Size of Grow Box

dbonsaiw

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I have been reading various threads that touch on the ideal size of a grow box and was wondering why bigger isn't always better from the perspective of quicker growth. As I understand it, ground growing produces the quickest growth because the roots have plenty of room to run, but one runs the risks of having their nebari get away from them due to the rapid growth. Alternatively, using a shallower grow box will allow one to control the nebari better, but at the expense of slower growth. Putting availability of space and cost of soil aside, wouldn't we get the best of both worlds if we used an incredibly long and wide box that was shallow?

I've heard people say things along the lines of "the box is too big for the tree" and I'm not sure what that even means. All things being equal, why not plant a very young and small tree in a 50"X50"X4" grow box filled with the best bonsai soil for the tree/climate to grow it out?
 

TwilightTrees

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The bigger the grow box, the more difficult it is to keep it aerated. So if I use big grow box for awkward long yamadori roots, I will make a lot of holes in the side of the growbox to be sure all corners of the box get oxygen.
 

Wood

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My understanding is that a lot of it comes down to water/oxygen balance. Due to soil physics, the capillary action of the bottom layer of media in a pot holds on to water and doesn't drain it completely. If there are no roots in that zone to take up the water, evaporation is the only way for the water to disperse. A grow box that it slightly larger than the root ball forces roots to fill the space seeking more water, which makes the soil dry out faster. The rapid water/dry cycle helps to speed up the growth of the tree

That bottom layer issue doesn't exist in the ground. Water will continue percolating downward in soil until it hits the water table. Roots in the earth will continue to extend searching for more water

Still relatively new at this, so this is my interpretation of the research I've read, not something I've experienced firsthand
 
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rockm

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I have been reading various threads that touch on the ideal size of a grow box and was wondering why bigger isn't always better from the perspective of quicker growth. As I understand it, ground growing produces the quickest growth because the roots have plenty of room to run, but one runs the risks of having their nebari get away from them due to the rapid growth. Alternatively, using a shallower grow box will allow one to control the nebari better, but at the expense of slower growth. Putting availability of space and cost of soil aside, wouldn't we get the best of both worlds if we used an incredibly long and wide box that was shallow?

I've heard people say things along the lines of "the box is too big for the tree" and I'm not sure what that even means. All things being equal, why not plant a very young and small tree in a 50"X50"X4" grow box filled with the best bonsai soil for the tree/climate to grow it out?
Bigger is WORSE because of soil volume and root mass.

Boils down to the larger volume of soil in a big pot takess longer to dry out than a smaller volume of soil. That doesn't sound bad right?

BUT consider it from the roots' point of view. The soil directly around the tree trunk and roots is what newly collected roots will use. They will "colonize" and establish themselves in that area first. The remaining soil won't really be used--depending on how oversized the box is--for some time, perhaps years.

That means the soil immediately around growing parts of the root mass will use more and more water, leaving unused areas untapped and constantly wetter than the colonized areas. As time passes, that situation is multiplied because new roots become more and more reluctant to pass into unused, wet portions of the soil. Roots don't like to pass between different soil types...Given enough time, it can also kill roots off.

Rule of thumb is to use the SMALLEST possible box for newly collected trees. It speeds up root development and can help prevent root rot.

SHallow pots are good --UP TO A POINT. Shallow pots don't drain very well, heat up and cool down more quickly and to more extremes than a "regular" pot.
 

Wulfskaar

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I think it's about balance. You'll probably want to repot every couple years or so and root prune, so the roots won't have a chance at running away too far. Also, the cost of the soil may keep you from having what would be a lot of soil being unused or barely used by the roots. You want it big enough for the tree to stretch it's feet, but any more is a waste.
 

dbonsaiw

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The answer appears to be that more unoccupied soil equates to more water retention and the issues that flow from that. This makes perfect sense, especially if we are using a high percentage of organics in the soil. Does this analysis change at all if what is being used is purely inorganic? I've never had the opportunity to observe pumice, for example, in a 50X50X3.5" grow box into which a tiny tree is planted. I would have assumed that the unoccupied portions of the soil wouldn't retain water for very long and, therefore, there wouldnt be such a market difference between the occupied and unoccupied portions.
 

