air-layer as a big cutting and see what happens. You never know...

 

[0soyoung]

I can't help but laugh, Bonsai Nut, though not meaning to be callous. Callusing cannot be avoided and always precedes the development of adventitious roots. For completeness I've attached a photo of the callus at the top of the girdle of a JM air-layer showing the nascent roots emerging from the callus.

Yes, girdling interrupts the phloem that transports carbohydrates (which are photosynthates). Importantly, it stops the flow of auxin (as IAA) from the leaves (not usually called a photosynthate). The accumulation of auxin at the top of the girdle is the driver for adventitious root formation and the reason, eland, why some think rooting hormone is unnecessary for air-layers (rooting hormone is a synthetic auxin).

I suppose you've got the basic idea about what can go wrong, Bonsai Nut, but you've confused things. The phloem is immediately under the bark. Under the phloem is the cambium and under that is the xylem (wood). Both the phloem and the xylem arise from cambial cells. Bridging, or growth across the girdle, is indeed the most common cause of air-layer failure. I've attached an example of this (from a bald cypress layer). Had this been eland's problem, eland's picture would have shown a line of callus across the girdle - clearly there isn't any bridging in eland's photo.

Bridging was not the reason for the failure of eland's JM air-layer. IMHO, you did a good job making the girdle, eland.

 

[Poink88]

Assuming the pic was taken recently...it looks like the main tree (or at least the part below the air layer) have rotted. I agree with gergwebber, it just might have enough to survive as a cutting esp if you can keep the root ball warm.

Good luck!

 

[0soyoung]

Hi,

I tried an air layer this year on a Japanese maple for the first time this year. I made the cut in late June and wrapped it in moss. I did not put any rooting hormone on it b/c some have said it is unnecessary. As you can see it calloused but did not produce any roots. I have heard that Japanese maples are pretty easy to air layer so I was wondering if anyone could tell me what I did wrong.

View attachment 27664

By the way... the part of the trunk beneath the airlayer girdle looks black(?) What happened there? Did you separate the airlayer before it had rooted?

I agree with gergwebber - you can treat the failed air-layer as a big cutting and see what happens. You never know...

Eland, I've been successfully air-layering JMs for several years now. I had the good fortune that my first attempts were wildly successful. Since then, I've come across puzzling and frustrating problems. I've still got an air-layer on an 'Aka Shigatatsu sawa', for example, that I girdled 3 seasons ago. I've recut it (i.e., removed the old callus) and I've used different strengths of rooting hormones to no avail. I am still in denial of the facts that rooting initials simply will not form on some species/varieties/cultivars when they are beyond a certain ontological age. But it seems to be a fact, just as the scholarly literature says.

I've also never succeeded air-layering my JM 'Higasayama'. I've tried repeately and every time the layer dies before roots are sufficiently developed, regardless of whether I used a rooting hormone powder or the strength (i.e., NAA/IBA concentration) I used. Everything seems to be going swimmingly until late August to early September and suddenly (in the span of less than a week) leaves are turning brown progressively upward from immediately above the girdle. Below the girdle, the bark has turned black just like yours did, eland. This is just die-back.

In many respects it is surprising that all air-layers don't fail this way. Among other things, auxin signals that the branch is alive. The layer girdle interrupts the auxin flow so there is none until contibuted by some foliage below the girdle. In this simple view it would seem that the cambium between that lower foliage and the bottom of the girdle should always die because there is no auxin (flow), yet this doesn't usually happen (except on my Higasayama). I've spent most of the last year trying to figure out what the additional signal is that keeps this 'auxin-free' cambium alive, but I still don't know how the tree "decided" to kill the branch. Nevertheless, you can see this in the first of the attached photos.

The other part of my 'mystery' and possibly yours too, eland, is why the foliage suddely goes brown. After all the xylem supplies water and nutrients and clearly it is still there. On the other hand, xylem is just a (Ted Stevens-esque) series of tubes - it doesn't take much to clog them up. I sectioned one of my recent Higasayama suicides and indeed there is a discoloration in the xylem that probably indicates the CODIT action (e.g., tyloses) that would go with the die-back. So, I rather suspect your branch/layer has the same. It might root as a cutting as is. Likewise if it is still on the tree, or just toss it; you can leave layers on trees through the winter, but in this case, it will simply be a dead twig/branch in the spring.

