Often considered the most difficult training technique, wiring is used to bend the trunk and branches of a tree into the shape you would like your bonsai to take. Beginners can learn to judge tension in different sized branches, and the various ways of securing wire, by first practicing on a small branch from an ordinary tree or shrub. Never rush. Deciding the shape your tree will take is a lifetime decision, so be sure to examine all angles and possibilities.
Copper wire, though expensive, is most suitable for wiring a bonsai-to-be such as the juniper above, because it remains soft. Galvanized iron or plastic coated wire may be used, but they tend to look rather ugly and detract from your tree. Remember, the larger coniferous trees will be wearing their wires for 12 – 18 months, so please take care in choosing the best "look" for your bonsai.
The same juniper, after wiring.
How To Begin:
When first starting to wire your tree or shrub, you will find that gentle bending of a branch before wiring will increase its flexibility and give you an idea of the correct strength of wire. What you are looking for is a wire that will give you a tension slightly more than the tension of the branch. Tender-barked trees, such as maples, should be trained with paper-wrapped wire to protect the bark.
When To Wire:
Deciduous trees should be wired after their leaves have matured, in early summer, and the wires removed in autumn to avoid wounding the bark.
Coniferous trees should be wired during the winter months, since they take considerably longer to become fixed in position. All trees should be protected from hot sun and heavy rain for a month after wiring.
Wiring A Bonsai Tree:
Begin wiring from the base of the trunk, anchoring the wire in the soil. You may need two wires to hold the trunk in position. After securing the base of the trunk, proceed to the main, and then the smaller branches, ending with the highest twigs. Wires should be wound at about 45 degrees to the line of the branch. Gauge the tension carefully, as tight wiring will cut into the bark, and loose wiring will slip.
Dealing With Breaks
Even if you are very careful, you may bend a branch to its breaking point while wiring. If the break is simply a fracture with the broken part still partially attached, you have a chance of saving the branch. Very gently ease the broken part into place, carefully fitting both ends of thebreak together. Wrap the break with garden tape or raffia and tie it securely, but not too tightly. Within several months, the fractured branch tissue may knit together.
If the break is complete or the ends fail to unite, you have several choices. You can cut the broken branch back to where side branches grow out from it, or you can cut it back to its point of origin.
Care After Wiring:
To help your bonsai recover from the trauma of wiring, keep it out of direct sunlight for several days. It’s also a good idea to keep it sheltered from wind for several weeks. Water the plant routinely, giving the foliage a daily sprinkling.
Removing The Wire
To give wired branches a good chance to grow into their new positions, leave wires in place for a full growing season. Then, in early autumn, remove them to avoid any constriction during the next growth phase. If wires are left in plce too long, the bark will show unsightly spiral scars for years. With stiff copper wire, it is best to cut it carefully from branches to avoid inflicting damage by uncoiling. Aluminum wire can be uncoiled, starting at the outmost end and carefully uncoiling toward the anchor end.
If wired branches still need more coaxing to achieve the desired positions, they cn be rewired at the appropriate time for another year of training. When you rewire a branch, vary the wire position from that of the previous year.