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For Beginners:
Trunk Chopping 101 For Deciduous Trees

by Andy Rutledge, U.S.A.

One operation that every bonsai artist has to perform from time to time is the trunk chop. It is seldom that you will be able to make a bonsai without making some large cuts on the trunk. This is especially true if you work with trees of any significant size.

Larger trees need to be cut back and made more compact to be of use as bonsai material. Sometimes the upper trunk is removed in favor of a smaller shoot that will serve as the new leader. In other cases, the trunk is cut back to a point where there is no potential shoot. In this case you have to wait and see where one or more buds will pop to form a new leader.

There are right ways and wrong ways to cut the trunk of a potential bonsai tree. In this article, I'll detail the best methods for chopping the trunk of most deciduous trees, like maple, bald cypress and elm.

Timing

The best time for most trunk chops is in mid to late spring or early summer (depending on your geographic location); after the new leaves have formed and begun to harden off.

Case 1
Cutting back to an existing leader a tree suitable for a chop

a tree suitable for a chop

Here we have a likely candidate (above). This tree already has pretty good taper, but it is too tall for bonsai purposes.

Until now, you've been growing the trunk for size and you're ready to begin its transformation into a bonsai. You've decided to cut back the trunk to an existing small branch that will be the new leader (indicated by the red arrow).

Use the saw and cut a little bit above the branch. Be careful not to damage the branch that will become the new leader.

The following images show a detail of right and wrong ways to make this cut.

cut 1

Good
Cut back to a bit above the new leader.

cut 2

Use a cutter and then the grafting knife to reduce the wound to the shape shown here. The rounded gouge can be used to create a channel around the interior perimeter of the wound so that the callus starts by rolling into the wound. Be sure to apply cut paste to the wound.

cut 3

When it has healed, the transition from the scar to the new leader (that has now grown thicker and has been cut back) is natural looking.

cut 4

Bad (above)
A cut at the level of the new leader must not be left straight.

cut 5

When the wound heals and the new leader grows thicker, there will be an ugly, flat transition and the new leader will bulge above the old scar. This is not natural looking.

Case 2
Cutting back with no existing branches

A straight trunk that you want to cut back.

A straight trunk that you want to cut back.

Here you have a straight trunked tree; perhaps an elm or a bald cypress.

On this tree, you may want to cut the trunk back to a point where no branches are growing. You will have no new leader and will have to wait for buds to form and create a new leader. You hope that a bud will form in the correct place, but you don't know what the tree will do.

In this case, since you cannot be sure where a new shoot will grow, you should not work too fast and begin your taper. Instead of cutting on an angle, cut straight across.

The following sequence of illustrations shows what can happen if you do things right of if you do things wrong.

Mistake!

This is a mistake! (above)
The following images will show you why.

cut 6

Oops!
When the new shoots emerge, they may or may not grow where you would like them to.

No shoot emerged at the top of the tapered slant. This presents a problem...

cut 7

…and here's the result. The shoots did not emerge at the top of the tapered slant, so now the trunk has died back to where the shoots did grow.

This is not likely what you had in mind and your options are now severely limited.

Instead, cut like this.

Instead, cut like this.

Good!
This is how you should cut the trunk in this case. This way, you are not committed to any one front or any particular branch configuration.

This allows for many possibilities.

Applying cut paste to the large wound can help in preventing dieback, which often occurs before the new buds form.

cut 8

Now when the new shoots emerge, you have your pick of which to use for the new leader.

cut 9

After you've chosen a leader and removed the others at its level, you can then shape your trunk to accommodate the future growth of the leader/trunk.

The shaping of the wound is done just as in the previous example. The new leader and the trunk will eventually form a natural looking transition.