Why Do You Wire a Bonsai Tree?

Why to wire a bonsai treeI’ve noticed that some bonsai trees that are wrapped with wire and others aren’t. I wondered if the unwired ones used to be wired, or if the wired ones started off unwired but weren’t growing properly and needed some help. So here I’m looking at why you might need to wire a bonsai tree to help me to understand why I’m doing it.

So why do you wire a bonsai tree? One of the aims in bonsai is to create a miniature tree that looks like a full-sized tree when viewed from a distance. Wiring a bonsai tree lets you recreate the movement and shape of the full-sized tree, and it’s an important part of the art of bonsai.

There are lots of forces and factors that naturally produce the shape of a full-sized that are difficult to replicate in the miniature bonsai tree. Wiring lets us recreate the look of the fill sized tree and there are a number of things to consider.

When Should You Start Wiring Your Bonsai Tree?

By “when to start” I’m thinking more of the stage in the life of the tree when you start to wire tree rather than the time year that you would do it.

As the young tree develops from a sapling the classic bonsai tree shape can start to be achieved with careful pruning. The desired effect is for the trunk to be thick at the bottom, tapering evenly as you move upwards into the branches. This make the bonsai resemble a full-sized tree viewed from a distance.

Careful wiring enables you to introduce the appearance of movement into the bonsai tree. Before starting to wire your tree some decisions need to be made about the final design, or style, of the tree. So, the placement of the wiring will differ depending on whether the tree is intended for an upright or slanted style, for example.

Wiring lets you apply forces in various directions to the growing sapling, and this force can be maintained by leaving the wiring in place. Opinions seem to vary about when to start wiring bonsai.

In my experience, which is still quite limited, the best time to start training the tree with wire is when the trunk and branches have been established but can still be bent fairly easily. At this stage they can be bent a little and return to their original shape when let go.

This lets you hold the trunk or branch in the position you want while you apply the wire. The wire then holds the tree in the shape you want.

As the tree grows the trunk and branches develop “secondary thickening”, which is a “woody” layer around the outside layer of the trunk and branches. The “new wood” thickens the trunk and branches and gradually hardens as lignin is produced.

This secondary thickening supports the structure of the tree, and holds the trunk and branches in the position you chose with the wiring.

What Type of Wire Should You Use?

The main requirements for bonsai wire are that it is thick enough to hold the trunk and branches in the desired position as the tree grows, that it won’t damage the bark of the tree, and that is can be repositioned or removed easily if required.

The two main options for bonsai wire seem to be anodized aluminum and annealed copper. You probably know what aluminium and copper are, but what about the anodized and annealed parts?

Anodizing applies an outer oxide covering to the aluminium, which is a bit like rust on iron. With aluminium this oxide covering helps the aluminium become more resistant to corrosion. Annealing of the copper wire seems to make it more useful for bonsai as it bends easily the first time (when you are wrapping it around the tree) then holds it’s shape from that point on.

The type of tree seems to help determine which type of wire to use: aluminium for deciduous trees and copper for evergreen conifer types of tree. This seems to be because the harder copper wire can hold the more flexible conifer trunks and branches more tightly. People also seem to recommend the softer aluminium wire for beginners.

How Thick Should the Wire Be?

Bonsai wire is available in various thicknesses, or gauges. I’ve been trying different thicknesses of wire and the thing that seems to determine how thick the wire needs to be is whether it seems to be holding the branch or not.

If the wire is too thin it’s not going to be able to exert enough force. If it’s too thick you might not be able to bend it to the required shape and not damage the tree.

A rule of thumb seems to be that for annealed copper wire the thickness should be around a quarter to a third of the thickness of the branch you are working with. For anodises aluminium wire it needs to be little thicker, around a third to a half of the diameter of the branch. This may be just a suggestion, but it appears to makes sense.

How Much Strain Should You Apply When Wiring?

Wire is applied carefully around the tree limbs, starting at the bottom of the trunk and working up around the branches as high as desired. Wire before bending, then you can apply the pressure gradually and the wire will hold the tree in place.

It seems sensible to apply a little pressure at first, then as the tree limb starts to take shape you can gradually bend it further over time. The idea I have in mind is the way dental braces move your teeth gradually a little at a time. This softly-softly approach might be unnecessary, but I’m always worried about breaking the trunk or branches.

Can Wiring Damage the Bonsai Tree?

Clearly, there is a risk that wiring your bonsai tree could damage the trunk or branches. It’s important to avoid concentrating the pressure onto one point, and this can be done by applying the bending force as evenly as possible around the branch.

Wrapping the trunk and branches with bonsai raffia prior to wiring can help to avoid damaging the tree. Wetting the raffia makes it more pliable, and it can be squeezed flat for wrapping around the branches. The wiring can then be applied over the raffia covering.

The tree can also become damaged when removing the wire. This often happens if you try to unwind the wire from the trunk or branches. As you unwind the wire you can cut into the bark without being aware of it, and this can split or even strip away areas of the bark.

To avoid damaging the tree when removing the wire it is usually best to cut the wire at convenient points and remove it in small sections. This means that the wire cannot be reused, but the extra cost is worthwhile since it helps to reduce the risk of having to deal with a damaged tree.

How Long Should You Leave the Wire on For?

Now we’ve looked at issues relating to the removal of the wire, you might be wondering how long you should leave the wire on the tree. This usually depends on the type of bonsai tree you are dealing with.

If you search on the various bonsai forums you will see a lot of different opinions on this, so I have tried to distill the various points of view into something that works for me.

If you remove the wire before the thickening and hardening of the trunk and branches (that I mentioned above) has fixed the reshaping produced by the wiring then the tree may not stay in the shape you wanted.

Something to watch out for is the wire “biting” in to the bark. This is due the the trunk and/or branches thickening, and it an cause damage to the bark. This will happen faster in the spring and early summer, since it is caused by the bonsai tree growing.

The types of timescale mentioned when people are talking about the length time that you need to leave the wire on the tree is usually months or years. You will need to keep and eye on the tree as it develops and adjust or remove the wiring as you think necessary. Remember, bonsai is usually thought of as an art rather than a science.

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