I still find air-layering to be an entertaining and educational adjuct to bonsai. I am going to air-layer my Higasayama again this next season but a little bit differently. I plan to dissolve some 1.6% IBA powder in an equal volume of water (making 8000 ppm) and then work this into a lanolin paste that I will 'paint' on the bottom of the girdle (while doing everything else in the same way). This ought to give an auxin flow into that cambium and, and thereby, avert air-layer suicide from recurring. Still I would like to know why this isn't always a problem.

 

[edprocoat]

I am not very familiar with deciduous trees, but isn't june a tad late to start an air layer.

ed

 

[eland]

Thanks for all of the replies! As I said this was my first time trying this and I guess that I hope that I just started it too late in the season. Osoyoung, we live in the same neck of the woods and was wondering when you tend to start air layers. What I read is that you need to wait until the leaves start to harden off. The confusing part for me was that the leaves hardened off at different times. The leaves that emerged first hardened off earlier than the ones that extended from the buds. Do you make the cut when the first leaves harden off, when they all harden off, or somewhere in between? Is it important to keep the air layer out of the direct sun, even though it does not get very hot around Puget Sound?

For those of you wondering if I kept it... It went into the big green bin. No buds formed like on the rest of the tree so i figured it was a lost cause.

 

[0soyoung]

I just started it too late in the season. Osoyoung, we live in the same neck of the woods and was wondering when you tend to start air layers. What I read is that you need to wait until the leaves start to harden off. The confusing part for me was that the leaves hardened off at different times. The leaves that emerged first hardened off earlier than the ones that extended from the buds. Do you make the cut when the first leaves harden off, when they all harden off, or somewhere in between? Is it important to keep the air layer out of the direct sun, even though it does not get very hot around Puget Sound?

It really doesn't matter much when the girdle is put in place. The only reason I can see for the traditional advice is that there isn't much in the way of auxin and photosynthates coming from the leaves until they've hardened. The auxin (IAA), especially, from the foliage is what drives the formation of the adventitious roots. Girdling too soon only means nothing happens until the leaves are cranked up (auxin and photosynthates are tranported toward the base of the tree in the phloem that you've removed).

The problem when you wait too long is that it doesn't leave enough time to get the new roots developed and functioning before fall. I think layer needs about 6 weeks on its new roots before leaf fall to survive, but this is more a prejudice than an established fact. It is only in this phase that shading the foliage is important

This year I made layers during the last two weeks of April. It takes at least 90 days to have enough root development to harvest the layer. Most of my layers were harvested in August, but the last one this season was cut off the mother tree on 30 Sep, which is getting a bit late.

I usually cover my layers with black plastic because the birds peck holes in the clear plastic and take off with my sphagnum otherwise. I have plenty, though, that I didn't and I cannot say that one way is better than the other. Observations with a meat thermometer probe in the spagnum would end any debate. Roots grow best at temperatures around 75F (like 65 to 80F).

 

[daygan]

In many respects it is surprising that all air-layers don't fail this way. Among other things, auxin signals that the branch is alive. The layer girdle interrupts the auxin flow so there is none until contibuted by some foliage below the girdle. In this simple view it would seem that the cambium between that lower foliage and the bottom of the girdle should always die because there is no auxin (flow), yet this doesn't usually happen (except on my Higasayama). I've spent most of the last year trying to figure out what the additional signal is that keeps this 'auxin-free' cambium alive, but I still don't know how the tree "decided" to kill the branch. Nevertheless, you can see this in the first of the attached photos.

Interesting conversation. 0soyoung, I'm far from a scholar in this matter, so just take these questions as curious wonderings: aren't auxins produced by meristems (non-differentiated plant cells)? and aren't cambium and procambium both meristems themselves? Wouldn't this mean that there is in fact a certain supply of auxins, and therefore also auxin flow, in the stem/trunk just below the girdle?

 

[Bob]

I don't know if it's relatable or helpful, but when I layer my crab, any branch under one half inch seems to throw roots but anything over a half inch seems to callous. I start the layers after the leaves have opened fully in the spring.

Bob.

 

[0soyoung]

Interesting conversation. 0soyoung, I'm far from a scholar in this matter, so just take these questions as curious wonderings: aren't auxins produced by meristems (non-differentiated plant cells)? and aren't cambium and procambium both meristems themselves? Wouldn't this mean that there is in fact a certain supply of auxins, and therefore also auxin flow, in the stem/trunk just below the girdle?

