So, I am doing a fairly unusual bonsai tree.

An avocado.

I planted him from seed about anywhere from 4-6 months ago, I can't quite remember when exactly I planted him.

But, he is growing extremely well he is within the range of 16"-18" tall now.

However, he is still green 100%, he isn't thick tan wood yet. Still very malleable and soft green.

So, I am wondering when I should start root / stem pruning.

Should I start stem pruning to make him smaller and fill out his lower layers?
And should I start root pruning when he is only 4-6 months old?

Thanks in advance.

Here are a few picture of him for you guys:

Two issues:
1-) Their leaves are almost impossible to be reduced in size to make an harmonious bonsai.
2-) It is still very young to be pruned, chopped or wired, isn't it?

Camamoow wrote: So, I am doing a fairly unusual bonsai tree.

An avocado

Avocado is not suitable for bonsai at all.

Mind giving me reason as to why?

Many bonsai guides say any tree will do.

1. I don't care how 'harmonious' it looks, as long as it's technically 'bonsai'-ed.
2. Thats what I am here asking about... I am a beginner.

Camamoow wrote: 1. I don't care how 'harmonious' it looks, as long as it's technically 'bonsai'-ed.

Technically, it will never become a real bonsai.

2. Thats what I am here asking about... I am a beginner.

This is discussed very often here. Not every plant in a pot can be called a bonsai.

So, why specifically is Avocado not suitable
?

Camamoow wrote: So, why specifically is Avocado not suitable
?

Because it will never look like a miniature tree.

Camamoow wrote: So, why specifically is Avocado not suitable?

As Clicio said, they have large leaves that are hard to reduce in size.
They also grow very fast which might cause trouble.
As they are not used for bonsai, there isn't much (any) information that I can find on whether they respond to bonsai techniques, but it is likely that they do not.