Wiring Bonsai — Aluminum & Copper Wire

Choosing wire. Use wire that is about 1/3 of the thickness of the branch you are about to train. When wiring thick branches, first soak raffia (palm fiber) in water and wrap it around the branches to protect them from damage during bending.

Technique. If wiring the entire tree, always start from the branches at the base of the trunk, then wire secondary branches after the primary ones. Wrap the wire at a 45-degree angle. Plan the direction carefully: placing it clockwise or counterclockwise affects the branch when bending — e.g. moving a branch down to the right with clockwise-coiled wire tightens it slightly, while counterclockwise loosens and loses support. Carefully line each new piece of wire with the wire already wrapped. Select a suitable size for each branch (you may use 2 mm for one branch and need 3 mm for the next). When bending a branch downwards the wire should come from below; when bending upwards it should come on top — this secures the wire and reduces the risk of splitting branches. Fertilize and water the bonsai properly, indoors or outdoors as suited to its type.

Applying to the trunk. Hold the wire firmly to the trunk's base with one hand and coil it at 45 degrees with the other, pushing the coiling hand upward after every turn so it follows the spiral up the trunk. Match the wire gauge to the trunk; when the trunk becomes too slim for the current wire, switch to a heavier strand, trailing the wider wire up for at least two turns before proceeding to the top. Embed the wire at 45 degrees about 2–3 inches into the soil at the base of the trunk, then wrap a compact 45-degree coil around the base, firmly and with no gaps. After bending the trunk, wait 3–4 months for the wire to set before removing it; remove sooner if the trunk begins to bite into the wire.

Aluminum wire. Softer than copper, so easier to use and re-usable. It must be properly anodized (an electrochemical process that thickens the natural oxide layer, making the surface more durable and corrosion-resistant). Downsides: low holding power, so you'll likely need a heavier gauge than copper, and in direct sunlight anodized aluminum takes on a bright silver hue some find unappealing. Wiring can be done year-round for most species, but early spring or late winter is recommended; late winter is best for deciduous plants. Wiring must not cut into the tree. Summer wiring is possible but foliage gets in the way, and the sap-rich cambium means drastic bends can separate the bark — though smaller branches harden in summer and are easier to wire. Autumn wiring is not advisable, as the trees are setting next year's foliage.

Copper wire. Naturally heavier and stronger than aluminum, so it holds thicker branches with a smaller diameter, and many find it more attractive and less visible. It does not change color over time. Downsides: harder to bend, needing a heavier gauge and more effort. Copper works excellently for conifers but may not suit tropical bonsai, as conifers grow much more slowly than fast-flourishing tropical varieties.

When to wire. Wire when the tree is young and healthy, after re-potting, and time it to the plant type. Deciduous trees: early spring, when new buds are on the limbs and structure is clear before leaves emerge. Coniferous trees: late autumn or early winter, when sap is lowest and branches most flexible. Do not wire a sick tree or weak branches (they may snap). Feed well-balanced fertilizer to strengthen the tree first, and avoid wiring a freshly watered plant — limbs are most flexible when slightly dehydrated. Quick rules: start at a tight angle as the wire emerges from the soil; wire at 45 degrees throughout; anchor branch wire around the trunk wire; use a smaller angle past a sharp bend for extra support; one wire may serve two branches of equal thickness; anchor around the trunk for balance; never wire branches of different thicknesses with the same wire; for a strong branch use two or three wires wound together.