clarification on soil particle size vs root size for pre bonsai in grow pots

[stroven]

After reading a lot of the information in the forum about particle sizes, it looks like the general takeaway for bonsai is:
-smaller particle = finer roots + more water retention
-larger particle = thicker roots + more aeration

Obviously there is a lot of nuance to this guidance given pot size/shape, tree size/shape, species climate and of course substrate.

I am trying to understand if/how this carries over to pre bonsai trees that are being developed in a big pot such as a plastic nursery pot (example)?

Nearly any nursery will sell trees in such pots, in regular potting mix (I think the main ingredient is Pete moss?), which is an extremely fine particle.

When I take a nursery tree out of its pot, a mix of tap roots and other thick structural roots exist, not just fine feeder roots even though the soil is very fine.

So do the principles around particle size relating to root size simply not apply to trees being developed in this way? Could there be other factors at play such as a more relaxed watering regime in the nursery, the excess space in the pot for roots, etc?

Reason I ask is I have 2 nursery trees (crepe myrtles) still in their original grow pots that need repotting. They are not ready for bonsai pots yet so I plan to up pot into a bigger grow pot. I own pumice, akadama, scoria, sphagnum moss, sand, and Ofcourse bags of regular potting mix. I’d rather not use up all of my expensive, hard-to-find Inorganic soils if I am just potting these up into a bigger nursery pot for another year. But I will if it is going to mean faster growth. Potting mix is simply cheaper and more readily available. I was planning on using this soil which claims to be for bonsai but is really just regular potting mix in a smaller, more expensive bag LOL.

Thanks!

 

[Mikecheck123]

Relaxed watering is one factor, but by far the biggest factor is cost. Bonsai soil is EXPENSIVE! It's expensive to acquire, sift, and mix all the ingredients both in terms of labor and time. Even more expensive to go and buy it.

So it's simply prohibitively expensive for regular landscaping trees at a nursery.

 

[stroven]

Relaxed watering is one factor, but by far the biggest factor is cost. Bonsai soil is EXPENSIVE! It's expensive to acquire, sift, and mix all the ingredients both in terms of labor and time. Even more expensive to go and buy it.

So it's simply prohibitively expensive for regular landscaping trees at a nursery.

So you're suggesting that it is in fact superior (by superior I pretty much mean faster growing speed), even for this type of developmental growth? If that is your opinion, would largest particle size possible be better?

 

[ajm55555]

Introductory Soil Physics - Updates

www.bonsainut.com

 

[Potawatomi13]

Personally have done fine with ALL personal trees with bagged Wee Tree nursery Bonsai soil mix. Used straight from bag no sifting. Did not have any krapadama in it, was composed bark, smaller amounts of sifted lava & pumice in 1 cubic foot bag. About $18 6 years past. Doubtlessly more now however pretty good mix for most things both conifer, broadleafs. Whether ground, nursery pot, clay pot, grow box need to periodically manage root growth/repot, be careful to have EXCELLENT drainage, make extra holes, watch watering. This mix largely falls off roots when removed from pot. Particle size depends on size of tree. Only biggest trees over 2-2 1/2 feet need big 1/4-5/16 particle size.

 

[eugenev2]

After reading a lot of the information in the forum about particle sizes, it looks like the general takeaway for bonsai is:
-smaller particle = finer roots + more water retention
-larger particle = thicker roots + more aeration

Obviously there is a lot of nuance to this guidance given pot size/shape, tree size/shape, species climate and of course substrate.

I am trying to understand if/how this carries over to pre bonsai trees that are being developed in a big pot such as a plastic nursery pot (example)?

Nearly any nursery will sell trees in such pots, in regular potting mix (I think the main ingredient is Pete moss?), which is an extremely fine particle.

When I take a nursery tree out of its pot, a mix of tap roots and other thick structural roots exist, not just fine feeder roots even though the soil is very fine.

So do the principles around particle size relating to root size simply not apply to trees being developed in this way? Could there be other factors at play such as a more relaxed watering regime in the nursery, the excess space in the pot for roots, etc?

