Trunk Chop 101?

[dbonsaiw]

As I mark off the days on the calendar waiting to make my first ever trunk chops on some Japanese maples, I realize I don't know what I don't know. Understanding that there are always differences of opinion, I was wondering if the more experienced folks can shed some light on what I would call "trunk chop 101" issues.

I've been letting the trees grow a bit to fatten the trunks some more, but how much additional trunk growth can be expected after the chop as the bonsai develops. Clearly this is a "how long is a string question", but is a little more specific than that. For example, if I cut a 2 inch trunk, do I practically lose the ability to grow say a 6 inch trunk through sacrifice branches? I'm trying to get a feel for how long I should keep trees in the ground if I have a general caliper size I am looking for in the base of the tree.

Some more "wet behind the ear" questions - there seems to be some disagreement (at least when the new leader isnt already growing) as to whether the cut should be made straight or angled, at least initially. Unfortunately, it appears even the experts disagree on this. What are the pros and cons of each?

Finally, I am unclear about the relationship between die-back, the trunk chop and clean up of the angle. I understand that maples generally die back to a node. So the cut is made somewhat above a node to allow for the die-back. When the cut is angled (initially or in clean up) I assume one has to cut passed the node on which the new leader is growing and presumably that doesn't lead to die-back that would kill the new leader.
If the trunk is cut straight, when is the dead portion removed/new angle made? Does this lead to further die-back?

Sorry for the really basic questions.

 

[Wulfskaar]

If I may piggy back on this with a question of my own...

At what diameter of trunk/branch do you use a saw instead of clippers?

 

[leatherback]

Cut at a right angle to the trunk.
Do not trunk cut in winter. Let the tree leaf out, and cut then. You will get slower re-growth, but fater healing & closer internodes. At that time of the year, you could risk an angled cut, but I would let a branch grow where possible.

Cutting lower and ofter gives you smaller cuts and slower thickening but can still get you a thick trunk

 

[Bonsai Nut]

For example, if I cut a 2 inch trunk, do I practically lose the ability to grow say a 6 inch trunk through sacrifice branches?

A quick comment about this one point...

Change your perspective about sacrifice growth. It doesn't have to be letting the apex run - it can be anywhere. You could grow a nice maple bonsai that is 12" tall, then decide you want the trunk to thicken and get more taper, and grow a big sacrifice branch out of the lower back of the tree while still maintaining the existing upper part of the bonsai with its existing apex. Remove the sacrifice growth, and you have a scar in the back of the trunk that will have to heal over time, but only you will know it is there

The other thing about maples... you can actually get them to grow outwards at the soil line - particularly if you plant them on a tile and spread the roots radially. As the tree grows, the roots will get correspondingly thicker, and the trunk at the soil line will broaden substantially.

 

[rockm]

Chopping the tree will dramatically slow increase in diameter of the remaining trunk. THe more growth above the roots, the faster the increase in diameter. That is why chopping is done ONLY when the lower portion has reached the diameter you want in the final bonsai.

With an initial chop, CUT STRAIGHT across an inch or more ABOVE where you want the apex to begin. That will give maximum room for new buds to emerge in more places. It will give you more choices when you're choosing one to grow on to become the next extension of the tree (Maple and other deciduous trees involve MULTIPLE trunk chops to force taper into the trunk in a short space.).

Cut in spring. Seal the cut.

 

[dbonsaiw]

Many thanks for the responses. As I understand the above comments, letting the tree grow wild is what develops the best thickening of trunk, but the trunk can still be thickened at least somewhat after the chop. Cut straight and do it in the spring after leaves have have leafed out. I will definitely get these guys on tiles after the next repot.

So what happens to the die-back after the cut and how is the angle of the cut adjusted after the initial chop to improve taper?

 

[leatherback]

the trunk can still be thickened at least somewhat after the chop

A tree does NOT stop thickening. EVery year is adds. How much it adds is realted to the amount of growth above the trunk. Cutting makes for slower thickening. But even a tree cut every year will each year increas substantially if left to grow for the year, and given space & fertilizer.

So what happens to the die-back after the cut and how is the angle of the cut adjusted after the initial chop to improve taper?

Once you have a branch, you can slope the cut to match the trunkline. Cover with cutpaste and wait for it to grow over the cut.

