Mastering the skill of wiring will give you much more scope when creating or refining your bonsai. You can change the direction of the branches or trunk, wire an upward branch into the horizontal, turn a branch on a young tree downward to simulate age, or maintain and refine new growth. These articles and others throughout the site show the various ways in which wiring can enhance a bonsai style.
The Best Time to Wire
Although in theory you can wire at any time, some seasons are better than others. It is easiest to wire deciduous trees just before the leaf buds unfold in spring, or before they become dormant in the fall. Leaf-cut trees like maples and elms are best wired just after you remove the leaves. Wire evergreens at any time, but conifers are best done when dormant from late fall to early spring.
How Long to Leave the Wire
Check regularly that wire is not biting into the growing bark as the tree continues to thicken, or long-term damage may be caused. When the limb is firmly set in its new position, remove the wire completely. How soon depends on the species of tree, the age and quality of the wood, and the thickness of the branches or trunk: a flexible young branch will hold its new position more quickly than resistant older wood. As a rule, leave wiring three to six months on deciduous trees, about twice as long as on evergreens.
How to Remove the Wire
You can unwind the wire, but there is less risk of damaging the tree if you cut it away in little pieces. Wire left on too long will bite into the tree: this must be unwound very carefully, retracing its original direction. Paint any deeply cut bark with a wound sealant.
Some branches may slowly revert to their former position after the wire is removed, and will need rewiring in the original direction; if, however, the bark is badly scarred, wire in the opposite direction.
Shaping the Tree
This slanting-style bonsai was last wired five years ago. Branches that were trained in a downward direction have begun to lift toward the light once more. It will be rewired (far right) to refine the shape by adjusting the direction and growth pattern of the branches.
Cut the wire away carefully in little pieces, rather than unwinding it, to prevent any damage to the bark of the tree.
Wire Too Tight
The branch of this conifer is swelling because the wire has been left on too long. As a result, scarring has occurred.
Scarring to the branch caused by wire shows clearly when the wire is removed. The wound may not grow out for years.
Copper and aluminum are the most common types of bonsai wire. Copper is less obtrusive, because it has an attractive color, and is strong enough to be used in smaller gauges than aluminum. Copper wire is best for conifers, because it supports the flexible wood firmly. It does have the disadvantage of hardening over time, so it may scar the bark when it is removed. It also needs to be made more pliable by annealing. Sometimes you can buy it pre-annealed; if not, non-annealed wire is easy to find. Heat it over a low-temperature fire until it glows a bright cherry red; if overheated, it becomes brittle. Cool it slowly. It can be re-used after re-annealing.
The lighter, softer aluminum wire is better for deciduous trees, as it is less* likely to damage the bark. It can also be re-used. It is, however, not so strong as copper wire, so you need to use it in a thicker gauge. Ordinary aluminum wire is a bright, silvery color that does not blend with the tree; it is better to use aluminum wire treated with a dull coppery finish. This is readily available in specialist shops, and is the most commonly used type.
Wire comes in many different thicknesses, so match the gauge carefully to the size and vigor of the trunk or branch. Generally, choose a gauge between one-sixth and one-third of the diameter of the wood, but you should also consider the age and resistance of the wood, and how much you need to bend it when shaping the bonsai.
Beginners find it takes much time and practice to master the technique of wiring. It is very important to learn first how to wire a bonsai specimen accurately and neatly; once you have mastered this, you will soon gain speed. Do not underestimate the value of proper wiring: it is not possible to shape a tree well with careless wiring.
Other methods of shaping (tying branches down with strings or wires, tying them to canes, or suspending weights from them) are used less, because they are less effective.
Before starting to wire, collect together enough wire in the gauges you think you will need. You should have wire cutters strong enough to cut the wire. Pliers will help you to hold the wire easily and to finish off the ends. Cut your wire a third as long again as the branch or trunk you intend to wire, so that you can wind it at a 45-degree angle, the best angle for effective wiring.
To protect the bark on heavy branches that you may have to bend drastically, you will find raffia useful. Wind it around the branches before wiring. If you are wiring delicate or soft twigs, it is often best to wrap the wire with strips of paper before using it.