Reason I ask is I have 2 nursery trees (crepe myrtles) still in their original grow pots that need repotting. They are not ready for bonsai pots yet so I plan to up pot into a bigger grow pot. I own pumice, akadama, scoria, sphagnum moss, sand, and Ofcourse bags of regular potting mix. I’d rather not use up all of my expensive, hard-to-find Inorganic soils if I am just potting these up into a bigger nursery pot for another year. But I will if it is going to mean faster growth. Potting mix is simply cheaper and more readily available. I was planning on using this soil which claims to be for bonsai but is really just regular potting mix in a smaller, more expensive bag LOL.

Thanks!

A comment on your particle size summary mentioned there, particle size used is dictated by the size of the pot, ie a small shallow pot, would require a finer particles as it cannot physically hold a lot of water, but if you feel like watering 5 times a day, you can go with larger particles. The only reason bonsai enthusiast tend to use small particles in a small pot or large particles in a large pot, is basically a combination of water retention requirements as well as an attempt not to repot to often. But one correction i need to make is that larger particles lead to large roots, this is not correct, fine compacting substrate lead to larger roots, as the roots tend to go in search for oxygen and resources, but large roots is basically a function of time and resource availability, ie given long enough time all roots will grow larger eventually.

With pre bonsai, you want explosive growth, which things like potting soil can provide, but they tend to be horrible on the aeration side. Bonsail soil can also provide explosive growth, but it is intended to promote ramification and eventually slow down growth without affecting the health of the tree too much. It's also not uncommon to repot prebonsai every year, so this alone makes using specialty bonsai soil a big ask to use for prebonsai. But it's one of those questions you need to ask yourself, are you ok with putting your $1 tree in $15 soil only to report next year into $15 soil again? If so, then go ahead. Most people tend to keep it inexpensive until the tree gets into a refinement stage and the tree is worth more than the soil it is in.


But inexpensive doesn't need to be bad soil, you get great cheaper alternatives like perlite/leca that can be used in conjunction with potting soil to improve aeration and obtain explosive growth. But all this, depends on your ability and schedule to water the trees, as learning good watering practices is really more important than the soil ie learning how to water your soil with the best effect

 

[stroven]

A comment on your particle size summary mentioned there, particle size used is dictated by the size of the pot, ie a small shallow pot, would require a finer particles as it cannot physically hold a lot of water, but if you feel like watering 5 times a day, you can go with larger particles. The only reason bonsai enthusiast tend to use small particles in a small pot or large particles in a large pot, is basically a combination of water retention requirements as well as an attempt not to repot to often. But one correction i need to make is that larger particles lead to large roots, this is not correct, fine compacting substrate lead to larger roots, as the roots tend to go in search for oxygen and resources, but large roots is basically a function of time and resource availability, ie given long enough time all roots will grow larger eventually.

With pre bonsai, you want explosive growth, which things like potting soil can provide, but they tend to be horrible on the aeration side. Bonsail soil can also provide explosive growth, but it is intended to promote ramification and eventually slow down growth without affecting the health of the tree too much. It's also not uncommon to repot prebonsai every year, so this alone makes using specialty bonsai soil a big ask to use for prebonsai. But it's one of those questions you need to ask yourself, are you ok with putting your $1 tree in $15 soil only to report next year into $15 soil again? If so, then go ahead. Most people tend to keep it inexpensive until the tree gets into a refinement stage and the tree is worth more than the soil it is in.


But inexpensive doesn't need to be bad soil, you get great cheaper alternatives like perlite/leca that can be used in conjunction with potting soil to improve aeration and obtain explosive growth. But all this, depends on your ability and schedule to water the trees, as learning good watering practices is really more important than the soil ie learning how to water your soil with the best effect

Amazing breakdown of information, thank you! Very helpful.

Good call out on re-potting frequency as another variable, bonsai repotting frequency would be much lower.

And excellent point about comparing soil cost to the trees value while it is being developed. Most of my trees are $10-$20 from various nurseries and are easily replaceable in their current state.

Yes one thing I forgot to mention was mixing potting soils. Again with bonsai that are past the explosive growth phase and are in a bonsai pot, I read that particles should be uniform in size. However when we talk about developmental potting using fine soils, its very common to mix in a larger particle (whether it be perlite, bark, pumice, lava, etc) with the fine potting soil to enhance oxygen. Again, I observe that this is contrary to the guidelines for bonsai so interesting to note.