Chapter 37 Wiring

Note: this essay incorporates information from these previously published stories and resources.

Bonsai Basic Teaching Program, by Dennis Makishima, Golden State Bonsai Federation, 12/05/2008
Bonsai Teachers’ Guide, by Bonsai Clubs International, http://bonsai-bci.com
Some Basic “Rules” of Bonsai Wiring, by John Ong, originally published in 1994 and reprinted November 2006 in the Piedmont NC Bonsai Association newsletter.

37.1 Choosing Appropriate Wire

Most bonsai wiring is done with 1.5 mm, 2 mm, 3 mm, 4 mm, or 5 mm diameter anodized brown aluminum wire. Solid copper wire is less popular because a) it is much more expensive than aluminum wire, and b) it becomes stiffer after it is bent, making it harder to bend smoothly. Some stylists recycle copper wire salvaged from electrical installations by burning off the insulation in a fire. This is fine as long as the user is careful not to bend the copper wire several times. Do not use uncoated steel wire, because it will rust and stain branches.

37.2 Basic Wiring Technique

Deciduous trees usually are wired in early spring, before the buds begin to open, or in autumn, just prior to dormancy. Evergreens can be wired almost any time they are flexible but should not be wired when the tree is dormant or nearly so. Don’t wire a tree right after root pruning or transplanting.

Let a tree dry down somewhat before wiring and/or bending it. The branches will be more pliable and less likely to break or scar.

Generally the largest wire used to bend a branch should be no more than 1/4 to 1/3 the diameter of the branch at its smallest point. That said, use the smallest gauge of wire that can bend the branch successfully.

Tip: One way to test what gauge wire is needed is to test it on a branch on a yard tree that is about the same diameter and stiffness. Wrap a wire that is 1/5 the size of the branch and try to bend it as desired. If it does not hold in place, go up one size in wire and try again. Once you can keep a branch bent on a tree in the yard, switch over and use the same size wire on the bonsai tree.

To wrap a branch, cut a length of wire 3-4 times longer than the branch to be bent. Ideally, one piece of wire can be wrapped around two adjacent branches, anchoring it in place. If this is not possible, wrap the wire 2-3 times around the trunk before continuing it out onto the branch.

Tip: Do not wire every branch on a tree simultaneously. Wire and bend just the trunk, or branch that most needs it first. After the first branch is shaped, start wiring and bending smaller secondary branches.

Wrap the wire around the branch in a spiral with the wire at a 50-60^o angle to the long axis of the branch. Work slowly. Be careful not to knock off or injure emerging buds or green branches. Press each wire coil firmly against the branch or trunk with your thumb when wrapping (or unwrapping) the next coil. This prevents the wire from slipping and damaging the bark/cambium. Don’t pull the wire too tightly though; it should just rest on the surface, and not bite into or dent the branch.

Don’t cross the wires. If more than one wire is needed, lay the strands side by side.

Wrap the branch fully before bending it. A properly wired branch can be bent gradually over several days or even weeks. It is not necessary to bend a wired branch immediately or all at once.

Thoroughly water the wired tree, and move it to a shaded location for a few days to recover. Return the tree to its normal location, and check the wires weekly to make sure they are not cutting into the bark.

Normally wires can be removed after 6-12 weeks. If the branch has not set yet its new shape, rewire the branch but wrap the wire in the opposite direction.

Fig. #: Basic wiring. Link to original image

37.3 Guy Staking and Wiring

Before wire was used to bend branches, bonsai artists used stakes and string or rope to pull branches into place. Guy stakes and guy wires can be used the same way. I cut V-shaped guy stakes from branches I have pruned off other trees or find lying in the yard. Unlike branch wire, 1.5 mm or 2 mm suffices for most guy wires. I also recycle old wire that I have removed from bent branches; the kinks and bends will not affect the wire’s tensile strength.

Guy wires must be anchored in holes in the wall of the training pot, or by passing them under a large root. The point where the wire crosses the branch being pulled down should be well padded to keep the wire from cutting into the bark. I use pieces of landscape cloth folded in quarters; they do not hold water so do not create a spot for rot to take hold.

Guy staking and wiring. Image 1. The lower branch on this winged elm is being held in place by a guy stake that I cut from another handy tree branch. Image 2. Guy wires wrapped around the main trunk of a 36-inch tall cedar; this tree is one of three in the tray scene. These wires wrap around the base of the pot and keep the tree from toppling out while the roots become established. Image 3. This cryptomeria is wired into its pot using insulated single-strand copper wire. In this case I have used the anchor wire as a point for attaching an enameled aluminum guy wire that is pulling down one of the branches to a horizontal position. The aluminum wire is looped because I moved this branch a little at a time over several weeks. The loop shows how much distance the branch moved over time from its original upward-pointing position. Image 4. This Arizona cedar has a side branch that I am converting into a new apex. The branch was bent up then wrapped with wire to hold it on the old trunk (which will be removed later.) the end of the new lateral branch is being pulled down to the horizontal by a guy wire extending down to the base of the tree. Since the tree will never be shown with these wires in place, I did not bother to cut off the extra piece sticking out towards the tip of the bent branch. Original photos by Dan Johnson.

37.4 Splint Wiring Technique

Some tree branches are too stiff to bend easily, or have brittle wood that is likely to break rather than bend. These tough bends can be made more easily by splinting the branch first.

A heavy wire or group of several smaller wires approximately 1/3 the diameter and three times longer than the area of the branch to be bent is wrapped in floral tape or raffia to provide padding. The padded wire is folded in half to make a U shape that fits around the branch to be bent. Then the bend is bent up 90^o, to make a wire splint that fits on either side of the area to be bent.

The wire splint is placed around the branch, with one strand on what will be the concave side of the bend, and the other strand on the convex side. Then the splint is wrapped with a long strip of nylon stocking to anchor it in place. The nylon should be snug but not tight, and the wires ends should not be bound down.

Fig. #: Splint wiring. Link to original image

Once the splint is anchored, the branch is slowly bent to the desired shape. The wires should slide slightly as the branch bends. When the bend is close to final position, it is wrapped more snugly with another strip of nylon stocking. Do not bind down the cut ends of the wire splint; they could cut into the bark. Instead, tuck the end of the nylon wrapping under the wires. This keeps the bark protected, and allows the nylon wrap to be adjusted as needed.

Splints are used to move heavier branches, so often need to be left in place for longer than spiral-wrapped branch wires. Check regularly that the wrapping is not digging into the bark, and re-wrap as necessary.

37.5 Trunk Bending and Wiring

If a tree trunk has too little movement, it can be bent by a combination of staking and wiring. This must be done carefully because it combines wiring with a lever action, making it much easier to damage the cambium or break the trunk.

Cut 3-4 wooden stakes that are the same diameter as the area of the trunk to be bent, and several inches longer than the tree is tall, including the pot.
Wrap the middle third of one stake with raffia or lengths of nylon hose to pad the contact point with the trunk.
Loosely wire the padded part of the stake to the middle of the trunk. The stake should be parallel to the trunk.
Using the stake as a hand-hold and lever, bend the trunk to create a flowing curve. The stake should be on the insider of the bend.
When the curve looks right, push the lower end of the stake into the soil to anchor the lower end and help hold the trunk at an angle.
Continue bending areas of the trunk using padded stakes to support the inner face of the curves. Once the trunk has the flow desired, secure the ends of the stakes either by pushing them into the soil or anchoring them by wiring them more tightly.
Watch the wire wrappings carefully. With the added pressure, the wire can bite into the trunk more easily than the branches.

Fig. #: Trunk bending. Link to original image