Help Needed – Japanese Maple ‘Deshojo’ Showing Signs of Rot or Disease

[Noulinator]

Hi everyone,

I really hope someone here can help me. I’m deeply worried about my Japanese maple ‘Deshojo’, which is showing signs of what I suspect might be root rot, fungal or bacterial infection — and I fear it could be dying.

Recently, I noticed that the nebari has turned darker and slightly blackened, and some dark patches have started appearing on the trunk as well. I honestly don’t know if those marks were there before, or if I’ve only started noticing them now because of the nebari’s change in colour.

All the leaves on the tree look completely healthy — no wilting, no spotting, and no signs of distress when viewed from above. The issue seems to be limited to the trunk, bark, and nebari.

It’s worth mentioning that there was a recent storm with very strong winds, and it seems like the symptoms may have started shortly after that. In general, the weather has been cold, damp, and windy for quite a while, but now it’s becoming warmer and sunnier.

I’ve been fertilising with BioGold organic fertiliser, and until now the tree seemed fine. As soon as I noticed something was off, I removed all moss from the surface and also removed any remaining fertiliser. I replaced the top layer of soil with fresh substrate to increase airflow around the surface roots.

So far, I haven’t done more than that. I’ve also bought 3% hydrogen peroxide, but haven’t used it yet.

Right now, I’m unsure what to do next and would really appreciate some advice:

• Should I take the tree out of the pot and inspect the roots for rot, and remove anything unhealthy?
• Or should I leave the roots alone and instead water with diluted hydrogen peroxide to address any pathogens in the soil?
• Can I also apply the peroxide to darkened or suspicious areas of the nebari and trunk?

I did a small scratch test on the nebari, and the cambium underneath is still green, which gives me a little hope.

This tree means a lot to me — it’s my favourite — and I’m very upset about the situation. Any advice, even small suggestions, would be really appreciated.

Thank you so much in advance.

 

[Adamski77]

Couple of thoughts... and I'm not maple expert though I do have few.
- do you know/did you check how is this cultivar barking up? How is mature bark created... could be just next steps as the tree is aging. They do start from the bottom
- did you recently remove moss from this area? I can see on one photo something that looks like dried moss.
- I don't see any signs of distress on the top of the tree... leaves are healthy with no marks. Do you see difference this season vs. last season?
- when was last time you repotted it? Soil doesn't look compacted at all.

and last... don't inspect maple roots in the middle of the summer and stop scratching the bark... me personally would start with that...

 

[Shibui]

Trunk changing from green to brown/grey is normal as the bark matures. No problem there.
One roots does look a little black. Sometimes that can indicate a problem but, often it's just moisture changing the appearance of the outer bark of the root. The green under the bark is a positive sign but I definitely agree with @Adamski77 Scratching through the bark only opens a way for any pathogens to enter the sap stream and puts your tree at even more risk.
Leaves are all happy and healthy so another good sign.
Remembering that root rot takes many weeks of constant soggy soil, have you been overwatering enough to be truly worried about root rot?

If your root ball will lift out of the pot reasonably easy you can check the bottom of the root ball and then just slip it right back in. That will not cause any harm to the tree and may just alleviate your worries.

 

[Noulinator]

Couple of thoughts... and I'm not maple expert though I do have few.
- do you know/did you check how is this cultivar barking up? How is mature bark created... could be just next steps as the tree is aging. They do start from the bottom
- did you recently remove moss from this area? I can see on one photo something that looks like dried moss.
- I don't see any signs of distress on the top of the tree... leaves are healthy with no marks. Do you see difference this season vs. last season?
- when was last time you repotted it? Soil doesn't look compacted at all.

and last... don't inspect maple roots in the middle of the summer and stop scratching the bark... me personally would start with that...

I have no idea how this cultivar barks up… not sure where to find that information :/

Yes, it was completely covered with moss.. i removed it all, and put some fresh soil on top to improve airflow.
Moss was also on the nebari.

I just got the tree this year. I dont know when it was repotted.

