Growing boxes are training containers used to develop the root systems of bonsai.

At the risk of being burned as a heretic, let me just get this out of the way by saying that trees hate bonsai pots. At best, they tolerate the confines of the typical bonsai container and the relatively poor drainage it affords. It's true that a tree may thrive in a bonsai pot given perfect potting soil, judicious watering and frequent repotting, but what can be achieved in a growing box is amazing.



When I first started growing trees, I was under the assumption that I could put small trees into little bonsai pots and somehow develop larger trees with great root systems. It might work over time, but that is about the slowest and least effective way to go about it.

The main defects of the bonsai pot in terms of the root system are the following. Please note that some of these so called limitations are important in developing refinement of the branches and a dwarf character to the tree, so we have to take the bad with the good, but I'm digressing:

DRAWBACKS to the TYPICAL BONSAI POT:

• Limited soil volume constrains the growth of root system
• Limited surface area creates poor diffusion of air into soil
• Usually narrower front and rear vs. sides, which causes poor development of roots at those points
• Little drainage, usually through 1-4 coin-sized holes, which are easily clogged with roots and soil.
• Pot depth encourages roots to grow downward as opposed to outward
• Usually vitreous and air can't penetrate walls
• Notoriously expensive
• Heavy
• Fragile

Now let's consider an inexpensive wooden growing box such as the one pictured below.

• Here, we have an inexpensive container which can be built with several strips of drainage along its bottom to provide as much or as little drainage as required
• Can be made square or oblong to accommodate various root systems
• Shallow and broad, promotes radial roots
• Very inexpensive
• Relatively durable. Can last 3 years and be disposed of at that point.
• Wires, turnbuckles and ties can be attached anywhere

Gosh, growing boxes would be ideal if they weren't bulky and ugly. The question comes down to:

A. Do I want an ok looking tree in a nice pot today or
B. Do I want a great looking tree in 2 or three years?

My own answer to that question is to move in the direction of growing containers. I still keep a few trees in displayable condition in nice pots, but what excites me most are those growing boxes. When repotting time comes it's like opening a present!

Here's a tree just going in to its growing box, which was reused from another tree.

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This closeup shows a couple of roots that were loosely wired to separate them a bit. In the wooden growing box we could actually use tacks, screws or nails to peg each one in place.

A wooden growing box is made with two-by-four lumber sides and a bottom of fenceboards to construct an inexpensive growing container for this giant maple.

I'd hate to think what a pot this size would cost. The sides are approximately 30 inches long.

The final show pot would be a a glazed oval of approximately the same width but narrower front-to-rear.

Those of us with more experiance can only agree with you matt. I hope that some of our newer members will take your advice and start using growing boxes. If they do I am shure that they will soon find all of the advantages of the technique.
ripsgreentree

I am new at this so bear with me. Are growing boxes suppose to be larger than the pot you are eventually going to use? If so, how much bigger? Is there a formula or ratio for this? How soon should a tree go into a traing box? Sorry for so many questions, but I am curious.

Yes, they have more volume, but the biggest difference is in surface area.

If a "typical" bonsai pot might be:

width (side to side): 2/3 the height of the tree
depth (front to back): 1/2 the height of the tree
height: 1/4 the height of the tree

The growing box might be:

width and depth: closer dimensionally to the height of the tree:
Height is usually deeper than the bonsai pot, because the tree is not yet adapted to a very shallow pot, but if the tree is adapted, the growing box could be fairly shallow.

Regards,

Matt

Here are a couple more photographs of trees going into growing boxes. The first is a Acer palmatum that just came from the same sized box and had its roots pruned back

First the tree:

And now the box:

If you want perfect roots, the box is the quickest way to get there. Here is an Acer burgerianium (Trident maple). You can see the nice radial roots, and this box will let them explode! As the roots grow horizontally, they will pull the root base (nebari) along with them.

Matt: Today we assembled 150 wooden boxes of different dimensions from an 8 inch square for shohin to a 24 inch square for larger trees, all have a depth of 3 inch with full screen bottoms. These are for the first trees coming out of the field with finished roots and nebari, we will now start training branches. What fun we are having.
Ripsgreentree