What is the best soil mixes for conifers?

[Warlock]

Is this inorganic soil for all climates? Seems like the trees could use a bit of extra water retention when it is over 100 degees in Central/South Texas for whole summer..

 

[Adair M]

Inorganic soil prevents root rot.

If you need more water, water more frequently, or add a layer of orchid moss on top of the soil. Not IN the soil, on top, like a blanket.

 

[stu929]

Inorganic soil prevents root rot.

If you need more water, water more frequently, or add a layer of orchid moss on top of the soil. Not IN the soil, on top, like a blanket.

While I understand this is simple in concept what about vacations or someone who has to travel a lot for work? Would it be better to build in a little more water retention to add a buffer to avoid losing trees.

 

[mrcasey]

Hey guys. Hope i can use this thread for my question.
Well i am quite new in bonsai. Already read some therads about soil but didnt find info about pine burk mulch. Everybody says it has to be composted. How can i determine if it is or not if on the bag is not written. I am wondering what happen if i use normal pine bark mulch? What problems can show up. I add a picture of the much i found in local store. I gladly ask you for some explanations about that.
I would like to use pine bark and perlite for mugo pines.
Lime stone would be ok as inorganic component instead of granite?

For those who DO use organics in their mix, the most common objection to non-composted bark is that it causes some nitrogen lock up. According to Brent Walston though, the minor amount of lock up is completely mitigated by any normal fertilizer regimen.

I used to use pine bark, turface, and granite for all my trees. Then I read an article by Graham Potter who advised ditching all non porous aggregate. Potter claimed that all non porous aggregate just acts as a heat sink and absorbs no water or air. So I switched out the granite for perlite and have noticed lots more visual mycorrhizae around my pine roots. Does that mean that my trees are healthier? Possibly. It could also mean that the mycorrhizae prefer my new mix and the trees couldn't care less.

Just to be clear - I'm not saying that you should be using organics in your soil.

 

[Shibui]

Lime stone would be ok as inorganic component instead of granite?

Limestone is alkaline. I believe pines prefer slightly acid soils so swapping granite for limestone could be detrimental for some trees.
I have not used limestone as a major part of potting mix so just going on theory and many theoretical proposals have proved unfounded.

If you try this just do some test runs with smaller batches and dispensable trees just in case.

FYI there are many growers who use many different mixes for pines and other trees with good results.
My pines are growing quite happily in pine bark/coarse sand mix.

 

[Wires_Guy_wires]

So I switched out the granite for perlite and have noticed lots more visual mycorrhizae around my pine roots.

I added granite instead of removing it and got similar results; my pine soils are colonized within 3-4 months and I lost percolation entirely. I have fungus growing out of the pot holes and I can keep the pot upside down without losing soil because it's all caked up by the fungus.
This is happening in my wooden pots and in my terracotta pots, but not in the plastic pots.

This was may 2020, before the repot:

I think this type of fungal growth is mainly related with pot conditions (terracotta holds water and breathes) and the fact that only fungi can reach deep enough into these rocks to find nutrients. With organic soils, most of those nutrients are released by bacteria instead of fungi.

 

[mrcasey]

I added granite instead of removing it and got similar results; my pine soils are colonized within 3-4 months and I lost percolation entirely. I have fungus growing out of the pot holes and I can keep the pot upside down without losing soil because it's all caked up by the fungus.
This is happening in my wooden pots and in my terracotta pots, but not in the plastic pots.

This was may 2020, before the repot:

I think this type of fungal growth is mainly related with pot conditions (terracotta holds water and breathes) and the fact that only fungi can reach deep enough into these rocks to find nutrients. With organic soils, most of those nutrients are released by bacteria instead of fungi.

That really surprises me, but thanks for posting your opposite experience. Crushed granite is a lot more attractive than perlite, too.

 

[Jure_v]

While I understand this is simple in concept what about vacations or someone who has to travel a lot for work? Would it be better to build in a little more water retention to add a buffer to avoid losing trees.

That is what i was thinking.
Inorganic sounds better option but then you have to have time for watering a lot. And during vacation need someone reliable.

 

[Jure_v]

Limestone is alkaline. I believe pines prefer slightly acid soils so swapping granite for limestone could be detrimental for some trees.
I have not used limestone as a major part of potting mix so just going on theory and many theoretical proposals have proved unfounded.

If you try this just do some test runs with smaller batches and dispensable trees just in case.

FYI there are many growers who use many different mixes for pines and other trees with good results.
My pines are growing quite happily in pine bark/coarse sand mix.

Thanks. That sounds promising. So pine bark can be ok with some fertilizing to cover the loss of nitrogen.
Maybe i am not able to get crushed granite here so river gravel could be good replacement?

 

[Adair M]

The problem with using Crushed granite as a substrate is particle shape. It’s sharp and angular, not rounded. This means it can “pack”. Round particles of the same size can’t pack. There’s always air space in between particles. That air space assists with drainage, and allows oxygen exchange.

Pine bark particles are rather flat. They’ll stack up and also, “pack”.

Pumice and lava are more rounded, therefore they are superior bonsai substrates.

 

[stu929]

That is what i was thinking.
Inorganic sounds better option but then you have to have time for watering a lot. And during vacation need someone reliable.

I don't have anyone reliable locally which is why I asked.