rockm

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The answer appears to be that more unoccupied soil equates to more water retention and the issues that flow from that. This makes perfect sense, especially if we are using a high percentage of organics in the soil. Does this analysis change at all if what is being used is purely inorganic? I've never had the opportunity to observe pumice, for example, in a 50X50X3.5" grow box into which a tiny tree is planted. I would have assumed that the unoccupied portions of the soil wouldn't retain water for very long and, therefore, there wouldnt be such a market difference between the occupied and unoccupied portions.
Not really an difference. Smaller is better regardless of soil type. Just look at some of the odd shaped planting boxes made for newly collected junipers/pines
 
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The answer is: know your climate and know your tree.
I collected the above tree and it recovered rather quickly with this oversized grow box. Simply put this tree needed help generating roots near the nebari and this method has proven results. If you use the correct potting medium, watering practices and watching the tree you will be successful. I wouldn't do this ↑ on all tree species, but for the junipers here this works.
 

River's Edge

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The grow box should be sized for the purpose it is intended for. Species, Condition and developmental goals.
It depends, newly collected tree, tree in need of rejuvenation.
Depth is variable by species and stage of development the root ball is at.
Maples can benefit from a shallower box due to the type of root ball and nebari desired for most maple designs. This is not true for conifers generally and they benefit from a bit deeper grow box as they do a bit deeper Bonsai Pot.
In this and many other aspects of Bonsai "one size does not fit all"
It must also suit the particular climate and maintenance routine it will be subjected to in order to function effectively.
For all the above reasons the best one can do is choose a reasonable size for a starting point and adjust for your circumstances as you gain experience with the outcomes.
There are good general guidelines that have been p[ublished and discussed. A good discussion on this topic is found in Michael Hagedoorn's latest book " Bonsai Heresy"
For collected trees I build for 1 extra inch on the outside of the root ball and 1 inch deeper than the existing root ball to start with and downsize as development progresses.
For deciduous development I choose a 5 inch depth to begin with and cover the roots by 1/2 to 1 inch. So the box is not always full but the roots are covered as the tree develops.
For conifers I choose a six inch depth and keep the roots covered in development. Once again the box is not always full.
Length and width for either deciduous or conifer that is based on the stage of development and condition but is rarely more than an inch or two wider than needed at the time of transfer.
If a grow box is larger than needed I may use boards to fill up some of the space rather than take time to build a new one. Anderson Flats are easy to adapt this way. Particularly the deeper style as it can be used for either deciduous or conifers by the depth it is filled to.
 

dbonsaiw

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The grow box should be sized for the purpose it is intended for.
I will size my boxes according to the discussion above. Hate to beat a dead horse. What I don’t seem to then understand is why growing in the ground doesn’t raise the same concerns. For example, the area immediately surrounding the root ball will necessarily be dryer than the ground further away. Yet the roots aren’t “scared away” by this different wetness in soil. I’m not arguing with anything said here - I’m just trying to understand what about the box changed the soil dynamics. It’s not like there will be a water table in a box filled with inorganic material and this should dry fairly quickly. Also, I would have assumed that the mere act of watering the bonsai soil would aerate the soil as the water drains.
 

River's Edge

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I’m just trying to understand what about the box changed the soil dynamics
Important question, the moisture available is concentrated in a smaller area and thus it has a very important flushing effect. This keeps a fresher supply of air and removes waste products from the confined area. Assuming that one waters throughly and then waits until more watering is needed. The same flushing effect is less in ground planting normally. unless it is very sandy, or coarse in makeup. So essentially we re taking about creating a healthier environment.
The benefits to ground growing as I understand it are associated with a more stable temperature zone for the roots. Also less tendency to dry quickly or stay too wet for extended periods, as moisture can migrate.
The container will only be as effective as the care routine applied to it and is more reactive to moisture loss and wind desiccation. Just some thoughts associated with your question.
 