Befor cutting


A few years later, grown over

 

[kale]

Great thread! I have a jm about 2” thick at the base and am thinking its going to be time this spring. Can I chop almost at the base or do I need to chop above nodes?

 

[Shibui]

A tree does NOT stop thickening. EVery year is adds. How much it adds is realted to the amount of growth above the trunk. Cutting makes for slower thickening. But even a tree cut every year will each year increas substantially if left to grow for the year, and given space & fertilizer.

I agree.
Growing straight, fat trunk really thick then chopping leaves a huge cut which will take many years to heal and to grow an entire new apex. I find it much better - and faster in the long run - to chop regularly. retain a number of new shoots after a trunk chop. Each will add trunk thickness. If the total new shoots = the removed single trunk thickening will continue as before but at the next chop each individual cut will be much smaller and therefore heal quicker. In addition you can selectively prune to get a good start on trunk taper and some better trunk bends/movement. Even if regular pruning slows initial growth by a year or 2 (and I am not convinced this is actually true) you will more than save those years when developing the complete trunk and apex. I am happy to show examples of trees grown using this technique.

Initial cut is straight across because you cannot predict where new shoots will grow. Refine the chop at an angle after the new shoots are growing strong and you can choose a suitable new leader. Wait until the chosen leader is growing strong before completing the angled cut. Strong sap flow to the new leader will prevent further die back.

The other thing about maples... you can actually get them to grow outwards at the soil line - particularly if you plant them on a tile and spread the roots radially. As the tree grows, the roots will get correspondingly thicker, and the trunk at the soil line will broaden substantially.

Trunk buttress thickening is amazing when the tree relies mostly on lateral roots but a board is not needed. Selecetive root pruning to remove down roots and encourage laterals works just as well, possibly better as you are controlling the roots better. When down roots are removed they do not grow back strongly. After a couple of selective root prunes I do not find new vertical roots growing, even when trees are planted in grow beds.

Great thread! I have a jm about 2” thick at the base and am thinking its going to be time this spring. Can I chop almost at the base or do I need to chop above nodes?

Maples can only ever shoot from nodes or where old nodes were originally. Chop too low and older JM sometimes fails to shoot. It is usually safe to cut 6"-8" above roots because there would have been plenty of nodes in that area when the tree was a seedling but to be really safe chop above a branch and hope for more shoots lower that you can chop back to later. Radical reduction pruning can be staged over a number of sessions and years.

 

[dbonsaiw]

Shibui, if you have pictures of the progressive trunk chop, I'd love to see those.

 

[Shibui]

I have photos of a great many techniques but not sure I have kept enough photos over a number of years to show progressive trunk reduction. Sorry.

 

[dbonsaiw]

I have little experience with growing new leaders, but have wired branches. I notice that no matter how straight up I wire it, the part of the branch coming out of the trunk always has a bend. Will this eventually grow into a straighter leader (not formal upright necessarily, but just not so far out to a side)?
Also, is there a way to describe the differing effects that different cuts would achieve? For example, if I have a 5 foot tree, what are the practical differences of (i) chopping it down to 5 inches and growing a new leader from there; (ii) chopping it to 6 inches or so and then cutting it down later to 5 inches (I assume that's just to activate the node of the new leader); and (iii) chopping it down say a foot every year (allowing it to grow wild in the interim) until its 5 inches?

 

[leatherback]

I notice that no matter how straight up I wire it, the part of the branch coming out of the trunk always has a bend. Will this eventually grow into a straighter leader

Nope. Best is to either keep it in the front (and the cut sonsequently in the back) or use the bend to create movement in the trunk.

For example, if I have a 5 foot tree, what are the practical differences of (i) chopping it down to 5 inches and growing a new leader from there; (ii) chopping it to 6 inches or so and then cutting it down later to 5 inches (I assume that's just to activate the node of the new leader); and (iii) chopping it down say a foot every year (allowing it to grow wild in the interim) until its 5 inches?

1) risk of dieback to lower regions. If cutting to the exact height you want, make sure you do it in the growing season to reduce dieback, and ideally to existing buds. Best to take nr 2
2) No big difference with 1. Assuming you cut back within a year or so, you loose very little healing time
3) Makes little sense. You get a big chop down low no matter what. All you do is increase the waiting time for the lowest cut to start healing. It does require you trusting the tree to create buds below the cut.

