Everything they taught you in pruning school is wrong.
Well, maybe not everything. Let me make it clear that this is about pruning bonsai – not yard trees. This is not
for arborists or arborist wannabees. And some of the things they say are correct. But we are styling bonsai - not 10 to
100 foot trees - and we are styling and shaping our trees so we have very different objectives. So if you wandered onto
this site from thru an internet search and want information about lawn trees, go elsewhere. Many of the pictures below
are adapted from the internet and were correct in their context.
The Goals of pruning
There are many different reasons that we prune bonsai and each reason has a different technique. Our trees are
small (small is a relative term and one can see the different sizes of bonsai on another page) and there must be routine
pruning to maintain the size and shape we desire while promoting the health of the tree. When making heavy cuts for
styling different rules will apply. There are quite different goals and thus procedures for making styling cuts on
deciduous versus conifers. More correctly I should say plants with and without jin and shari or plants where we want
wounds to heal completely or plants where deadwood is a feature of the plant.
Maintenance pruning should consist of many small cuts all over the tree and none of those cuts will require wound
care. They are usually done with scissors or by finger plucking. The majority of that work comes in the spring, though
it is ongoing throughout the growing season. There should be visible lightening or opening up of the tree. Branches
and leaf pads should be better defined. A bird should be able to fly thru the tree.
The most simple maintenance pruning is the daily or weekly pinching of buds where they are unwanted or
unneeded. The new growth on junipers can be pinched back every day you look at them because there is always more
to come. Long shoots of new growth should generally be cut back to encourage branching. After flowering, every
single flower bud should be pinched off of azaleas, so you pay dearly for a year when they are covered with flowers.
One switches from finger-tip pinching to fine scissors on going to maples, elms, crepe myrtles and others. In the
spring, maples want to put on lots of new growth. There can be two, three, or more pair of leaves on a greenwood
maple shoot. It is important to get the shoot clipped back to the first pair of leaves quickly because the entire length of
the green shoot is extending as it puts new growth on the end. The first pair of leaves might be tight to the branch when
there are only two pairs of leaves on the shoot, but if
you wait until there are four or more pair of leaves,
the first two leaves will be much farther from the
branch. Good ramification requires constant pruning.
On maples, it is also important to cut the stem
back very close to the pair of leaves. One will expect
to get two new branches when trimming back to a pair
of leaves. If the cur is farther down the stem, the twig
will die back to the point of the new branches but will
remain on the tree and be unsightly. It will probably
drop off in the next season, but why wait when more
careful trimming will take care of it immediately?
The next level of maintenance pruning involves
cutting back small branches. If there are a series of
buds down a branch, you might want to prune back to
just a few. The cut in Figure 1A is cut too high, but
for bonsai, so is the cut in Figure 1C which is
recommended by arborists. The best cut in this case is
the middle one (Figure 1B) and where the initial cut
appeared to be a bit higher, but then a second, more
horizontal cut removed a bit of the remaining point above the bud. The middle cut, properly trimmed, will heal nicely
putting a curve into the branch at that point as the remaining bud becomes the new leader. Hopefully, there are several
additional buds farther back the branch to provide additional branching
There are few trees that reduce as well as Chinese elm (ulmus parvifolia), but this requires careful pruning. In
nature, the leaves are up to two inches long. With constant pruning to maintain very small branches, the leaves can be
maintained at less than half an inch. The elm provides a very good illustration of why maintenance pruning is
important. In the spring, when the new shoots first start, the first two leaves can be under a quarter of an inch and each
successive leaf will be larger, going out the shoot. If one keeps the tree trimmed back so that every branch tip has only
two to four leaves, then all of the leaves will have the desired diminutive size. Letting runners go will fatten up a
branch more quickly, but there will be a price to pay in leaf size.
What arborist is ever going to tell you that you should cut all of the leaves off your tree? You would laugh them
out of your yard or maybe report them to the Better Business Bureau.
Complete defoliation of a tree may seem like a drastic step but there are times where it can be quite beneficial. In
the late spring when a maple is lush with new growth, it is possible to remove all of the leaves and much of the
greenwood. This step will promote back-budding to generate a considerable number of new small branches. Leaf sizes
on the new branches will be considerably smaller than before the defoliation. I have several shohin maples that have
leaves that are disproportionately large. Annual defoliation keeps the leaves in proportion to the tree.
Finally, I must admit to several accidental defoliations. Most of my better trees are protected by a fence, but some
trees in progress are on benches exposed to deer. If I am on vacation, my trees are watered automatically, but not if a
deer has pulled the tree off the bench. On more than one occasion I have found completely dehydrated maples lying on
the ground. The leaves may be crunchy, but if the tree is cared for, it will come back and there will be new buds at the
point of most of the old leaves. The new foliage will be
delightfully small. This is an effective but not a recommended
Pruning for Healing
Pruning for healing is the objective for all arborists. Pruning
for healing is the objective for deciduous trees and pines where the
objective is to have the wound heal over completely and blend into
the silhouette of the tree. For good healing, it is imperative that one
get a good clean cut with no ripping of the bark.
If one is using scissors to make the cut, then there is now
issue with the wound. If one is using a diagonal or concave cutter,
then the branch is small enough and the cut is quick enough that
there will ne no ripping of bark. If there is any straining with the
cutter, then the cur is big enough that the branch should be cut with
a first cut leaving a knob and then go back and finish the cut
approaching the trunk carefully and making sure the bark around
the cut has a good clean edge for improved healing.
