Sooner or later all bonsai growers need to bend parts of a bonsai. Whether the bend is in the trunk or just moving a branch slightly there is always some fear that the tree will break instead of bending the way you want it.
Here are some tips on how to get the bends without the trauma.
First a word of warning: Each species has different wood. Some are quite flexible and can bend easily. Others are more brittle and will break much more easily. Junipers and pines are quite flexible. Maples and quite a few of our Aussie natives have much harder wood and break easily when you try to bend them. You’ll also find that younger wood is far easier to bend than older wood even in the same plant so, wherever possible make bends when the tree is young or on newer branches.
The most common way to bend bonsai is to apply wire and then just bend the trunk into the desired position. There is a limit to how far the wood will bend before breaking. Just bend slowly, feeling and looking for signs that you’ve reached the limit.
Small cracks have started to open up on the trunk. Time to stop bending – for now.
To make more severe bends bonsai growers wrap the part tightly before bending. The wrapping helps spread the forces and holds the wood together while it is bent. Even if the wood does split a little the wrapping holds it all in place and the tree will heal as it grows. By the time you unwrap there is usually little sign of the breakage. Traditionally bonsai growers wrap branches with wet raffia but anything strong and flexible can be used. In this example I have used PVC electrical tape but I’ve also seen strips of bicycle inner tube, twine and hessian tape used successfully.
After wrapping the trunk apply a wire then bend into position.
If the wood is just too thick or stiff to bend with the wire you have available or you want even more extreme bends, try splitting the trunk/branch. This allows the 2 pieces of wood to move more freely and it can be bent much easier. The best tool to do this are purpose built trunk splitters. In this example the trunk is still fairly thin so I was only able to split it once.
Thicker wood can be split into 4 or 6 pieces to make even really stiff wood quite pliable.
Bind the split part with tape, raffia, etc as in the previous example then add a wire as normal before making the bends. You should find that the split allows the wood to bend far more easily.
In most cases, using any method, you’ll find that it is easier to bend if you twist the trunk/branch as you bend it. Twisting brings new wood onto the outside of the bend, allowing the stresses to be shared more evenly.
If you still can’t get enough bend, leave the tree to rest for a week or so. After resting you’ll find that the wood has relaxed and you’ll be able to bend even further without breaking it. Here’s the first example with wire only. After a week I was able to bend the lower trunk even further.
Sometimes a single wire is not enough to hold the desired bend. A thicker wire may do the trick but sometimes it is better to add a second wire. 2 wires, evenly spaced will help spread the stress and you can get even more bend without cracking the wood. Bonsai growers also use tie wires to help hold extreme bends until they set in place.
If the worst does happen and you hear the dreaded cracking sound or see cracks appear in the bark stop bending immediately. Hopefully the crack is small and only part way through. Just cover the broken area with sealing paste and leave it alone. Usually the tree will heal up naturally with little or no problem. If the crack is large – more than 1/2 of the wood – bend it back a little so the edges are closer together, seal the area and cross your fingers. In most cases the trees we use are quite good at healing and will survive.
If you look closely at the picture just above. You may be able to see where the juniper has split – just where each of the branches are growing. These cracks run along the grain of the wood and will heal quite easily without endangering the tree so I have not even bothered to seal them.
Something to note: Previously broken areas that have healed up are always much weaker than surrounding wood. If you try to bend that area again it is likely to break in the same spot even more easily than before. If you still really need to bend it, make the bends nearby rather than trying to bend that spot again.
Occasionally the wood will snap completely. That’s called an ‘Oh Bugger!’ moment. There’s not much you can do to rectify the problem. Walk away for a while to calm your nerves then come back and take a good look at what you have left and look for another possible style for your tree. Part of being a bonsai grower is making do with what you have.
There’s a whole host of factors that influence how long it will be before you can take the wires off – the species, how well the tree has grown, age of the wood, etc. Younger wood will often be set in place after just a few weeks but older wood may need an entire season or sometimes even longer to set. I usually leave wires on for the entire growing season but you will need to check wired trees regularly. If you can see the wood bulging around the wire it is time to take it off immediately. If the tree starts to straighten up apply fresh wire, bend it back into place and leave it for another few months.