 

[dbonsaiw]

Much thanks. These answers really clarify a great deal.

 

[Tums]

Many thanks for the responses. As I understand the above comments, letting the tree grow wild is what develops the best thickening of trunk, but the trunk can still be thickened at least somewhat after the chop. Cut straight and do it in the spring after leaves have have leafed out. I will definitely get these guys on tiles after the next repot.

So what happens to the die-back after the cut and how is the angle of the cut adjusted after the initial chop to improve taper?

If you were going to chop after the tree leafs out, what I've heard is usually to wait for early summer/6-8 weeks after bud break, otherwise the tree won't have recouped any energy from its first set of leaves. The other timing suggestion from @rockm was probably in spring before the tree leafs out which would give faster coarser regrowth.

 

[Ohmy222]

A quick comment about this one point...

Change your perspective about sacrifice growth. It doesn't have to be letting the apex run - it can be anywhere. You could grow a nice maple bonsai that is 12" tall, then decide you want the trunk to thicken and get more taper, and grow a big sacrifice branch out of the lower back of the tree while still maintaining the existing upper part of the bonsai with its existing apex. Remove the sacrifice growth, and you have a scar in the back of the trunk that will have to heal over time, but only you will know it is there

The other thing about maples... you can actually get them to grow outwards at the soil line - particularly if you plant them on a tile and spread the roots radially. As the tree grows, the roots will get correspondingly thicker, and the trunk at the soil line will broaden substantially.

View attachment 405395

I have always had the opinion a sacrifice down low would cause the nebari on that side to grow larger too. Not certain but it seems when one side has more branches, the roots below it seem to be bigger so I normally stick with apical sacrifices. Curious the thoughts of others.

 

[sorce]

the trunk is cut straight, when is the dead portion removed/new angle made?

It depends how much and what type of growth you end up with above it, but there is a time when if you don't remove the excess wood, the tissue you want to cover the wound will begin to bulge out.
The purple representing that tissue.

Removing the excess wood as close to right before this tissue visibly begins to bulge is best, earlier would risk further "dieback".

I find that the natural angle of "dieback" is almost always best to trim back to after a straight cut, I've never seen a angle cut first look good later.

Important to note that I don't recommend chopping to buds up here.

There's no reason at all to not chop back to branches except Impatience.

We simply don't have the time up here for a bud to grow into something that will put on enough tissue to cleanly cover a wound.
If we do get something so vigorous to heal the wound cleanly, it has uselessly long internodes.

Size matters.

Pics!

Sorce

 

[River's Edge]

I like the way Andrea Meriggioli addresses the question of formation techniques for Maples. Essentially he notes that there is a wide variety of techniques available to aid in developing many styles. He devotes a full chapter to formation techniques describing when a flat cut is useful and when an oblique cut will be most beneficial. Also illustrates the multiple pruning steps that can be involved in trunk formation.
Essentially not one way!
Some styles benefit from trunk chopping straight across initially and finishing with angle or "V" shaped cuts. Some develop quickly with apical sacrifice and other styles require lower sacrifice branches. Often multiple techniques are applied within the same development over time.
Great written resource for those who may wish to expand their techniques to develop trees that display variety of development.


BONSAI MAPLES Author Andrea Merriggioli published 2019

 

[Hack Yeah!]

I think the Braves chop is best, at least this year! 2021 world champions!

 

[dbonsaiw]

I find that the natural angle of "dieback" is almost always best to trim back to after a straight cut, I've never seen a angle cut first look good later.

That is a seriously important piece of info you shared. Much thanks.

River's Edge, thanks for the recommendation. Any further reading recommendations? I've been going through Peter Adam's book on Japanese Maples and learned a good deal.

Attached are 2 pics of one of my "Acer HomeDepotnium" trees (purchased at a big box store with similar name). It was the first I purchased and the trunk is almost 2" in diameter. I didn't properly deal with his roots when planted and will comb them out and maybe cut the tap root etc. (right before spring????). There's some nebari on opposite sides that has been covered a bit by wind, watering. This will be my first ever trunk chop.

I've purchased some more of these trees this season and got them into larger pots. At $15 for no less than 1" caliper and an array of foliage among the plain vanilla green JMs, I simply couldn't find better trees to learn on. Also keeps my bonsai nursery-bought trees safer from my impetuous nature (a guy's gotta cut something!!!).