Here is a very old post of mine to the IBC on just this subject. It later became an article at my website.
>>>>>
At 06:32 PM 5/19/97 GMT, you wrote:
> I've read about pruning and pinching in several bonsai books as well
>as in the IBC archives, and I'm still not sure what to do. I must be
>pretty slow, but I wonder if someone out there will have pity on me and
>guide me through this in really simple language. Thanks a lot, and please
>be patient if my questions seem silly.
> I got a Chinese elm a month ago and lopped off the top, leaving it
>branchless. I'm satisfied with the thickness of the trunk. It's about six
>inches high now and I'd like to keep it under ten inches. Leaves are
>beginning to burst out at eight or so spots around the cut on top or
>within an inch or so of it. I'd like to end up with a broom some day.
First let me say that I am not a big broom style fan. If the trunk is
perfectly straight, then sure you can make a broom from it. If it has any
trunk movement, it will probably make a better informal upright.
1) It seems to me as if six or more leaves are coming out all at once
>from each of the spots on the trunk. Should I start pinching them back
>now? Or should I wait until the beginnings of a branch develop? And
>exactly where should I pinch? Right where a leaf meets the branch? If
>there are six leaves coming out together, which of the six should be
>pinched? The ones closest to the trunk or the ones farthest from it?
First, let's discuss the role of 'pinching' as opposed to 'pruning'. Pruning
is used (with reference to branches) to shape the branch, change the
direction of the branch, and create taper within the branch. This is all
done by pruning back to a bud aimed in the direction that you want it to go.
This is usually done to a shoot with several internodes to be removed or
with a larger lignified (woody) existing branch. It doesn't matter if you
use concave cutters, your fingers, pruners, or chain saw, as long as you do
a neat job.
Pinching can achieve the above for very small branches on some species, but
for the most part, when we speak of pinching, we are talking about achieving
ramification, or twigginess. In this case the scaffolding of the branch is
complete, it only needs detail work or ramificication. This is done by
removing the tip of the growing branch, usually removing two nodes of a
three node shoot. This does two things: 1) it shortens the branch. 2) it
releases the buds behind it. Remember Apical Dominance? The buds are held
from opening by the release of a hormone manufactured by the terminal (last)
bud. It is abscissic acid if I remember correctly, but anyhow, now the
remaining bud is free to open AND the buds behind this one.
The result is that by pinching out the terminal bud, or removing a two or
three bud shoot, several of the buds remaining on this stem are free to
open. Usually one or two will open before the new terminal bud starts
forming the hormone and stops the process. Thus, where you once had a soft
straight shoot with INCREASING internodes (usually), you now have two buds
opening forming a forked branch with shorter internodes and achieving
ramification.
I emphasized INCREASING above, because what most people have never bothered
to observe (at least I never see it mentioned) is that the first two or
three internodes of a released bud (achieved by pruning) are shorter than
the internodes of the rest of the expanding shoot. By pinching back to one
or two buds we take advantage of this phenomenon, keeping the short
internodes sections and discarding the strong shoot with the longer
internodes. This is most important as we reach the outer portions of the
branch which, like the branches on the trunk itself, should have leaves and
nodes closer together as we approach the extremities.
Armed with knowledge, you will be able figure out how to achieve your goal.
But of course you have to know what your goal is, and that is always the
most difficult part, especially for beginners who have not seen enough trees
to know what they want to do.
In addition to this, some knowledge of the species is important, because not
all woody species react in the same way to pruning (although in general they
do). There is also the major distinction that divides the woody species,
those that have alternate leaves (buds), and those that have opposite.
Alternate species are in general easier to work with, since the last bud
will open before the one before it. This creates a strong main branch
extension from the last bud and a weaker smaller branch fork (secondary)
from the next to last bud. Just keep this in mind and nature will do the rest.
In opposite species, the two buds are directly opposite each other and will
often open simultaneously with equal strength. If not corrected this will
give a fan pattern rather than a strong branch, weak secondary pattern
usually desired for bonsai. If one bud is nipped out as they expand, one can
mimic an alternate
species. The same thing is achieved in the training of Black Pine, where
great care is taken to make sure that all the branches fork, where in nature
they would form whorls, and only after many years of wear and tear would
they be reduced to forked branches.
Now I will try to answer some of your questions directly.
> 2) At what point do I prune the actual branch itself? Some sources
>say after two or three or four internodes.
As above, this is for ramification, not necessarily for main branch formation.
>What about if there are three
>or four internodes in the first inch of the branch? Should I prune there
>or wait until the branch is a couple of inches long? Will the branch keep
>growing straight out if I lop it off at the end?
You must form a branch before you can ramify it. It doesn't matter how many
internodes are in the first section of the branch, the only thing that
matters is whether the branch will sprout from where you cut it to form a
bend or create a secondary (side branch) and a new main extension. In
general, if you remove the end of a branch, or otherwise prune it, you will
change its direction, since a bud on the side of the branch will break and
start the new extension in a different direction, the same is true for
chopping the trunk. If you want a straight branch, don't prune it.
> 3) When people talk about nipping buds at the end of a branch, what
>do they mean? How much of the branch should be left leafless? The last
>quarter inch? Half-inch? Inch? If you nip the buds at the end of the
>branch, exactly where on the branch do you let the leaves grow?
Pinching buds at the end of the branch, means just that. Remove the ONE
terminal (and its leaf) and leave the other buds and leaves alone. The bud
at base of the next leaf will be the first to open and form a new shoot in a
new direction. The rest of the branch may or may not have leaves, it is of
no concern to us here. Perhaps you are confused about what constitutes a
branch and terminal bud. A branch for pinching purposes constitutes one
straight section, or twig, with buds and possibly leaves but with NO side
branches. Each branch, twig, or shoot if you prefer has only ONE terminal
bud, at the very end of the shoot.
> 4) I've probably failed to ask a few important questions. If so, I'd
>appreciate it if someone would go ahead and answer them for me anyway.
> Again, thanks a lot, and please don't laugh at me for asking a lot of
>questions that must seem obvious to you.
The other thing that you need to know here is how Ulmus parvifolia grows in
response to pruning. What you have probably already learned is that this
species is dense with buds (called adventitious) embedded in the bark as
well as the single bud contained in the leaf axil. When you prune this
species, you get branches all over the place. This is the beauty of this
species for bonsai, and also the reason I tell folks not to worry about
branches until the trunk formed, since you can easily get branches wherever
you want them by simply pruning it hard.
You now probably have a little fuzz ball of branches. These are very soft
and succulent, and there are very many more than you need. If you begin to
prune them off as they emerge you weaken the plant and many of them will die
back. Let them grow out about six or eight inches so they can harden and
have a better chance of surviving. At this stage you can remove the ones you
don't want and start thinking about what to do with the ones remaining. The
discussion above should help you. If you want one to fork at a certain
location, prune it there. You can see that you must have an image of the
tree that you want to obtain before you can proceed.
Brent
Evergreen Gardenworks Northern California USDA ZONE 8 SUNSET ZONE 14
bonsai@pacific.net http://www.pacific.net/~bonsai