Rot in my Japanese white pine's rootstock

[shohin_branches]

I got two Japanese White Pines in 1 gallon containers that looked like could be nice prebonsai material but I've run into an issue. A large portion of the rootstock on one is rotting. Normally I'd spray with Physan 20 and pot it up but I don't want to harm the mycorrhizae. Currently out of lime sulfur. Any suggestions on the best approach to set this up for a good future? Currently carving out all the soft wood and prepping a pond basket.

 

[Japonicus]

IDK but obvious why you'd want to save it. Nice trunk and graft.
The cracks in the bark are concerning as is the large scale of rot. When did you get this?

 

[shohin_branches]

I would have updated earlier but I went out. Cleaned up the rot and reopened the edges of the scar with an x-acto and put some cutpaste on the edges to see if I can get some healing going. I got this a couple weeks ago and some needles started yellowing so I want to get it healthy and then I'll see about ground layering this above the rot eventually.



Here is the nob from the graft point.

So I got the knob cleaned up too.


Decided to go with a grow bag and no organic material to keep airflow good. I'm going to contact the seller to have a conversation since I just got these.

 

[bwaynef]

Inorganic soil is definitely the way to go. That looks like a REALLY big soil mass though. A weak tree won't be able to move as much water, so often they're put into as small a container as they can go to regain their vigor. There's something about quick drying cycles (without letting them excessively dry, mind you) that rejuvenates weak trees. It might be more that trees resent being wet, but whatever it is, I think your container is too big for this situation.

Also, whatever container you go with, you should make sure the tree is fastened in, rock-solid. I've had a hard time securing trees in grow bags with small rootballs.

If you choose to put it in a smaller container, I'd treat the rot with some peroxide-water (watered down to equal portions ...or weaker). Might be unnecessary, but probably won't hurt.

 

[Japonicus]

Yeh that's a nice tree

ground layering this

Only 2 cultivars are known to layer that I'm aware of.
Zuishio is one ofthose, I forget the other.

 

[bwaynef]

Yeh that's a nice tree

Only 2 cultivars are known to layer that I'm aware of.
Zuishio is one ofthose, I forget the other.

You're likely thinking of Kokonoe.

That said, I bought 2 JWP this spring with hopes of layering them in a year or so. They're neither zuisho nor kokonoe. Not sure it'll work, but I don't think its a necessarily a lost cause just because they aren't either of those 2 cultivars.

 

[Japonicus]

You're likely thinking of Kokonoe.

That said, I bought 2 JWP this spring with hopes of layering them in a year or so. They're neither zuisho nor kokonoe. Not sure it'll work, but I don't think its a necessarily a lost cause just because they aren't either of those 2 cultivars.

Please update with how it goes.
I hope it works.

 

[shohin_branches]

Roots on tree #2 are worse. It was slip potted at some point but the mat of roots are all black and squishy. There are a few live roots. I got as much of the rot removed as I felt comfortable with. Talked to the seller and they said if it goes bad they can replace it but not sure if I want another one of these.


Poorly trimmed dead and rotting roots.


I also didn't like the 3 gallon grow bag idea for tree #1. At first I thought I could water less but then realized that's not going to work with our cold wet springs so slipped it back into a 1 gallon.
So if you aren't feeling like dealing with root issues avoid the $65 JWP on ebay.

 

[shohin_branches]

Damn, did not realize I was clenching my jaw through that entire repot

 

[shohin_branches]

Inorganic soil is definitely the way to go. That looks like a REALLY big soil mass though. A weak tree won't be able to move as much water, so often they're put into as small a container as they can go to regain their vigor. There's something about quick drying cycles (without letting them excessively dry, mind you) that rejuvenates weak trees. It might be more that trees resent being wet, but whatever it is, I think your container is too big for this situation.

I agree. The root surface area to soil volume means that the soil can hold a lot more water than the roots can move efficiently. If the roots don't experience regular variation in moisture levels they won't grow to seek out water and your tree will languish at best but likely just rot.

I was thinking I could adjust my watering to compensate but my brain isn't what it used to be. When I was a kid I had over 250 trees in different states of development and I knew what I was doing with each one. In my 20's I had 5 to 10 bonsai trees because I was living in apartments and all my trees died when I left home. Now in my late 30's I have around 80 trees and I'm starting to write out notes for each because after a 10 hour workday the brain just doesn't want to think that hard anymore.

