markyscott
Imperial Masterpiece
Back to the original question - do you use an inorganic substrate or one with organics included and why?
I generally avoid questions like this as the responses tend to be quite loaded and the discourse degenerates very quickly. But, I'll put in my 2 cents because I think your question was genuine and I have a lot of respect for BVF. And because when people have problems with trees, I often see that they are planted in less than optimal soil. I think that the issue is that the trees can become much more difficult to care for as the soil mix departs from ideal. And our choices are limited because we grow our trees in shallow containers. When you plant your trees in a pot just a few inches deep, it presents a unique horticultural challenge which is why bonsai soil tends to look a lot different than regular potting soil. In deep pots (and the earth) a lot of things work fine and it's easy to find a soil mix (regular potting soil, for instance) that will give you optimal growing conditions. In a shallow pot, the ideal conditions are much harder to achieve.
The two most important physical properties of a potting mix are:
So what factors impact AFP?
So what about organics and inorganics? Inorganics:
So what do I use? First, you have to know that I have no plants in nursery containers - all are in bonsai pots or in shallow training pots. Second, you have to know that I live in Houston - it's high humidity (around eleventy million percent) here and we generally do not have winter freezes. We have a 10 month growing season and get about 48" of rain per year - usually all in one day. All of my plants are potted in inorganics - Boon mix. 1/2-3/8" particle size for maples and pines. 3/8-1/4" for most other plants (including bald cypress). I've been growing them in this medium for about 7 years. Before that I used various combinations of turface, haydite, and pine bark. I don't use that any more.
Why do I use it?
I generally avoid questions like this as the responses tend to be quite loaded and the discourse degenerates very quickly. But, I'll put in my 2 cents because I think your question was genuine and I have a lot of respect for BVF. And because when people have problems with trees, I often see that they are planted in less than optimal soil. I think that the issue is that the trees can become much more difficult to care for as the soil mix departs from ideal. And our choices are limited because we grow our trees in shallow containers. When you plant your trees in a pot just a few inches deep, it presents a unique horticultural challenge which is why bonsai soil tends to look a lot different than regular potting soil. In deep pots (and the earth) a lot of things work fine and it's easy to find a soil mix (regular potting soil, for instance) that will give you optimal growing conditions. In a shallow pot, the ideal conditions are much harder to achieve.
The two most important physical properties of a potting mix are:
- Air-filled porosity (the percentage of a potting volume that is occupied by the air after irrigation), and
- Water holding capacity (the percentage of a volume of potting mix that is occupied by water after irrigation).
So what factors impact AFP?
- Grain shape - rounded particles have lower porosity, angular fragments have higher porosity. Higher porosity tends to mean higher AFP and lower water-holding capacity.
- Grain size - porosity is not strongly affected by particle size, but the size of the pore space is. As you increase the grain size, the porosity remains the same, but the AFP increases and the water-holding capacity goes down.
- Sorting - a uniform grain size has a high porosity, high AFP, and lower water-holding capacity.
- Height of the container - the same soil in a deep pot has a lower AFP than in a shallow pot
So what about organics and inorganics? Inorganics:
- Tend to be larger particles. So they tend to have better drainage and higher AFP, thus maintaining an open, oxygen-rich structure.
- Tend to not break down as easily. So they add stability
- Tend to have a low CEC. So you must fertilize more offend, but you have much more control as to when the plants have access to fertilizer and when they don't. Limiting access to fertilizer is very important for maintaining more developed trees.
- Tend to have high CEC. So you don't have to fertilize as often, but you have less control on limiting access to fertilizer if you want.
- Tends to improve the microbial environment.
- Tend to have good water retention.
- Are less stable than inorganic components - over time it will break down into fine particles that inhabit drainage.
- Can sometimes become water-phobic when they dry out and are difficult to wet again when this happens.
So what do I use? First, you have to know that I have no plants in nursery containers - all are in bonsai pots or in shallow training pots. Second, you have to know that I live in Houston - it's high humidity (around eleventy million percent) here and we generally do not have winter freezes. We have a 10 month growing season and get about 48" of rain per year - usually all in one day. All of my plants are potted in inorganics - Boon mix. 1/2-3/8" particle size for maples and pines. 3/8-1/4" for most other plants (including bald cypress). I've been growing them in this medium for about 7 years. Before that I used various combinations of turface, haydite, and pine bark. I don't use that any more.
Why do I use it?
- Because I've tried other mediums and I like the results better.
- Because I find the trees easier to care for in an inorganic mix. Watering, for instance, is much less of a mystery. When I have someone watch my trees when I'm out of town - I just tell them to water every tree every day. It used to be MUCH more complex instructions.
- Because many of the artists I look up to in the US, Europe, and Japan use it (or some variation of it) and have excellent trees proving that you do not need organics to grow great trees.
- Because I've measured the AFP and water-holding capacity for the medium in the size containers that I use and it falls within the optimum range. Other mediums I've used do not.
- Because I'm in complete control of when the trees have access to fertilizer and when they are not - organic mediums have high CEC and hold on to fertilizer much longer than I like. Holding on to fertilizer presents a problem for black pines, for instance, as I withhold it after decandling until the summer shoots harden off. This technique is much more problematic if you can't withhold fertilizer because your soil is loaded with organics.
- Because it's much easier to tweak your soil for the growing conditions you want to achieve. Have a deep cascade pot? Put a finer mixture on top. Want drier conditions for that pine? Use a coarser grained mix.
- Because inorganic soils are much more stable and less prone to soil collapse.
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