Shohin vs. Standard Soil

[DrTolhur]

I've seen some sources offering shohin-specific soil, where the difference is largely in particle size compared to standard bonsai soil. Is there a need for smaller trees to have smaller soil? It intuitively makes sense to me for mame vs. imperial, so it seems like there must be some kind of transition point where you want to start considering a smaller soil mix. How do you know what size of soil particles you may need for one tree over another? Is it just by tree size, or other factors too?

 

[0soyoung]

It makes no sense to me. The working part of every root is at the tip. A few mm back is where the cell wall of individual epidermal cells becomes greatly extended to form the microscopic hair roots. This is where the overwhelming majority of the volume of water and mineral nutrients are adsorbed. The rest of the root is effectively just plumbing.

I have trees in 1 inch pots and various other sizes ranging upwards to 15+ gallon plastic nursery pots. I the same substrate for all. I set mini/mame pots on moist sand (shifted fines) bed or nest them inside larger pots of substrate during the summer. If you use smaller grained substrate you simply drown them (I.e., create anoxic conditions).

 

[Bnana]

It doesn't make sense from the perspective of the root, but it does when you think about the pot.
A small pot means that everything is close to the edge/surface so diffusion of oxygen is easier. On the other hand drying out is a bigger issue. So the trade of between openness and water holding capacity is different.
So for a small pot a slightly smaller partical might be better than for a very big pot. But in practice I wouldn't bother.

 

[Brian Van Fleet]

Smaller particle size allows a greater volume of soil in the pot, resulting in more water retention.
It helps to create wider margin of error when dealing with shohin trees.

 

[Colorado]

Yes I absolutely use different participle size for Shohin.

It would be absurd to use the same particle size for a mame tree versus an XL tree.

For some of the larger trees, such as a large ponderosa, the soil mix is screened to particle sizes 1/8”-1/4.” I would never use 1/4” particles for Shohin! You could only fit a few particles in the container! Lol.

For Shohin I leave in the 1/16” and screen out above 1/8”, but the majority of the mix ends up being closer to the 1/16”.

 

[Julio-Rufo]

Yes, they need smaller particle size as Colorado explained above.

The reason is not about margin of error when dealing with them but to achieve a finer root system that allows us to achieve smaller leaves (or needles) and finer ramification. When you use the smaller size akadama, the roots will start breaking down and splitting those smaller particles, achieving a much finer root system which will be reflected in a much finer ramification. That is the only way you can achieve the fantastic scale reduction you see in the good Japanese shohins. If you keep using the same size you would use for a bigger bonsai, it will be very hard to achieve a finer ramification and smaller leaves or almost impossible.

 

[penumbra]

I am in the margin of error group as a result of trial and error.

 

[Bnana]

finer root system that allows us to achieve smaller leaves

This is claimed very often but is there any evidence (e.g. scientific paper) showing that finer roots result in smaller leaves?
I don't have a clue how that would work physiologically.

 

[Julio-Rufo]

This is claimed very often but is there any evidence (e.g. scientific paper) showing that finer roots result in smaller leaves?
I don't have a clue how that would work physiologically.

No, I do not have a scientific paper.

How I understand it is as follows:

Thicker particles will produce coarser roots, (e.g. when doing air layers), coarser roots will provide a lot of (unrestrained) energy to the tree and its canopy. If you use finer particles you are forcing the tree to produce finer roots, creating a denser root system in a smaller amount of time that you would need if you use coarser substrate. The aim, when having a shohin or small bonsai in the container, is to restrain its growth. A more compacted root system will also restrict the growth of the upper canopy (producing smaller twigs, leaves, etc).

As I say, this is how I understand it, and I might be wrong!

 

[Tree Bender]

This is claimed very often but is there any evidence (e.g. scientific paper) showing that finer roots result in smaller leaves?
I don't have a clue how that would work physiologically.

How I understand this is that more water retention causes growth to slow, while less water retention causes more vigor. This is because there is more oxygen and less water. Obviously with less water retention you have to water more, but that means a higher rate of cycling between water and oxygen which is ideal for fast root growth. Ryan Neil is a proponent of angling the pot for trees that are not in good health, in order to increase water drainage. I think that finer root growth is a result of the smaller particle size, but really the smaller leaves and internodes results from the slowed growth and vigor of the bonsai, along with other refinement factors like increased branches that the tree is pushing its energy to. You can change the amount of water retention by particle size or particle type (akadama percentage).

I could be totally wrong as well, I am no expert. This is just my understanding from reading a lot of online material. Here’s a helpful article: https://bonsaitonight.com/2021/03/07/what-kind-of-soil-should-i-use-for-my-bonsai/

 

[0soyoung]

Finer grains mean

• lower air-filled-porosity
• higher saturation zone

Introductory soil physics

Questions about soil physics come up all the time and I find that I repeat myself a lot on this topic. I'm going to try and write a reference for folks to refer to on this topic. I'm expressly NOT going to offer you any advice on what soil you should use in your garden, whether you should use...

www.bonsainut.com

 

[Shogun610]

Shohin I’ve been sieving and using 1/16-1/8th grain size for akadama, 1/8 pumice or lava since they will give you more porosity and drainage with smaller grain Akadama that has higher water holding capacity. Helps on a hot day water won’t evaporate because of smaller grain sizes.

 

[JudyB]

I have always used the finer grained shohin soil, with great developmental results, and less drying stress in heat of summer. Plus it looks more in scale to the small tree in a small pot.

 

[Bnana]

No, I do not have a scientific paper.

How I understand it is as follows:

Thicker particles will produce coarser roots, (e.g. when doing air layers), coarser roots will provide a lot of (unrestrained) energy to the tree and its canopy. If you use finer particles you are forcing the tree to produce finer roots, creating a denser root system in a smaller amount of time that you would need if you use coarser substrate. The aim, when having a shohin or small bonsai in the container, is to restrain its growth. A more compacted root system will also restrict the growth of the upper canopy (producing smaller twigs, leaves, etc).

As I say, this is how I understand it, and I might be wrong!

I understand that finer material can result in finer roots but how would that affect branch structure and leaves? Restricting growth you do by pruning, not by having poor roots (and fine roots are more effective in nutrient uptake in the same volume). Reducing growth and pruning can result in fine branches, that I understand but that is independent of root structure.

I do agree it does sound kind of logic that finer roots will result in finer branches. It has a pseudo-logical ring to it. But once I start to think about it it doesn't make sense to me. It does sound like a false dogma.

 

[Julio-Rufo]

I understand that finer material can result in finer roots but how would that affect branch structure and leaves? Restricting growth you do by pruning, not by having poor roots (and fine roots are more effective in nutrient uptake in the same volume). Reducing growth and pruning can result in fine branches, that I understand but that is independent of root structure.

I do agree it does sound kind of logic that finer roots will result in finer branches. It has a pseudo-logical ring to it. But once I start to think about it it doesn't make sense to me. It does sound like a false dogma.

It is not only pruning but developing a mature root system (not a poor one, quite the opposite).

Check here, minute 2:50, I think it makes sense:

 

[Bnana]

I mentioned poor roots as I understand that a lack of nutrients can restricts the aboveground growth. So poor roots can result in smaller leaves and short internodes, that mechanism I understand. But that is not what you want. Refined roots do not function poorly so that can't be the mechanism here.

Peter Warren just repeats the dogma. Not a word about how a mature rootball in shorter internodes and a more mature crown. I can't come up with a mechanism.