 

[shohin_branches]

Pine #1 is struggling the most. Candles are barely moving. It has lost a few more needles. Putting it back in the greenhouse to control the water.


Pine #2 looks like it will survive. Not the strongest candle growth, but it's enough to keep going after emergency surgery.

 

[shohin_branches]

White Pine #2 is recovering really well. The pond basket was the way to go for airflow. We've had such a wet spring and summer this year compared to last year.


White Pine #1 has okay apical growth but the side branch growth has all been very weak. I'm giving it a foliar feed weekly to get it healthy enough for surviving the coming Wisconsin winter. I keep putting it in the greenhouse because it's raining too often and the grow bag holds a lot more moisture. When the sun returns I run outside to get it back on the bench. The foliage it does have looks really healthy and needles have stopped turning yellow. I'm guessing this will be at least two more years of recovery if I can get it to survive winter.


Apical growth

auxiliary growth, womp womp

 

[shohin_branches]

In a turn of events white pine #2 which was doing great has suddenly started getting pale. I was confused a few weeks ago why it was dropping last years needles but seeing the color change this morning set off alarm bells. I'm worried the last two windy days and its bench location has dried it out too much. I've put it in the greenhouse for wind protection and applied a foliar spray. It will get a balanced fertilizer with the next watering instead of 0-10-10.

Pine #1 looks healthy just hoping to keep letting it grow and get more vigor.

 

[shohin_branches]

June 26th 2025 update

In another switcheroo pine #1 looked healthy until March when the color started to get pale. Im sure getting knocked off the bench twice last year didn't help. We had a tough winter. My heater couldn't keep up with the cold and that made keeping everything properly watered a little tricky. By May it was brown. RIP pine #1.

Pine #2 is still weak. Trying to keep it well fertilized so it can survive the next winter. Fairly worried this won't survive another harsh Wisconsin winter but I'm going to pile on organic fertilizer and see where it can get me.

 

[shohin_branches]

I've noticed that these grow bags seem to go absolutely nuts with mycelium.

 

[99 Mile Creek]

Ah...I lost my first white pine. Repotting, I believe, did it in.

Your second looks good. Interesting movement too.

 

[tanlu]

Org fert and full sun should help a lot. Another thing I would try if you really want to save it and get more growth is through it in the ground next spring. I grew most oftry to keep the trees I’m growing out in veggie grow bags inside large ceramic flower pots, planted on atop a mound. This keeps them stable during the windiest days, good drainage during wet weather, and reliably hydrated without my having to do much other than checking soil moisture every 1-3 days. I used more than 50% vermiculite in the soil mix + regular garden soil. My JWPs are growing on their own roots, so they need all the drainage they can get. They’ve been responding to this treatment with larger buds and plumper, vibrant foliage.

 

[shohin_branches]

Org fert and full sun should help a lot. Another thing I would try if you really want to save it and get more growth is through it in the ground next spring. I grew most oftry to keep the trees I’m growing out in veggie grow bags inside large ceramic flower pots, planted on atop a mound. This keeps them stable during the windiest days, good drainage during wet weather, and reliably hydrated without my having to do much other than checking soil moisture every 1-3 days. I used more than 50% vermiculite in the soil mix + regular garden soil. My JWPs are growing on their own roots, so they need all the drainage they can get. They’ve been responding to this treatment with larger buds and plumper, vibrant foliage.

Good suggestions, unfortunately I don't have a space to safely ground grow trees.

 

[bwaynef]

I've always been taught to withhold fertilizer until a tree shows signs of health. That one's showing mixed signals though. I wouldn't go crazy with the fertilizer, even if its organic.

 

[shohin_branches]

I've always been taught to withhold fertilizer until a tree shows signs of health. That one's showing mixed signals though. I wouldn't go crazy with the fertilizer, even if its organic.

That's a bit of a myth as long as you aren't building up excessive salts in the soil your tree will be fine. Denying a weak tree proper nutrients is going to harm the health more especially in 100% inorganic bonsai soil. Organic fertilizer doesn't pose the same salination risk that synthetic fertilizers do.

I also grow and sell carnivorous plants and they have a much lower tolerance to fertilizer and urea buildup in the rootzone. The main thing is to always monitor your plant and know the signs of when to adjust your approach.