When to use soil with fine grit?

[QuantumSparky]

After all the resources I've read, including a very detailed study on substrate particle size, I have to ask...in what situation would you ever use fine grit in a substrate?

Perhaps @Pitoon could chime in as his JBP's seem to come planted in a gritty soil mix. Is it for small seedlings mainly?

From what I know, the goal is to have particle sizes match up with each other throughout each soil component. So having grit in the soil would, according to the article, have detrimental effects on the tree UNLESS the "same size particles" rule is only in reference to somewhat-established root systems and not root systems that are in a vigorous growing phase while the tree is still young.

Can somebody shed some light on when/why to use fine grit in a soil composition? I will be repotting most of my trees before next growing season and I want to make sure they have the best soil for their needs. Currently I plan on having them in standard organic mix from BonsaiJack

 

[HorseloverFat]

I believe the soil that Pitoon uses, that you are speaking of, appears to be sand, verm, aaand peat? He’ll be able to shed more light on it..

I personally use small, sifted, rinsed mussel-shell/sand as a component in SOME soils.. mostly for cuttings and seed prop. (Also da/perlite ‘fines’ occasionally) But not too often..

 

[Pitoon]

After all the resources I've read, including a very detailed study on substrate particle size, I have to ask...in what situation would you ever use fine grit in a substrate?

Perhaps @Pitoon could chime in as his JBP's seem to come planted in a gritty soil mix. Is it for small seedlings mainly?

From what I know, the goal is to have particle sizes match up with each other throughout each soil component. So having grit in the soil would, according to the article, have detrimental effects on the tree UNLESS the "same size particles" rule is only in reference to somewhat-established root systems and not root systems that are in a vigorous growing phase while the tree is still young.

Can somebody shed some light on when/why to use fine grit in a soil composition? I will be repotting most of my trees before next growing season and I want to make sure they have the best soil for their needs. Currently I plan on having them in standard organic mix from BonsaiJack

I primarily use peat/vermiculite/sand mix in a ration of 2/1/1 mixed thoroughly for my seedlings/rooted cuttings when I transplant. Getting them to root or germinate I usually use a different approach depending on the species. Grit helps to loosen the soil and allows drainage. You can somewhat control how you want the roots to grow out using different substrates. Coarse substrate will allow for thicker roots, while finer substrates will produce fine feeder roots. Remember you always have to keep in mind drainage, grit will assist. Roots that stay wet for long periods of time WILL rot. Of course there's exceptions like weeping willows and bald cypress that are water lovers.

Sometimes people want to complicate things. Take what you read with a grain of salt, most people that write articles can't back up what they write.

These air layers were left to grow out in very coarse substrate to generate thick roots, I could then spread them easier without damaging them to get a nice spread for the nebari. Some of them were ready to transition over to a finer mix to get the feeder roots going. Feeder roots will help to thicken the thick roots.



Here's what they look like after just a couple of months in the finer substrate, full of feeder roots. You'll note there's no large roots growing, just feeder roots here. After this step you just keep watching them and trim/prune as needed.

 

[ShadyStump]

Here's @markyscott's discussion on soil particle physics.

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

Just the science, devoid of anecdotal tripe. Made a world of difference for me once I got into it.

As Pitoon noted, the size of soil grain can make an enormous difference in the character of the roots.
Read markyscott's resource, and you learn that smaller grains can hold more water while still draining well. The trade off there would be oxygen flow to the roots.

I'm still working on just how to put all this info into practice for myself and my style of doing things, so, like the man said, grain of salt.

 

[QuantumSparky]

I primarily use peat/vermiculite/sand mix in a ration of 2/1/1 mixed thoroughly for my seedlings/rooted cuttings when I transplant.

Perhaps a dumb question but what type of sand do you use? I can't seem to find any suitable sand at my local hardware stores. I did find "builders sand" which I tried to mix for my propagation box but the stuff seemed like it gums up when wet and became super hard. And no it wasn't actually cement mix

 

[Pitoon]

Perhaps a dumb question but what type of sand do you use? I can't seem to find any suitable sand at my local hardware stores. I did find "builders sand" which I tried to mix for my propagation box but the stuff seemed like it gums up when wet and became super hard. And no it wasn't actually cement mix

No question is a dumb question, my friend!

You might have picked up a bag of polymeric sand which is used for pavers. This sand has a special additive to bind together when it becomes wet to lock in the pavers.

The sand I use is plain old 'play sand' the bag will usually have a picture of a kids beach bucket and shovel. There is also builder/paver sand, but it's not as clean as play sand. The builder sand will usually have small rocks and pebbles of different size mixed in it. There is a pound difference between the two types of sand, 50lb for play sand and usually .5 cu ft for the builder sand. There is also price difference by a couple of bucks.

If you buy by the yard this is where you can really find savings.

 

[QuantumSparky]

No question is a dumb question, my friend!