Trunk changing from green to brown/grey is normal as the bark matures. No problem there.
One roots does look a little black. Sometimes that can indicate a problem but, often it's just moisture changing the appearance of the outer bark of the root. The green under the bark is a positive sign but I definitely agree with @Adamski77 Scratching through the bark only opens a way for any pathogens to enter the sap stream and puts your tree at even more risk.
Leaves are all happy and healthy so another good sign.
Remembering that root rot takes many weeks of constant soggy soil, have you been overwatering enough to be truly worried about root rot?

If your root ball will lift out of the pot reasonably easy you can check the bottom of the root ball and then just slip it right back in. That will not cause any harm to the tree and may just alleviate your worries.

Is it normal for the green patches to turn Dark/black/purple when they turn to bark? Thats what worries me. I have no idea how deshojo “barks up”
ChatGPT says that Japanese maples can go Dark purple almost black when the clorophyll leaves the trunk as it develops bark. No idea of it is true?

Took some fresh pictures today trying to show the dark colours developing on the green part of the trunk.
Also the nebari is still very dark at some spots. It wasn’t this dark to begin with… as mentioned it has been very stormy weather and moist.

Regarding overwatering, I am really not sure. I think it has fooled me with a dry surface thinking it was probably more dry that it really was…

I really appreciate your feedback!

 

[PA_Penjing]

tree looks pretty happy to me

 

[Contact]

It's becoming "older"...It seems ok

 

[Shibui]

Took some fresh pictures today trying to show the dark colours developing on the green part of the trunk.
Also the nebari is still very dark at some spots. It wasn’t this dark to begin with… as mentioned it has been very stormy weather and moist.

Regarding overwatering, I am really not sure. I think it has fooled me with a dry surface thinking it was probably more dry that it really was…

Still can't see anything out of the ordinary that I'd be worried about. If it had root problems you would almost certainly be seeing some branches with wilted and dying leaves.

The soil mix appears to be akadama and pumice so should be hard to overwater but I understand that akadama can break down over time, leading to much more water retention. Any idea how long since repot/ fresh potting soil?

Dry surface has fooled a lot of new growers and a few more experienced as well. Need to get to know how each mix reacts by checking below surface level or by keeping a wood stake/chopstick in the soil so you can remove and check below surface moisture levels.

At this stage I don't share your pessimism. The tree appears to be happy and healthy.

 

[Noulinator]

Still can't see anything out of the ordinary that I'd be worried about. If it had root problems you would almost certainly be seeing some branches with wilted and dying leaves.

The soil mix appears to be akadama and pumice so should be hard to overwater but I understand that akadama can break down over time, leading to much more water retention. Any idea how long since repot/ fresh potting soil?

Dry surface has fooled a lot of new growers and a few more experienced as well. Need to get to know how each mix reacts by checking below surface level or by keeping a wood stake/chopstick in the soil so you can remove and check below surface moisture levels.

At this stage I don't share your pessimism. The tree appears to be happy and healthy.

The upper layer of the soil is my own mix. I removed the moss it had, and replaced it with a thin layer of akadama, pumice and lava.

What worries me is the darkening of the nebari. The sun is not shining on the tree yet, and I was able to take some pictures in a more accurate light.

I have no idea when it was repotted last time.

I attached some pictures of the tree from march, before the nebari turned dark and the current ones I took today.

The tree still seems to be fine except for this.. i believe the blackening happened after we had a stormy weatherwith wind tracking 19-20 meters pr second and rainy days.
I did prune the tree 22 days ago with sterilized tools.

 

[Shibui]

Adding a new soil on top of the old can cause complications when watering, especially when you cannot accurately tell if the soil is still wet or dry. Fortunately the original soil appears to be an open, free draining bonsai type mix so hopefully it still ahs plenty of air spaces and doesn't stay totally wet.

I can definitely see the black you are worried about but still not convinced it is a sign of a problem. Hopefully just normal maturing or possibly some reaction to something in the water.

I'll have a look at some of my older JM bonsai to see if any have similar dark bark.

 

[Adamski77]

Yes, it was completely covered with moss.. i removed it all, and put some fresh soil on top to improve airflow.
Moss was also on the nebari.

that's what I thought... and I think it could be main reason why you have this discoloration. Tree looks pretty happy... just stay calm and patient... water carefully and watch...