Help with Trunk Development

dbonsaiw

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I have a JM with a fairly straight trunk that has been growing out (base is 2.5" and tapers to 1.6"). I'd like the tree to ultimately be about 15" tall and would like to start adding some movement to the trunk. I'll be chopping down the trunk late winter and am looking for guidance on next steps, specifically adding movement to this straight trunk. I included a pic of the tree with two potential options (additional ideas welcome). The blue line is the proposed cut (about 5" from the soil and I am more than happy to cut lower) and green lines are branches.

In terms of movement, how does the development differ if (i) the cut is made straight and branches allowed to grow directly opposite one another from the same node ring or (ii) the cut is ultimately corrected to a diagonal cut with first branch growing below and from a separate node ring from the new leader?
 

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Brian Van Fleet

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First, can you repot the tree and change the planting angle so the first trunk section isn’t straight up?

Second, if you chop where you suggest, you’re really counting on back-budding where there isn’t any right now. It’s a gamble. I would suggest a thread-graft into the spots where your green lines are that will guarantee something is alive to chop back to. Otherwise, an option is to chop higher, wait for back-budding at existing dormant nodes, and then chop back again to growing shoots.

Third, any chop would be better made in the late spring, after growth has started.

Your question about angled vs. flat cut: when you cut, the tree will die back to the next living node. That’s why often times a chop will result in the next trunk section growing, while the back side dies back to the ground. If you cut back to existing shoots on either side, you control the dieback; whether that is an angled cut, or a flat cut. For example, look at this post of my trident maple. See how a shoot developed at the base of the cut in that 3rd photo:
That’s what stopped the dieback on the back side. I have kept that branch (always short) to keep the trunk alive and to help close the would above it. Here is a shot of that branch now, 8 years later:
 

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dbonsaiw

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First, can you repot the tree and change the planting angle so the first trunk section isn’t straight up?
I repotted recently and not exactly sure how to get the tree out of the bonsai soil when the roots haven't filled it yet. I'm concerned I will do root damage pulling the roots out of the pumice etc.
Second, if you chop where you suggest, you’re really counting on back-budding where there isn’t any right now. It’s a gamble. I would suggest a thread-graft into the spots where your green lines are that will guarantee something is alive to chop back to. Otherwise, an option is to chop higher, wait for back-budding at existing dormant nodes, and then chop back again to growing shoots.
I'm not wed to branches in any specific place at this point. It would be a shame, however, to cut it down and for no shoots to grow. Does that happen often?
Third, any chop would be better made in the late spring, after growth has started.
I've never been clear on this issue. Always just thought that late winter cut provides vigorous growth and larger internodes, and late spring gives smaller internodes.
 

SeanS

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I'm not wed to branches in any specific place at this point. It would be a shame, however, to cut it down and for no shoots to grow. Does that happen often?
I’m not sure if it happens often, but it happens. I chopped a trident mid summer last year and nothing happened. It was still alive come spring so I grafted some seedlings to the stump to keep it alive. You can follow the operation and it’s progress in my trident thread. Scroll the pages to see it’s progress this season, it’s growing well now!
 

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One other comment in response to your specific question.
The cut is angled or flat is often dependant on the desired outcome and location of existing buds.
For example if one desires a single trunk upright style than a bud can be selected and an angled cut made to encourage the existing bud to become the new apical line for the single trunk.
If one desires a multi - trunk style such as broom than the flat cut will be initially made to encourage buds on the outside rim of the flat cut. Select the ones desired to grow out and carve between them later on for a more convincing transition.

Previous comments with respect to having a lower branch or existing buds to cut back to are important to pay attention to. The strategy of staging the cut back to give a chance for bud back before going lower is wise as well.

For clearer instructions and explanations several of these techniques are discussed in Merrigioli Bonsai maples with useful accompanying diagrams for the steps required.
 

Brian Van Fleet

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I repotted recently and not exactly sure how to get the tree out of the bonsai soil when the roots haven't filled it yet. I'm concerned I will do root damage pulling the roots out of the pumice etc.

I'm not wed to branches in any specific place at this point. It would be a shame, however, to cut it down and for no shoots to grow. Does that happen often?

I've never been clear on this issue. Always just thought that late winter cut provides vigorous growth and larger internodes, and late spring gives smaller internodes.
When did you last repot it? They can certainly handle annual root work, especially when young.

Since your goal is to add movement and taper to a straight trunk, the easiest and most obvious start is by changing the planting angle.

