I have Sharp's Pygmy Japanese maple that I want to let the trunk develop for a few years. I however, will not be able to put it in the ground at least not for a year or better. Currently the tree is maybe 14-16 inches tall with a 1/2 inch trunk.

I am curious about building a grow box to use when I repot it in the spring and using bonsai soil rather than an appropriate potting soil.

The reasons why:

Bonsai soil allows better drainage which then seems I could keep it in a bigger grow box so that outward growth of the roots can be aided for improved nebari.

I think it would be more aesthetically pleasing especially while sitting near my other trees.

I could be wrong but it seems I would also have some more control over feeding and watering of the tree.

Thanks!

toque wrote: I could be wrong but it seems I would also have some more control over feeding and watering of the tree.

I don't think you are wrong. Your plans sound solid. Indeed with planting in bonsai substrate comes the need to properly fertilize and water.
Also, I would consider not to build a too large grow box, but to build a new, larger one once it is needed.

Auk wrote: I would consider not to build a too large grow box, but to build a new, larger one once it is needed.

Auk, I keep reading this advice in good bonsai books, but the reason escapes me. What is the difference between one large box for many years, to many bigger and bigger boxes throughout the years?

Clicio wrote:

Auk wrote: I would consider not to build a too large grow box, but to build a new, larger one once it is needed.

Auk, I keep reading this advice in good bonsai books, but the reason escapes me. What is the difference between one large box for many years, to many bigger and bigger boxes throughout the years?

When the box is too big, you get problems with watering. The outer sides, where there are no roots yet, will stay too wet for too long.
You should build a box that is large enough for roots too develop, but not so large that the outer sides stay too wet.

When the tree gets root-bound, you build a bigger box. You continue to do that progressively, until you reach the required result.

I have also seen this, other than allowing better aeration to the roots what other benefits are there to the wooden box. I have been thinking of doing the same thing with both of my maples

Travi51 wrote: I have also seen this, other than allowing better aeration to the roots what other benefits are there to the wooden box. I have been thinking of doing the same thing with both of my maples

They can be cheap and it's easy to make them the right size.

As Auk already indicated, there are many reasons for using them: www.growingbonsai.net/why-a-growbox-for-bonsai/
and they are easy to build: www.growingbonsai.net/built-instructions-for-a-bonsai-growbox/