Wulfskaar

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I will size my boxes according to the discussion above. Hate to beat a dead horse. What I don’t seem to then understand is why growing in the ground doesn’t raise the same concerns. For example, the area immediately surrounding the root ball will necessarily be dryer than the ground further away. Yet the roots aren’t “scared away” by this different wetness in soil. I’m not arguing with anything said here - I’m just trying to understand what about the box changed the soil dynamics. It’s not like there will be a water table in a box filled with inorganic material and this should dry fairly quickly. Also, I would have assumed that the mere act of watering the bonsai soil would aerate the soil as the water drains.
I don't remember all the details, but I recently read a debate about grow boxes vs ground growing. What I got out of it was that there are pros and cons to each, but having it in a box does allow it to be moved, turned, put on a table for pruning/wiring, etc. You also get a bit more control over the tree as a whole since it is easily repotted and you have control over the soil. Ground growing, to me, seems like what you want to do if you're just going to let it grow for a few years in order to let it get much thicker.
 

dbonsaiw

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What I got out of it was that there are pros and cons to each
Indeed. The hypothetical 50X50X5" box was an exercise to see if the best of both worlds could be obtained and, if not, to better understand why. If I'm understanding River's Edge correctly, the use of a grow box basically creates its own little ecosystem and, perhaps more importantly, gives rise to soil dynamics that are considerably different than what exists in ground. In short, the soil dynamics of the ground allow for more consistency in terms of temperature, moisture and air. Using a larger box will obviously give the roots more room to run, similar to in ground growing. The trade-off for this additional space in the box, however, is a loss of a more essential soil characteristic - consistency in terms of temperature, moisture and air throughout the box. In fact, this lack of consistency actually undercuts the reason one would use a larger box in the first place as the roots may very well not run given the difference in soil conditions throughout the box. Accordingly, the suggestion seems to be size the box larger, but not disproportionately larger, than the root system we are working with. With the roots occupying a large portion of the soil, consistency is achieved, and the roots can still run, albeit less than in ground (allowing for better nebari production etc.). Every 1-2 years the roots would be pruned back (or it could be up-potted).
 

Dav4

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I'll agree with all the points above concerning over-potting being bad for root health, but would also mention that a large (20+ inches per side), lumber built box full of soil weighs a substantial amount and is ungainly to move regardless of weight. Unless you never have to move your trees/winterize them, an oversized box can be very difficult to move by yourself, and this is another check for building appropriately sized boxes to fit the existing root system. Fwiw, I use wooden boxes mainly because they breath well/drain well and warm the soil quickly which are all beneficial for root growth and subsequent training...

This box is 22.5" x 14.5" and made of 6" X 1" decking. Filled with akadama and the tree, the box easily weighs 40 pounds.
IMG_6495.jpg
 

dbonsaiw

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This box is 22.5" x 14.5" and made of 6" X 1" decking. Filled with akadama and the tree, the box easily weighs 40 pounds.
First off, really cool tree. How large would you say the root system was when planted in this box? Did it fill 1/4, 1/2, 3/4 etc?

I can attest to the difficulty of moving some of these around. Even if the weight isn't overly excessive to lift, the size of the box makes it unruly for one person to move around. I have some taller trees growing out in 14X14 boxes and have taken a tree to the face on multiple occasions while moving them myself.

(Speaking of which, I was shitting a brick last night watching these taller trees sway in intense winds all night long - my son and I had an over/under on when the tree would snap or just come right out of the box. I'm using heavy gauge wire to secure the tree by its trunk to the box and it seems to have held up. I always underestimate how prepared trees are for mother nature -they obviously did not snap. With any luck, these trees will wake up in the next few weeks and I can start doing some work on them in the summer. Winter in NY is simply way too long).
 

rockm

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I will size my boxes according to the discussion above. Hate to beat a dead horse. What I don’t seem to then understand is why growing in the ground doesn’t raise the same concerns. For example, the area immediately surrounding the root ball will necessarily be dryer than the ground further away. Yet the roots aren’t “scared away” by this different wetness in soil. I’m not arguing with anything said here - I’m just trying to understand what about the box changed the soil dynamics. It’s not like there will be a water table in a box filled with inorganic material and this should dry fairly quickly. Also, I would have assumed that the mere act of watering the bonsai soil would aerate the soil as the water drains.
Because the ground has comparatively infinite drainage space. Containers are containers and water acts differently in them--perched water tables...confined space for drainage--there is nowhere for water to drain off to, besides the drain holes you provide. . In the ground, Roots have free range to "look" for water for the most part in areas that are most amenable to them. Not true in a container where roots are forced to adapt to what's given them. The ground has no limits, sides, bottom, etc. Land areas that don't drain all that well are swamps because they're CONTAINED---think about it...
 

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