How big can Maples be Grown in a Box?

[dbonsaiw]

I repotted a maple this fall that has never been cut and put it in a 14X14X3.5" wooden box. It's pushing 6 feet tall, but is still pretty thin. Base of the trunk is about 1.2" above the nebari (about 2" at the flare) and I think I'd like to continue growing the trunk. I used some thick gauged wire to secure the tree to the box as it would fall over otherwise. If I decide to continue growing it, should I put it in a larger nursery pot/in the ground or can I continue to grow it in the box? It's growing in a mix of 40% calcined clay, 40% pumice and 20% pine bark with some added peat moss (not even sure why I added that at this point). I included a pic if that matters (the box was sitting on the frame of another box to drain).

I will eventually cut this one down pretty far, leaving only a few inches and have a few styling options in mind. It has a nice root system and even some nebari started. I cut a substantial amount of roots off at the repotting (including the tap root) and still left more than was probably needed. Probably left about an 8" diameter root ball with lots of radial roots (the type that grows in potting soil, not the really fine roots).

 

[Dav4]

One trick to increasing overall growth with a containerized tree is to allow the roots to escape into the ground for a year or two, but that means you'll have to stay on top of the roots to prevent the nebari from becoming lopsided as one or two roots take over. Another option is to consider a ground layer of the containerized trunk once it's approaching the size you're shooting for. In ground growing gets the fastest but coarsest results. Regardless of the path you choose, the tree will need it's roots to be managed every few years.

 

[dbonsaiw]

Thank you. It seems the message you sent shows up differently on my email than here. This thread seems to be missing "Since you re-potted this fall, I'm assuming you didn't really work the roots in a meaningful way?" When I removed the tree from the pot it had a pretty large roots system. I turned the tree sideways and sawed off sections of the roots twice (two nice root cakes). I basically bare rooted it, cut off the tap root, downward growing roots and roots that were larger than others. The few other times I've done this with trees I could literally count the roots left. This one still looked like a bowl of spaghetti.

I like the idea of allowing the roots to escape and will noodle over how to doctor the box to accomplish this. Any ideas? The box has a ton of large holes on the bottom covered by a screen. Perhaps some of these can be opened to allow the roots to run. I'm a little hesitant to drill holes in the sides with the tree in there.

 

[Dav4]

Thank you. It seems the message you sent shows up differently on my email than here. This thread seems to be missing "Since you re-potted this fall, I'm assuming you didn't really work the roots in a meaningful way?" When I removed the tree from the pot it had a pretty large roots system. I turned the tree sideways and sawed off sections of the roots twice (two nice root cakes). I basically bare rooted it, cut off the tap root, downward growing roots and roots that were larger than others. The few other times I've done this with trees I could literally count the roots left. This one still looked like a bowl of spaghetti.

I like the idea of allowing the roots to escape and will noodle over how to doctor the box to accomplish this. Any ideas? The box has a ton of large holes on the bottom covered by a screen. Perhaps some of these can be opened to allow the roots to run. I'm a little hesitant to drill holes in the sides with the tree in there.

I misread your post as I was doing about 5 things at the same time on my computer, then saw that you actually had done a fair amount of root work... hence the changes to my post. As far as what to do to allow the roots to escape, simply placing the pot on the ground will usually do the trick. Fwiw, 2 years of unfettered growth in a maple can lead to some serious root thickening that may, during the next re-pot, cause irreversible damage to the drainage screens most folks install in a grow box- you've been warned .

 

[dbonsaiw]

Much appreciated. I will view the screens as disposable and replace them before they are ruined.

 

[parhamr]

The “only” limits are 1: how much foliage can be supported by those roots (without you having to water too frequently) and 2: how much canopy can be grown before it falls over all the time.

You could probably get two or three good years of canopy development out of the current roots.

I’ve had luck with 16" square (outer dimension; 3.5" deep) grow boxes as sufficient to support pretty large trees in development. I’ve had some trees in 21" square grow boxes but the difference was small. Those trees could certainly grow larger and had more weight preventing them from toppling over. It’s not like I got 2x the growth from them, however.

In general I think you’re close. Heavy feeding and bulking up will get you where you want to go

 

[River's Edge]

I repotted a maple this fall that has never been cut and put it in a 14X14X3.5" wooden box. It's pushing 6 feet tall, but is still pretty thin. Base of the trunk is about 1.2" above the nebari (about 2" at the flare) and I think I'd like to continue growing the trunk. I used some thick gauged wire to secure the tree to the box as it would fall over otherwise. If I decide to continue growing it, should I put it in a larger nursery pot/in the ground or can I continue to grow it in the box? It's growing in a mix of 40% calcined clay, 40% pumice and 20% pine bark with some added peat moss (not even sure why I added that at this point). I included a pic if that matters (the box was sitting on the frame of another box to drain).

I will eventually cut this one down pretty far, leaving only a few inches and have a few styling options in mind. It has a nice root system and even some nebari started. I cut a substantial amount of roots off at the repotting (including the tap root) and still left more than was probably needed. Probably left about an 8" diameter root ball with lots of radial roots (the type that grows in potting soil, not the really fine roots).

I am using 15 1/2 by 15 1/2 by 5 1/2 Anderson Flats to grow out maples. They need repotting every third year, plus the roots escape and run through the mesh bottom into the ground. I trim those once in late spring and again late summer by running a sharp knife across the bottom of the Anderson flat. If I did not do this they would be anchored through the gravel base into the ground. I prefer to be able to change their position to avoid too much direct sunlight during the hotter part of the summer. So this allows me to have them portable if I keep the escaping roots under control as I go. This also prevents a few from thickening much more than the others. As they get some size it is a good idea to add some granite grit to the mix for weight. They can reach 10 or 12 feet pretty quickly, particularly the tridents. The wind can then help build the base as long as the mix is heavy enough to provide a stable base. The wider container also helps, I do not use the full depth, probably 3 1/2 to 4 inch at most during development. I do keep the nebari covered during development.

Note: this is the largest size I use. This is the final transition after a grow box sized 13 by 13 by 6. They typically have a two inch base before transfer to the larger Anderson flat. I mention this only as a guide. The larger boxes have the advantage of not having to repot the trees so frequently.

 

[Shibui]

Many of you are already aware that I stopped growing tall trunks many years ago. I get much better results from repeated chops. Better taper, better trunk shape, better nebari and much faster final refinement stages because the larger initial chops are already partly healed.

 

[Potawatomi13]

Basically until box falls over in wind. Also depends on size of box.