 

[Leo in N E Illinois]

@Jure_v - limestone is NOT a good substitute for granite. Granite is primarily silica, and chemically inert. Limestone is primarily calcium carbonate, and reactive. Limestone will dissolve in cold water. Limestone will dissolve in weak acids. Limestone will make for an alkaline pH of soil media. Alkaline conditions are disliked by many species of trees. There are a few which require alkaline soils, but they are case by case.

More often the case, trees found in alkaline soils "merely tolerate" alkaline situations rather than "prefer" alkaline conditions. Generally especially for mapes, carpinus, and most "forest trees" avoid alkaline soils and limestone. Ideal soils are weakly acidic, in the pH 6.0 to 6.5 range. Some potting media are quite acidic, such as peat, some components as they break down can release weak acids, like bark. Designed mixes will sometimes have small amounts of limestone calibrated to counter these acidic effects of other components, but the limestone will be in small enough amounts to avoid creating and alkaline mix.

@Warlock & @stu929 - water retentive mixes. I have, do or did use a lot of organics in my mixes at one time or another to allow me to get away with watering once 3 days. This way I could take a long weekend or a short work trip without worrying about arranging "Watering Help". Or having to rely on an automated watering system.

Downside of adding bark or peat or other organics to mixes - you really have to be care to avoid watering too frequently. As the organics break down their water holding capacity will change, for example bark will initially hold a moderate amount of water. After 6 months of decomposing, the water held will increase. As the decomposition continues, suddenly the bark will hold less water.

As organics break down, they will fall apart into smaller and smaller particles. These smaller particles will settle into lower levels in the pot, sometimes clogging up air voids between particles making oxygen poor pockets, here roots in those pockets will die, and begin to rot, becoming an avenue for pathogenic microbes to get into the vascular system of the tree, causing one catastrophic rot or another.

So while organics in the mix will allow a long weekend, it requires much more careful watering to prevent the issues of overwatering. Also, the media will be dynamically evolving, so watering frequency will change not only with the weather but depending on the age of the mix.

A pure pumice, lava & akadama mix. Or a mix that is 100% inorganic, will not change much over time. So the only variable in watering is current weather conditions and size of tree to size of pot.

One option, is to over-pot to some degree, and continue to use an all inorganic, lava-pumice-akadama mix. A sufficiently large pot will allow a long weekend. The hazards of over-potting in a all mineral mix are not as severe as over-potting in an organic mix.

Better solution is to look into automatic watering systems. If you enjoy tinkering with gadgets, this is the ideal solution. more reliable than the neighbor kid or a relative. With some work, can be close to 100% fail safe.

 

[stu929]

@Jure_v - limestone is NOT a good substitute for granite. Granite is primarily silica, and chemically inert. Limestone is primarily calcium carbonate, and reactive. Limestone will dissolve in cold water. Limestone will dissolve in weak acids. Limestone will make for an alkaline pH of soil media. Alkaline conditions are disliked by many species of trees. There are a few which require alkaline soils, but they are case by case.

More often the case, trees found in alkaline soils "merely tolerate" alkaline situations rather than "prefer" alkaline conditions. Generally especially for mapes, carpinus, and most "forest trees" avoid alkaline soils and limestone. Ideal soils are weakly acidic, in the pH 6.0 to 6.5 range. Some potting media are quite acidic, such as peat, some components as they break down can release weak acids, like bark. Designed mixes will sometimes have small amounts of limestone calibrated to counter these acidic effects of other components, but the limestone will be in small enough amounts to avoid creating and alkaline mix.

@Warlock & @stu929 - water retentive mixes. I have, do or did use a lot of organics in my mixes at one time or another to allow me to get away with watering once 3 days. This way I could take a long weekend or a short work trip without worrying about arranging "Watering Help". Or having to rely on an automated watering system.

Downside of adding bark or peat or other organics to mixes - you really have to be care to avoid watering too frequently. As the organics break down their water holding capacity will change, for example bark will initially hold a moderate amount of water. After 6 months of decomposing, the water held will increase. As the decomposition continues, suddenly the bark will hold less water.

As organics break down, they will fall apart into smaller and smaller particles. These smaller particles will settle into lower levels in the pot, sometimes clogging up air voids between particles making oxygen poor pockets, here roots in those pockets will die, and begin to rot, becoming an avenue for pathogenic microbes to get into the vascular system of the tree, causing one catastrophic rot or another.

So while organics in the mix will allow a long weekend, it requires much more careful watering to prevent the issues of overwatering. Also, the media will be dynamically evolving, so watering frequency will change not only with the weather but depending on the age of the mix.

A pure pumice, lava & akadama mix. Or a mix that is 100% inorganic, will not change much over time. So the only variable in watering is current weather conditions and size of tree to size of pot.

One option, is to over-pot to some degree, and continue to use an all inorganic, lava-pumice-akadama mix. A sufficiently large pot will allow a long weekend. The hazards of over-potting in a all mineral mix are not as severe as over-potting in an organic mix.

Better solution is to look into automatic watering systems. If you enjoy tinkering with gadgets, this is the ideal solution. more reliable than the neighbor kid or a relative. With some work, can be close to 100% fail safe.

Great recap, think you for the detail.

I've been trying to think through how to pull off vacation this summer. I may look into some automatic watering systems just concerned about cost.