How long should wire stay on a bonsai?

Until the branch holds its position on its own — usually one growing season. Deciduous trees set fast, often in 2–4 months; junipers and other conifers take 6–12. Check every 4–6 weeks from application: the moment bark starts swelling around the wire, it comes off.

The wire is biting into the bark — what do I do?

Take it off today. Cut the wire away in small pieces with wire cutters rather than unwinding it — unwinding levers against the branch and snaps more wood than the wire ever saved. Shallow bite marks on a vigorous deciduous tree grow out in a season or two; deep spirals are permanent scars.

Can I reuse bonsai wire?

Aluminum, yes — straighten it by hand and it's ready to work again. Copper, no: annealed copper hardens as you bend it (that stiffening is exactly why it holds so well), so once it's been shaped, it won't apply cleanly a second time. Budget accordingly — copper is a consumable.

When should I wire a bonsai?

Late winter for deciduous trees — bare branches are easy to see and spring growth locks the new position in. Conifers are most flexible in late fall and winter. Avoid wiring right after repotting or heavy pruning; one intervention at a time. The wiring guide covers timing tree by tree.

Bonsailist

The tool bench

Bonsai wire gauge selector — the right wire for the bend

Tell us the branch, get the gauge. No more guessing at the wire rack.

Wire gauge selectorthe 1/3 rule

Branch diameter (in)

Wire material

What are you wiring?

How far are you bending it?

enter the branch's diameter — the gauge appears here

After the math

How to use this result

Cut a length about one and a half times the branch, anchor it two turns back on the trunk or a parent branch, and wrap at roughly 45 degrees — snug to the bark, never strangling it. Then bend slowly, with both hands, supporting the branch from outside the curve.

The test of the gauge is the bend itself: if the branch springs back, the wire is too thin — size up or add a second wire alongside the first. If you're denting bark just by wrapping, it's too thick. One gauge can wire two branches of similar thickness, which is the tidiest way to anchor both.

Full technique, turn by turn, lives in the wiring guide.

No black box

How the selector works

One bench rule, applied in the open:

The 1/3 rule: wire diameter ≈ one third of the branch's diameter, for anodized aluminum. A 6 mm branch wants 2 mm wire.
Copper: annealed copper work-hardens as you apply it, so it holds roughly the next size up's worth of branch — we drop one step down the ladder.
Trunks: stiffer wood on a longer lever — we go one size up from the branch answer.
The ladder: results snap to the standard sizes — 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, and 6 mm — rounding up, because wire that's slightly too strong beats wire that doesn't hold.
Past 6 mm: we stop recommending single wires. Two wires laid side by side or a padded guy wire moves heavy wood with less risk of snapping it.

Our take on metal: start with aluminum. It's cheaper, forgiving to apply, and kind to thin bark — copper earns its place once you're styling junipers and pines seriously.

The care sheet version

Wire gauge quick reference

Branch diameter	Aluminum	Copper
3 mm (1/8″)	1 mm	1 mm
6 mm (1/4″)	2 mm	1.5 mm
9 mm (3/8″)	3 mm	2.5 mm
12 mm (1/2″)	4 mm	3.5 mm
15 mm (5/8″)	5 mm	4 mm
18 mm (3/4″)	6 mm	5 mm
Over 18 mm (3/4″)	Double wires or a padded guy wire — single wire stops being the right tool.

Before you buy

What a 100 g roll actually holds

Bonsai wire sells by weight, not length — and the length difference between materials surprises people. Thick copper rolls are short: 100 g of 4 mm copper is under a meter of wire.

Gauge	Aluminum per 100 g	Copper per 100 g
1 mm	47 m (154 ft)	14 m (47 ft)
1.5 mm	21 m (69 ft)	6.3 m (21 ft)
2 mm	12 m (39 ft)	3.6 m (12 ft)
2.5 mm	7.5 m (25 ft)	2.3 m (7.5 ft)
3 mm	5.2 m (17 ft)	1.6 m (5.2 ft)
4 mm	2.9 m (9.7 ft)	0.9 m (2.9 ft)
5 mm	1.9 m (6.2 ft)	0.6 m (1.9 ft)
6 mm	1.3 m (4.3 ft)	0.4 m (1.3 ft)

No black box here either: length = 100 g ÷ (density × cross-section). Aluminum runs 2.70 g/cm³, copper 8.96 g/cm³ — that 3.3× density gap is the whole table. A practical starter kit is 100 g each of 1.5, 2, and 3 mm aluminum; buy copper by the job, not the shelf.

Timing

When to wire, by tree type

Deciduous (maple, elm, hornbeam)
Late winter before buds move, or early summer once new leaves harden. Branches thicken fast in spring — check wire every 3–4 weeks or it bites.
Junipers & most conifers
Late fall through winter is the classic window: growth is slow, so the wire stays put longer. Expect 6–12 months to set.
Pines
Fall and winter, after the year's candle work is done. Winter-wired pines set over the following season.
Indoor tropicals (ficus, jade)
Any month — indoor growth doesn't pause. Fast growers like ficus swallow wire in 6–8 weeks, so check early and often.

Growers argue about the edges of every window — the part nobody argues about is checking monthly once the wire is on.

Bonsai wire FAQ