One of the unique aspects of bonsai practice is the use of wire to shape trees. Let’s delve into the reasons for wiring bonsai, the typical types and sizes of wire, and how to apply wire to trees.

Those new to the hobby are sometimes intimidated by the prospect of wiring bonsai. While this technique takes a bit of practice, wiring is a skill all practitioners need to learn.

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Why Wire?

Wiring is used to guide the growth and structure of bonsai to achieve an aesthetically pleasing shape and style. Almost all bonsai need wiring at some point in their lives in order to reach their full potential.

Other techniques used in the hobby to guide and shape growth include guy wires, clamps and braces. However, wiring prevails as the go-to method that bonsai practitioners employ to improve the style of their trees.

When to Perform Bonsai Wiring

There are no hard rules against wiring trees whenever the hobbyist chooses. However, depending on the type tree, some times work better than others. Once wire is applied to a tree, it remains either until the restyled wood sets (hardens) into the new position, or until the growing tree branch is on the verge of becoming damaged from the ever-tightening wire.

The best time to wire deciduous trees is in late winter or early spring, prior to bud break. The bare branches not only make the actual job of wiring easier; they also allow the practitioner to better see and adjust the tree’s structure. Deciduous trees generally set the new position within the same growing season, typically taking from just a few weeks to six months to harden.

Most hobbyists consider late summer into fall and winter the optimum time to wire conifer bonsai. These species of trees tend to have brittle branches. Later in the year, once the tree is past its growth spurt and sap has started to wane, the branches become more flexible. Wires often remain on conifers eight to ten months, providing they don’t dig into the bark. Conifers sometimes need two or more successive wirings before branches retain the desired shape.

Some bonsai hobbyists avoid wiring tropical species, due to their tendency to have softer wood that grows rapidly. These types of trees can develop wire scars within just a few weeks of application if they are not closely monitored. 

Types of Bonsai Wire

The ideal bonsai wire should be pliable enough to wrap and bend easily, yet strong enough to hold the trunk or branch in place. 

Traditionally, bonsai practitioners have used annealed copper wire to shape their trees. “Annealing” is a process that subjects wire to very high temperatures. Annealing renders the wire flexible and easy to bend. Once the wire bends again – as in when wrapping it around a tree trunk or branch – it hardens once more. Over time, it also oxidizes, losing its coppery shine and becoming less noticeable on the tree.

More recently, anodized aluminum wire has become a popular alternative to copper. Anodization allows the application of color to the wire – generally an unobtrusive brown that helps blend with the color of tree bark. While the pliability of aluminum wire makes it easy to work with, aluminum is not as strong as copper and does not harden after bending. Therefore, it takes a thicker aluminum wire to do the same job as copper.

Selecting Bonsai Wire 

While either copper or aluminum can be used interchangeably, a general rule of thumb is to use aluminum wire for deciduous species and copper wire for conifers. Deciduous trees tend to bend easily and set into the new shape in one growing season. Conifers are more difficult to bend and take longer to set, so copper’s strength and hardness works well for these trees.

The range of wire sizes most commonly used in bonsai, are from 1mm to 5mm. Trunks and heavy branches on larger trees might require the heaviest gauge wire, however hobbyists use the finer thicknesses more frequently.

Aluminum wire in 1mm, 1.5mm, 2.5mm and 4 mm sizes makes a good starter set for those new to the hobby. Variety packs such as this 3-roll set work well for the smaller trees that beginners usually start with.

6 Steps to Successful Bonsai Wiring

Let’s break down the process of wiring, step by step, to make it easier for those new to the process.

Step 1: Choose the wire type and thickness

Knowing the best size wire to use for any application becomes easier with time and experience. The thickness used needs to be substantial enough to hold the desired shape, but not so big that it overwhelms. A traditional guideline for wire selection is to choose a thickness that is about one-third the thickness of the branch being wired. After selecting the wire, cut a length around one third longer than the length of the area you plan to wire.

Step 2: Anchor the wire

If you are wiring the trunk, anchor the wire by inserting one end deep into the soil. If you are wiring a branch, anchor the wire by wrapping it around the trunk or to an opposing branch. One commonly used technique is to wire two opposing branches with one length of wire. Anchor by wrapping the middle of the wire around the trunk, then use one of the sides to wrap each of the two branches.  When anchoring and wrapping, always avoid crossing one wire over top of another.

Step 3: Wrap the wire at a 45-degree angle

Aiming for 45 degrees ensures proper positioning of the wire for maximum strength and holding power. Wrap the wire flush with the branch, but not tight. Take care to avoid pinching and damaging foliage on the branches as you wrap. This is one reason why it works best to wire deciduous trees in early spring prior to bud break.

When you come to the end of a branch, cut off the excess wire. If the branch needs a stronger wire than what you have available, you can double-wire. The easiest way to do this is to double the length of the wire when you cut it, fold the length in half, and carefully wrap the tree with the two wires positioned side by side.

Be sure to apply all the wire you intend to use on the tree prior to moving to the next step.

Step 4: Bend the branches or trunk into the desired shape

Grasp the branch with both hands, holding your thumbs against the intended inflection point. Gently bend the branch, stopping right away if the wood shows signs of splitting. Brittle branches sometimes require bending in stages, allowing some time in between. 

Step 5: Check the tree regularly

It will take time for each branch to become set in the new position. During this period, it is important to check the tree often for signs that the wire is creating indentations in the bark. As the tree grows, the trunk and branches can thicken to the point where they start to grow around the wire. When this happens, it results in unsightly wire marks in the bark that permanently disfigure the tree. Avoid buying trees with wire scars, and guard against letting them occur in practice.

Step 6: Remove the wire 

Using bonsai wire cutters, snip the wire at short intervals. The blunt nose of this specialized tool allows you to safely position the cutter against the bark without damaging it. Lift the wire off a bit at a time, leaving the bark intact. Never remove wire by uncoiling it from a tree. This can break branches and severely damage the bonsai. 

After wire removal, it’s not uncommon to re-wire conifers right away. Because they set branches so slowly, it sometimes takes several successive wirings to achieve the desired shape. Most deciduous trees set much faster, so they can stay wire-free until the cycle starts over again with the arrival of late winter.

Check out other articles on our site for helpful beginners’ tips, including the posts about bonsai soil and watering bonsai .

We’ve covered the reasons for wiring bonsai and the types of wire used. We also explored how tree types differ when it comes to wiring and outlined the basic steps involved in wiring trees.