If the cut is large enough that one is going to use a saw, then one should use the arborist method using a three-cut
approach. The three-cut method shown in the figure is the best way to initiate the cut. Cut A is to protect the bark
below the cut. Cut B removes the branch. Cut C provides the final wound that an arborist would prefer because it heals
quickly. The arborist will stop here expecting the branch to heal over, being unconcerned about the resulting knob on
the tree. It is pointed out that cutting any closer to the tree will damage the “healing ring” around the branch.
The three-cut technique shown is an issue in bonsai because it leaves an aesthetically unappealing knob on the
tree. That is the reason that we have concave or knob-cutters. For a thick-skinned tree a flush cut might suffice but for
a tree that develops a strong callous, a concave cut is required. Hollowing out the wound slightly will leave space for
the thick fleshy callous. As a result we are required to damage the healing ring which will make healing more difficult.
The first next step for a good bonsai cut is to clean up the edges of the wound with a very sharp knife or razor blade.
Smoothing the wound promotes healing all the way around. Finally, the wound on bonsai should be covered with a
flexible cut paste even though the tree industry now recommends against covering wounds.
A B C D
Figure3: Four examples of branch cuts. A) A cut that would make an arborist cringe, but in fact, it is a perfectly suitable cut for a bonsai
showing deadwood. B) A cut that is unsuitable in all cases. Three-cut pruning described above avoids this worst case. C) The arborists
perfect cut that will heal well. It will leave an unsightly knob on a bonsai. D) A bonsai cut that will heal nicely leaving a minimal scar
on the tree. The cut may be flush or slightly concave and the edge of the wound is cleaned up with a sharp knife.
There is no way an arborist would want to generate deadwood on a tree – but it is an essential part of several
bonsai styles. The reason that we do junipers is for the drama of deadwood to show what a difficult life the tree has
survived. Jin on branches and shari down a trunk are the two types of deadwood. Usually, a tree should have neither or
both. The death of a branch will often lead to death of the live vein that fed it so jin should often lead to shari. And
there is seldom only one piece of jin on a tree.
Arborists do their three-cut pruning so that the live vein below a branch is not injured, but in nature branches are
ripped off trees by the weight of snow or by wind. There should be purposeful generation of shari below a broken
Jin is easily generated by cutting a branch off some distance from the trunk. Squeeze the branch with pliers to
crush the cambium layer. After crushing, it will generally peel off the branch quite easily. Feel free to pull the bark
right down the trunk to create a scar below the branch – this is the way it looks in nature.
There is nothing as unnatural as a dead branch with a perpendicular cut on the end, so after peeling the bark,
grab the branch in your pliers and twist it to create a jagged break. If it is too large to be broken, peel off strips of wood,
mostly from the bottom side, to leave a raw jagged look. Long thin jin means that the branch has died recently. We
want trees to look old, so the jin should look aged and this is achieved by making it shorter relative to the diameter of
After jin and shari have been aged for a while, they should be painted with relatively concentrated lime sulfur. At
first, this will result in unnatural-looking yellow deadwood, but within days, the lime sulfur will turn white. Deadwood
in the high Rockies can be very white, but if this it too white for your sensibilities, it can be toned down a bit with a
wash of very dilute, black India Ink.
Stumping is something that no arborist will do. Their nearest term for it is “cutting down the tree.” For them, it is
a terminal act. Any shoots that come up from the stump are an unwanted nuisance and they will often grind out the
stump to remove any evidence of the existence of the tree.
Though not for the feint-of-heart, stumping can be a useful technique in bonsai. It is the act of cutting the tree
back to a useful section of trunk – no branches – and praying for new buds to form around the cut. Stumping should
generally be carried out in the spring before the tree has wasted any energy on new growth because it is going to need
everything it has to push out sufficient new growth from the stump. There are mixed messages about how to promote
new growth. I simply seal the cut and often wrap the edges with plastic tape to force all of the new growth vertical
rather than have it bur our horizontally. Others suggest that the cut be kept moist with wet cotton or sphagnum until the
buds are well established.
The technique works well with maples, elms, hornbeams and zelkova. They bud reliably around the cut and the
issue is likely to be which of the many buds do you keep and which buds to you rub off. Leave a lot if you are headed
toward a broom style with an elm. Keep just two if you want a new trunk with a single side branch. It is possible to
purchase stumped trident maples online and these can lead to trees with quite dramatic taper in a short period of time.
While spring is the optimal time for making stump cuts, I have also done it successfully with a lovely maple in
my yard that deer decided to use for rubbing the felt off their antlers. The tree was girdled and the top of it quickly
dried to a crisp. I cut it back to a stump and sealed the wound with cut paste. In the following spring, it pushed many
new branches around the cut and is now a nice bonsai.
You have been told that conifers cannot be cut back beyond the last green, so they should not be candidates for
stumping. Nonetheless, I have successfully stumped a white pine. It was two inch diameter and was cut back to 4
inches tall. Rather than pushing new branches around the cut like deciduous, the new branches pushed out of the bark
all around the trunk in a two inch band starting from the cut. There were far too many branches, but they were all
allowed to grow until the tree gets over the shock.
2. Pruning Ornamental Trees and Shrubs, Michael Dana and Philip Carpenter, Department of Horticulture, Purdue
Figure 2: Three-cut pruning. The initial cut (A) should
be an undercut to protect the bark on the branch. The
second cut (B) removes the branch taking the strain off
the joint. An arborist will tell you to make the third cut
at (C) but that will leave an unsightly but healthy wound.
Cutting flush at (D) will be more difficult to heal, but
will leave a better looking tree in the end.
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A B C
Figure 1: Pruning twigs. A) is pruned to far above the twig; B) is a
double cut for bonsai where the initial diagonal cut left a point above the
bud which was cut off in a second cut; C) is the cut recommended by an