You might have picked up a bag of polymeric sand which is used for pavers. This sand has a special additive to bind together when it becomes wet to lock in the pavers.

The sand I use is plain old 'play sand' the bag will usually have a picture of a kids beach bucket and shovel. There is also builder/paver sand, but it's not as clean as play sand. The builder sand will usually have small rocks and pebbles of different size mixed in it. There is a pound difference between the two types of sand, 50lb for play sand and usually .5 cu ft for the builder sand. There is also price difference by a couple of bucks.

If you buy by the yard this is where you can really find savings.

Ah gotcha, I think I had originally heard lots of advice about "stay away from play sand because it's too fine grain" but I didn't realize that while such advice is true for a single-component substrate (I was researching "potting" media for my propagation box) it doesn't matter nearly as much when the sand is being mixed into a bunch of other components.

Pure play sand for a potting media = bad because drainage issues.
Mixing play sand with other components to make a soil mix = good

Thanks for the advice! They definitely have a bunch of play sand on sale so I'll probably pick some up

 

[Leo in N E Illinois]

Sand is a mixture of many different parent rock types, in most places, and can be a real crap shoot as far as purity is concerned. But there is such a thing as "good enough".

The cleanest pure sand, that is near 100% silicon dioxide, is sand intended for sand blasting. I used to get Wedron Silica 20/30 grade from where I worked. I'm retired now, can't get it easily anymore.

If you have a construction materials or industrial supply shop near you you may be able to source exotic sand blasting aggregates. Like a sand that is pure garnet, or other exotic materials. Bonsai is an art project after all. Garnets in your potting mix? Why not?

Potting media particle size. I advocate having as little range of particle size as possible. I DO NOT use sand in my potting media. If anything goes through a piece a window screen I deem it too fine for use as a potting media. For medium and small pots particles from 1/8th inch to 3/8ths inch is about right. Nothing bigger, and key is nothing smaller. This will maximize air penetration and water holding capacity of the mix. DO NOT ADD FINES. Throw away fines.

Read Marky Scott's Soil Physics article.

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

Slight modification of my prohibition. I will make up about 3 gallons of potting mix. It is made up dry. I then sieve it over 1/8th inch screen, a home made sieve using window screen will work close enough. Then I will moisten the mix. Some will rinse it to remove more dust. Then after the clean sieved media is damp, I will add a handful, about 6 fl oz, ( 70 to 90 milliliters) volume of fine sand. Mix to evenly distribute. This is a very small volume of fine particles per 3 gallons of media (12 liters volume of media). When I repot, I find the sand particles stuck to root hairs in a healthy looking way. Key is to eliminate fine particles that can clog up air penetration. Then add back just a small amount of a uniform particle size sand, to give hair roots a little "something" to grab onto.

The single best horticultural tool for a bonsai grower to have is a set of soil sieves. Anything that goes through the finest sieve in general should be discarded.

 

[Pitoon]

Ah gotcha, I think I had originally heard lots of advice about "stay away from play sand because it's too fine grain" but I didn't realize that while such advice is true for a single-component substrate (I was researching "potting" media for my propagation box) it doesn't matter nearly as much when the sand is being mixed into a bunch of other components.

Pure play sand for a potting media = bad because drainage issues.
Mixing play sand with other components to make a soil mix = good

Thanks for the advice! They definitely have a bunch of play sand on sale so I'll probably pick some up

To ensure there's no confusion here, the mix that I make with peat/vermiculite/sand is not really used for bonsai here. I use this mix for propagating and growing seedlings for pre-bonsai. The only time I will use this mix is for mame as I have noticed that mame do better in this mix in the smaller pots.

 

[Pitoon]

Throw away fines.

Never throw away the fines, they are the best for rooting cuttings.

 

[Leo in N E Illinois]

Never throw away the fines, they are the best for rooting cuttings.

Let's agree to disagree. I find cuttings root well in the bonsai mix I describe above as long as humidity is high. A plastic bag over the pot of cuttings usually does the trick. Fines in general "gum up the works". A small controlled amount of fines, as in a few ounces by volume of sand of uniform particle size, as in the Wedron 30/20, in several gallons of mix is beneficial, but more than a small amount you really do begin to plug up the works. Organic fines are the worst, they make a muddy gunk that does not breath about the 2nd or 3rd year. So I definitely disagree.

 

[Leo in N E Illinois]

Also for cuttings in general, I use "Sphag 'n Bag", long fiber New Zealand Sphagnum Moss or Chilean Sphagnum moss, I use the long fiber moss, as is, long fibers. Strike the cuttings into a pot that is softly packed with the damp, long fiber moss. Water after striking the cuttings into the moss, then pot the pot into a zip lock plastic bag, seal and set in bright shade. My other cuttings method is my sieved, fines discarded bonsai soil, pop the pot and cuttings into a zip lock bag, seal the bag and set in bright shade.

