Moving from nursery container to grow box. What size to build?

[Matt3839]

This coming spring I’m going to be moving a lot of trees to grow boxes and I’m a little unclear about what size to build.
the trees (Hinoki and cryptomeria) are coming out of nursery pots so I’ll be exposing nebari and doing some root pruning at the bottom after but still leaving native soil at first.

If I were to take a tree that’s in a 5 gallon container - assuming I prune some roots and expose nebari would I want to do a grow box maybe 2/3 of the volume? 1/2?

I know we’re a ways off from spring but I thought it would be a nice winter project and I have 7 or 8 boxes to make. And maybe able to get some free lumber from a construction site before it gets tossed so any guidance is very appreciated.

 

[Shibui]

What is the aim of transferring to grow boxes? 5 gallon container is already pretty big so either the trees are quite large or they will have plenty of room to grow in those pots.
Going down in size would assume your trees have finished growing and you're moving on to developing apex and branching by slowing growth?

I'm not sure there's any rule of thumb on sizing a development box. Appropriate size probably has less to do with the current container size and more about the current size of the tree, the species and what you want to achieve.

 

[Matt3839]

What is the aim of transferring to grow boxes? 5 gallon container is already pretty big so either the trees are quite large or they will have plenty of room to grow in those pots.
Going down in size would assume your trees have finished growing and you're moving on to developing apex and branching by slowing growth?

I'm not sure there's any rule of thumb on sizing a development box. Appropriate size probably has less to do with the current container size and more about the current size of the tree, the species and what you want to achieve.

So my main goals are:
A) transferring or at least partially transferring to a bonsai substrate
B) thicken trunk but not looking for gain in height.
C) create more fine roots
D) expose nebari on trees so I can start to think about design. So they’re going to need to be repotted anyways.



I’m pretty happy with the few trees I put into pond baskets when they arrived bare rooted, and so I’d like to also repot my other nursery stock stuff. But the pond baskets are too small I think, plus I do like the look of a wood grow box vs plastic

Hope that all helps. Open to thoughts!

 

[Shibui]

A, C and D are good reasons to transplant to new soil and will probably be facilitated by a smaller container.
Trees will grow in bonsai substrate, even in larger containers but transferring to bonsai substrate is only really important when moving to smaller containers. Doesn't matter so much in larger grow containers and can usually wait until development is done.
I have not noticed that different soil types or different containers have significant bearing on fine roots. My experience is that creating fine roots is best achieved through judicious root pruning.
Exposing nebari is a vital first step to design but we don't have to go full transplant to do that. Just raking off the surface soil is usually enough to get a good enough look at nebari.

I think B - thickening trunk but restricting height might be counterproductive unless you plan on a ver r r ry long project. Trunk thickening seems to be directly linked to growth - either apex or sacrifice branches. Smaller container will usually restrict growth of either or both which will normally result in less thickening. larger containers for thickening, smaller containers to restrict growth for developing better proportioned branching with closer internodes.

Unfortunately, we don't seem to be able to get everything we want all at the same time when growing trees.

Wood V plastic is also a valid reason but has no relevance on size.

I would be making boxes that are suit the size of the tree but are also convenient to house and to move. In La you won't need to overwinter but will probably need to rotate trees to get good all round growth. You'll also want to move then occasionally for trimming, styling, etc and may even want to take some to workshops, etc so make them manageable if possible.