It does happen that a tree will fail to respond to a trunk chop. JM are less vigorous too, so if you want to chop, I’d suggest not just whacking it down to 5” tall and hoping for the best. It’s a gamble, if it lives, and where it buds to an extent; buds will appear at nodes, if they appear. Can you still see the old nodes in the trunk?
 

dbonsaiw

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I’d suggest not just whacking it down to 5”
This seems to be the consensus, so I will chop higher to begin with and see what grows. How low should I go? There's probably 3 feet of trunk until you hit the first branch.
Can you still see the old nodes in the trunk?
I can still see rings all the way down to the root flare. I would assume the tree is less than 10 years old.

When did you last repot it? They can certainly handle annual root work, especially when young.
My concern is not so much the timing of the cut, but the physical removal of the roots from the soil. When the soil is filled with roots, the whole thing comes out of the box and I can rake away the soil. Here only a fraction of the box is filled with roots - I would effectively have to shovel the tree out of the box.
 

dbonsaiw

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For clearer instructions and explanations several of these techniques are discussed in Merrigioli Bonsai maples with useful accompanying diagrams for the steps required.
This book was probably the best bonsai purchase I made to date. I've been through the book, certain sections multiple times. For every question I had that he answered (and there were many), two more popped up. Some of my questions will only be answered with actual hands-on experience.

I do recall, however, him discussing formation of the "mighty trunk" and the need to chop the trunk almost to the roots. He didn't seem to express a concern that the tree wouldn't back bud at all. Rather, my recollection is that the only issue he expressed was one of possible die-back passed the lowest node. For those who have this concern, his suggestion was to initially chop only a little bit higher and then correct the cut later in spring. Note that his suggestion was to cut late winter and to cut down to a stump.
 

Brian Van Fleet

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This seems to be the consensus, so I will chop higher to begin with and see what grows. How low should I go? There's probably 3 feet of trunk until you hit the first branch.

I can still see rings all the way down to the root flare. I would assume the tree is less than 10 years old.


My concern is not so much the timing of the cut, but the physical removal of the roots from the soil. When the soil is filled with roots, the whole thing comes out of the box and I can rake away the soil. Here only a fraction of the box is filled with roots - I would effectively have to shovel the tree out of the box.
You could chop it down to 12” or so and see what pops and chop again.
Looking through your other threads, it appears that the answer to my question about when it was last repotted would be sometime between last fall and last month, yes? If so, definitely wait until late spring or early summer so the roots are strong enough to withstand the sawing motion, and have grown enough to support a next growth flush. Otherwise you’re just going to kill it.

2 tips:
1. It’s important to do the right work in the right season.
2. When you’re building a tree, always always always build it from the nebari up. That means that the root work you did last fall is where you should have started designing this tree.

Did you get the roots combed out radially? Are they on a single plane? Are they roughly the same size all around? Did you identify a best front based on the nebari? If not, don’t bother chopping the trunk down to the final height this year, chop it to 12” or so and then in March 2023 (yes, 2023), start over with proper root work. Then when you find the best front based on the nebari, you should have some branches to select for the next trunk section and an opposing primary branch.
 
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dbonsaiw

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2 tips:
1. It’s important to do the right work in the right season.
2. When you’re building a tree, always always always build it from the nebari up. That means that the root work you did last fall is where you should have started designing this tree.
Thank you for the advice. I will chop down to about a foot and work from there.

This was the first tree I purchased for bonsai purposes. it was from a big box and was horribly pot bound. I had zero clue what I was doing and made a bunch of mistakes in respect of timing, soil etc. At the last repot I cut the tap roots and downward growing roots. I tried to leave one line of roots, but not 100% sure what I left at this point. I will likely need to rework the roots in the future.
 

dbonsaiw

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definitely wait until late spring or early summer so the roots are strong enough
That is what I will do, or simply leave it to grow for another season. In the interim, anything wrong with taking some airlayers? I’d like to have some of the same material to graft with the following year.
 

Brian Van Fleet

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That is what I will do, or simply leave it to grow for another season. In the interim, anything wrong with taking some airlayers? I’d like to have some of the same material to graft with the following year.
Should be ok if that’s all you plan to do this year.
 

dbonsaiw

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Should be ok if that’s all you plan to do this year.

Could I do a few thread grafts on the lower portion of the trunk and also air layer?

Looks like I will have a number of trees recovering/growing out this year, so I will take some cuttings later in the winter and then some air layers. This way maybe I'll get a few trees started and some grafting material for the following year.
 

Brian Van Fleet

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Could I do a few thread grafts on the lower portion of the trunk and also air layer?

Looks like I will have a number of trees recovering/growing out this year, so I will take some cuttings later in the winter and then some air layers. This way maybe I'll get a few trees started and some grafting material for the following year.
Probably
 

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