Both methods work reasonably well.

 

[Leo in N E Illinois]

I usually do not use any hormones. Really pretty old school. I will water with seaweed extract, and or humic acid, fulvic acid mixture. But no commercial rooting hormones. The humic & fulvic acids do have some role in stimulating roots, but they are not commercial rooting hormones. Too much of rooting hormones will inhibit root formation. So I error on the side of using none.

 

[Pitoon]

Let's agree to disagree. I find cuttings root well in the bonsai mix I describe above as long as humidity is high. A plastic bag over the pot of cuttings usually does the trick. Fines in general "gum up the works". A small controlled amount of fines, as in a few ounces by volume of sand of uniform particle size, as in the Wedron 30/20, in several gallons of mix is beneficial, but more than a small amount you really do begin to plug up the works. Organic fines are the worst, they make a muddy gunk that does not breath about the 2nd or 3rd year. So I definitely disagree.

Maybe I should be a bit more specific when I reply. I like to use mainly monto clay, diatomaceous earth, and pumice fines to root cuttings, and they are almost always tented to keep the humidity up. I have rooted cuttings in peat/vermiculite/sand mix, but I do that when I want to root cuttings directly into their growing pot to eliminate transplanting/repotting.

And yes, organic fines is not worth messing with as they break down too fast.

 

[Leo in N E Illinois]

@Pitoon - question, because I really am not familiar with the product. What is monto clay?

I am familiar with Turface, which is a calcined illite clay. A fairly stable product, much like crushed brick. The illite is mined in Calhoun County Illinois and in Virginia. Its calcined (fired) to make a stable particle. I've used it off and on for many years. My biggest complaint is the readily available grade, Turface MVP is too fine a particle for most of my bonsai mixes. I have not found a reliable source of the larger particle sizes. I have instead resorted to having pumice shipped to me. Expensive, but a better particle size.

I'm familiar with Haydite which is an expanded shale. I've used it once or twice, but there are no local outlets near me, and it doesn't seem "special enough" to pay to have it shipped to me. Very similar to a coarse particle Turface, or other calcined clay particle used for hydroponic grow mixes.

But what is monto clay? and how does it compare with Turface or Haydite?

Ooops! I just answered most of my own question. Monto Clay is montmorillonite, a soft phyllosilicate clay. And illite is also considered a phyllosilicate clay. Looking at the formulas, the illite, ( Turface ), has some potassium and iron in its mostly magnesium aluminosilicate structure. Where Monto clay is mostly sodium & calcium in its magnesium aluminosilicate structure.

Both are calcined to make a hardened particle. I see Bonsai Jack's uses monto clay in their mixes.

Basically I don't think there would be much difference. I would imagine Monto clay is more yellow to white, where Turface has a light brown rusty color due to the iron in it. I don't expect much difference at all in how they work as a component of potting media.

If I missed anything please weigh in.

 

[Paradox]

I use small particle (2-3 mm) soil for very small trees (shohin or smaller) or cuttings.

I do not use dust. That gets thrown out

 

[penumbra]

My understanding is that Monto clay is acid . I rooted a few satsuki in it right out of the bag.

 

[Pitoon]

@Pitoon - question, because I really am not familiar with the product. What is monto clay?

I am familiar with Turface, which is a calcined illite clay. A fairly stable product, much like crushed brick. The illite is mined in Calhoun County Illinois and in Virginia. Its calcined (fired) to make a stable particle. I've used it off and on for many years. My biggest complaint is the readily available grade, Turface MVP is too fine a particle for most of my bonsai mixes. I have not found a reliable source of the larger particle sizes. I have instead resorted to having pumice shipped to me. Expensive, but a better particle size.

I'm familiar with Haydite which is an expanded shale. I've used it once or twice, but there are no local outlets near me, and it doesn't seem "special enough" to pay to have it shipped to me. Very similar to a coarse particle Turface, or other calcined clay particle used for hydroponic grow mixes.

But what is monto clay? and how does it compare with Turface or Haydite?

Ooops! I just answered most of my own question. Monto Clay is montmorillonite, a soft phyllosilicate clay. And illite is also considered a phyllosilicate clay. Looking at the formulas, the illite, ( Turface ), has some potassium and iron in its mostly magnesium aluminosilicate structure. Where Monto clay is mostly sodium & calcium in its magnesium aluminosilicate structure.

Both are calcined to make a hardened particle. I see Bonsai Jack's uses monto clay in their mixes.

Basically I don't think there would be much difference. I would imagine Monto clay is more yellow to white, where Turface has a light brown rusty color due to the iron in it. I don't expect much difference at all in how they work as a component of potting media.

If I missed anything please weigh in.

Good info as always! The monto clay I use is a dark brown when wet. It also makes a very nice top dressing for the trees. Very easy to distinguish from wet and dry as the colors changes quite a bit.