Daygan, neither am I a scholar. I just read their works. My understanding is that auxin, for all intents and purposes, is synthesized in the apical meristems (the leaves and root tips) – see this paper on auxin biosynthesis, for example. I think of all other cambial tissues as responding to auxin even though this is very simplistic ‘model’. Clearly there is a problem with this ‘model’ in the circumstance of the tissue below an air-layer girdle and above a node with active foliage. I think it is clear that there cannot be any significant (compared to what previously existed) auxin flow here even though there may be some low level of auxin synthesis occurring.

In addition to the Higa sayama experience, I’ve also had a case of two ‘identical’ air-layers this past season on a shishi ga shira in which one suffered this die-back (that eland experienced) and the other did not. Clearly it is not a specie-dependent phenomenon, though some species may be more prone to this than others. I agree that it is not simply low auxin level/flow or the die-back eland also experienced would always happen. I do think it is a precondition, though, else branches without foliage would never die. The CODIT response, I believe, is triggered by ethylene generated by this cambium as it dies. But, I have no idea what triggers the apoptosis.

Oh, I am getting repetitious. I could have spared you by simply saying “yes” and “yes” to answer your two interesting questions/points, daygan.

BTW eland. This paper (referred to above) indicates that it could be a good idea to girdle the branch before bud break (as opposed to after leaves have hardened off) – I’d forgotten about this. Still, I think it makes little difference exactly when you do it. The point is that nothing much is going to happen without leaves.

I don't know if it's relatable or helpful, but when I layer my crab, any branch under one half inch seems to throw roots but anything over a half inch seems to callous. I start the layers after the leaves have opened fully in the spring.

Bob.

Bob, I layered a two inch thick branch off an Orange Dream this season and have tended to air layer thicker branches because I thought these would get me to a bonsai-able trunk more quickly. I haven't done many layers on stems under one half inch. I do see some evidence of the juvenility cutting propagators talk about.

 

[nathanbs]

So if he had not cut it off was there any chance that it could have thrown roots during the next growing season?

 

[Poink88]

So if he had not cut it off was there any chance that it could have thrown roots during the next growing season?

From the looks of it, I think it would have continued to root...but runs the risk of getting frozen. JMHO.

 

[nathanbs]

freezing air layer

i guess i'm ignorant to that since I live in Southern California

 

[gergwebber]

you are already invested right? leave it in a protected site in a good porous mix and see what happens in spring. this may go well in spring, but I imagine summer will be a struggle. Any way it will be a good experience to see what it does. Many propogation guides for stone fruits speak of taking dormant cuttings and "callousing" them in a box with damp sand and cool temps untill spring when they are planted out. this will be a similar process, but it is already calloused...

Unless you already composted it?

 

[QuintinBonsai]

I too am trying to air layer a J.Maple, and I have the exact same problem as Eland. Except I didn't cut it before removing it from the rest of the tree. So what you're saying is, the calloused area should be scraped off, and another scraping around the air layer should be done? I know it's probably way too late in the season to attempt this, seeing as the tree is still very much alive and green, but I was just curious.

 

[0soyoung]

I too am trying to air layer a J.Maple, and I have the exact same problem as Eland. Except I didn't cut it before removing it from the rest of the tree. So what you're saying is, the calloused area should be scraped off, and another scraping around the air layer should be done? I know it's probably way too late in the season to attempt this, seeing as the tree is still very much alive and green, but I was just curious.

If you have the EXACT SAME problem as eland, the bark below your gridle is also black; NO the branch will probably never make it as an air-layer because the xylem is likely clogged.

If you have green bark on both sides but no roots, YES, but wait until next spring - nothing much is going to happen without any leaves. A dusting with rooting hormone might also be helpful then.

 

[Martin Sweeney]

Eland,

I have had better sucess using the turniquet method when air layering japanese maple (standard green leaf and coral bark) rather than the girdle method. I take a heavy piece of aluminum wire, single wrap around the trunk and tighten until there is some crushing of the bark. If I get uneven crushing of the bark (one side of the trunk only for instance), I wrap another piece of wire in the opposite direction and tighten. Then I cover with moist sphagnum, clear plastic and aluminum foil and wait. After checking 5 or 6 times prematurely, I will start to see roots in about 2-3 months. I have found that on faster growing japanese maples, normal trunk swelling at the wire allows for root development at about the same time frame as air layers with what would appear to be advantageous bark crush, so don't worry about getting the wire too tight.

I do not know what jap maple you are working with (and knowing probably would not increase the applicability of any advise I can offer you), but if I had a jap maple I wanted to airlayer next year, I would at least slip pot it to a larger pot to get stronger more vigourous growth and then try the turniquet method sometime around mid-May to mid-June here in North Carolina.

Good luck and regards,
Martin