Peeling Bark on Maple

[girv]

I bought this acer last year at home depot for $30 and so far it has been doing great, but this week noticed a few issues. The bark near the soil line was separating from the tree, and when I went to inspect further it came right off. The bark on the roots underneath are also black and after repotting earlier, mostly dead in that section. This was not in the best soil so felt it was time to get into something better. When reducing the roots, I took off a decent section of taproot and noticed the black area. I have pretty minimal experience with maples but my first thought was Verticillium, however the tree has seemed healthy otherwise minus some black spots (pictured) which I have noticed since picking it up. Would be sad to loose this one, all feedback is appreciated.

 

[0soyoung]

When the cambium dies on acer palmatum, the bark gets a dark color and 'weepy'. Shortly thereafter it dries and the bark is strongly glued to the xylem (wood) underneath. When the cambium around this area again starts growing, it lifts that dead bark and it will then easily flake off.

Trees compartmentalize damage. The cambium's dying act was to emit a chemical signal to surrounding tissue to seal off the damage. Fibers in the phloem tubes clog the sieve plates/ Living cells sprinkled throughout the wood either extend part of themselves or exude compounds that clog and seal off the xylem. This is the dark wood area shown in your first pic. The lighter colored wood is the 'live wood'.

So, all this happened before you bought the tree and simply escaped your notice. I will grow over and not be visible to you, in time. Everything in your final (farthest right) pic looks pretty normal to me. Carry on.


btw, every wannabe wants to scream 'verticillium' - it almost never is verticillium.

 

[girv]

Thank you @0soyoung for all the feedback and info! Thoughts on if I should remove the dead bark and cambium or leave as is? I tried peeling back a bit more and no live cambium in sight.

 

[0soyoung]

Not necessary. It will take care of itself pretty much automatically.
But, it is strangely satisfying to dig at it - a lot like picking one's nose.

 

[girv]

Forgot what I think might be a big component of this... I am trying to air layer this tree on the main trunk about 8 inches up to remove some reverse taper and create two trees. I attempted this back in May and it still has not took.

 

[0soyoung]

I presume you did this with damp sphagnum wrapped in plastic and that you, @girv, are not seeing new white roots in the bag. I suggest that you open it up and carefully part the wad of sphagnum to see what is happening. The usual cause is that the girdle (the ring of bark you removed back in May) has been bridged - remove it, and scrape the area again. If you don't see any nascent roots, I suggest you then leave it open for at least a day - until next weekend would be fine. This will desiccate and kill any residual cambium cells on the exposed wood more easily and effectively that just about anything else.

If, on the other hand you find lots of roots that are just too short to appear under the plastic, gently close it all back up, and now wait for another month or so. You should then see lots of roots in the bag, just under the plastic - cut if off and pot it up.

Lastly, if you don't see enough roots (or any) in a month or so, you can just leave the works in place over the winter. I've had layers take as long as 3 seasons to generate a harvest-able quantity of adventitious roots. In your climate, you likely will need to wrap something insulating around the plastic covered wad, bubble pack, rockwool, even damp sphagnum, etc.

 

[girv]

@0soyoung I have read quite a few of your posts on the topic(thank you!) and after opening it up, there was callused growth, no roots, and some bridging. I originally started the air payer back in early May. I scraped the bridged area, wiped with alcohol, reapplied rooting hormone and instead of using wrapped sphagnum again, opted for a pot with bonsai mix in it. I have not watered it yet as it seems like waiting a day or two isn't a bad idea.

My concern at this point is that the dead cambium area at the soil line was never-ending, and the bottom of the girdle seemed like dead cambium as well. I can attach some photos, but at first, was only worried about losing the air layered section, now I am concerned with losing the whole tree. There is only one small branch under the air layer at this time so curious if this eventually kills all cambium. I can attach a few photos of the tree if helpful but the girdle is already covered back up.

 

[Shibui]

It is almost certain that the root below that dead area is also dead. I have seen this a number of times. Not sure whether the infection gets in through the root which then kills the part of trunk above or the other way round.
The trunk above looks healthy so the extent of the dead zone must be limited. As mentioned, trees can seal off infected areas to prevent spread and I guess your tree has done that or the damage would be larger or fatal by now.
I don't think finding the edges will do any good but it may satisfy you to see just how large this dead area is. The dead bark will all lift in time if you just leave it alone but if you feel the need to investigate just dig off dead bark a little at a time until you come to live area.
Looking at that dead root on one side I think this tree will probably not make bonsai status with one side of the base dead but hopefully you can get a replacement with the layer and maybe another if you layer the trunk again above the dead area after it regains health.

 

[0soyoung]

Looking at that dead root on one side I think this tree will probably not make bonsai status with one side of the base dead

It could be invisible in back
It could be hollowed out --> storybook it!
It can also be closed, eventually --> hort tour de force
It could also be the ground side of the start to a raft bonsai --> brilliant

And, this is also a good idea.

maybe another if you layer the trunk again above the dead area after it regains health.

My concern at this point is that the dead cambium area at the soil line was never-ending, and the bottom of the girdle seemed like dead cambium as well. I can attach some photos, but at first, was only worried about losing the air layered section, now I am concerned with losing the whole tree. There is only one small branch under the air layer at this time so curious if this eventually kills all cambium. I can attach a few photos of the tree if helpful but the girdle is already covered back up.

Your pic of the tap root only showed death about 25% of the way around. If it was only alive 25% around, I would be worried.
You are right that with only one branch feeding the roots, there is some risk that the roots starve to death during the process - don't remove any foliage from that branch.

If you want, post a pic of what is bugging you now. Maybe @Shibui and I can talk you through it. It is good that you're observing and thinking things through, but you shouldn't be loosing sleep.

 

[girv]

I won't be throwing the tree away prematurely so we will see what happens and use it as a learning experience, hopefully it survives but I am thinking that a lot more than 25% is dead and the cambium seems to be toast all the way up to the airlayer on that side... I had a tough time controlling the moisture level in the air layer and I am thinking the poor soil most likely retained too much water as well. Now that it is in bonsai soil and I redid the air layer, all I can do is wait and see!





Bad angle but the top portion might make a good formal upright when rotated a few more degrees.

 

[0soyoung]

So, @girv, at the girdle, there is a full ring of cambium, all the way around the trunk?

The tree looks reasonably healthy to me. Foliage is maybe a bit sparce, but let it grow and don't do any pruning until the end of the season.

Good luck!