In order to create good bonsai, often it is needed to perform some type of wiring on your tree. After all, we are working with trees that would like to grow up, into a large tree, and do not always agree with our ideal placement of branches which is more out than upwards.
Guy wires for bonsai development
A downside of wiring the bonsai by coiling the wire around a branch is that within a fairly short amount of time (Typically a few months to a year) the branch has started to grow around the wire (The wire is biting in) and the wire needs to be removed to avoid long-term visible scarring. Especially for some species (Notably Larch and Spruce) this is not long enough to get the branches set. But also for thicker branches on other species this is often not enough time.
Talking about thicker branches: These will need quite heavy wire, and technique needs to be perfect to get the bends to stick.
Using Guy Wires for bonsai
An alternative is the use of guy wires. Guy wires are a great bonsai technique to set branches. It took me a while to realize the potential of these. Instead of coiling the wire around the branch, you take a very thin wire. Attach it to the branch you want to bend. Here you ensure proper padding between the branch and the wire. I use pieces of rubber tubing. Ensure you have a very loose loop that will not restrict the branch when growing. In the direction of the intended bend, find a solid anchor point to attach the wire to. I often use a yin, but also another branch, a screw, root, the pot or wiring will work. Now you can position the branch in the direction you want, and use the wire to keep it in place.
In the example pictures I have used a stainless-steel screw to attach the wires. This juniper had been wired 3 times already, and every time the branches come back up after unwiring. So here I decided I will leave the guy wires on for several years. After removing the wires, I will remove the screw. The small hole should close with time.
When to use it
Guy wires only work in the direction that the branch is pulled. So I use them to pull a branch in a certain direction.
You can use it on many species. Some species, such as Japanese maples, scar very easily. Using a guy wire to put the main branches at the right angle, and regular coiling for the side-branches reduced the risk of wire biting in on larger branches that need long to set.
When not to use it
This bonsai technique only works for placing branches in 1 direction. So it is not good to build curvy branches. I typically do the shaping of branches with coiling, sometimes at a very young age such as baby bending. Positioning / setting the branch angle for thicker branches I do with guy wires.
To keep in mind
When you wire a tree by coiling, quite intense bends are being put in the branch. This causes internal trauma, to which the tree responds with additional growth in order to repair the damage. With guy-wires less trauma is caused, and the bend is usually placed over much longer stretch of branch. As such, fixing a branch in place takes disproportionally longer.