Now there’s some pretty soil. 
With all the partisan political divisiveness of late, I figured that I’d introduce a calm, nuanced, and non-controversial subject into the æther. Try to, you know, relax the dialogues on the interwebs and facebooks a little, so to say. This is a safe subject. Indeed. It’s time to make the soil!
In that spirit, let’s talk about soil a little…..no one argues about soil, right? Before I begin, here are three links on soil from Da’ Blog: The epic one, The personal one, The update. Read them. There’ll be a test.
Let’s see now, we have lava (the pointy heads call it scoria. What do scientists know, right?) 
Lava is my go to, I’ve used nothing but it at times. It’s great for Florida, it doesn’t fall apart, has good shape and porosity, doesn’t hold too much water. Unfortunately, it doesn’t hold much nutrients either (this is called “cation exchange capacity” abbreviated henceforth as CEC. It is a measurement of the electrostatic charge of a particle in reference to fertilizer molecules. How much fertilizer sticks to a soil component. This is important in the coarse, granular soils we use because, startlingly, 75-80% of all fertilizer drains right out of the bottom of our pots. It helps for the soil particles to be able to hold a little between applications. At least I think so, there’s enough fertilizer pollution in Florida’s groundwater as it is now without me contributing to it too much more).
This next is expanded slate, a newer product that’s almost a ceramic, marketed by the Espoma company (and American Bonsai Tools too, I might add). It holds only about 10-15% of its weight in water and about zero CEC. I use it to improve drainage; in Florida we have rain, it being the Sunshine State and all. We can have more rain in a few hours than most places have in a month. This aggregate is basically to help keep my mix drier. 
Funny story, we once had a British gentleman (aren’t all British men, gentleman? Well, not really, I know one guy….likes to call other bonsai people names, not very “propah” at all, come to think of it….) visit the Orlando club and claimed that England had a lot of rain. Granted, it rains a lot in the United Kingdom of Great Britain, but it’s more like drool as opposed to the explosive projectile deluges we get here. Anyway, the funny thing is he kept asking if we had hawthorn yamadori and if we knew of a bloke called Tony Tickle. I said, “Mr. Tickle? Isn’t that a character in a children’s book? ” Hi Tony! Owe you a pint for that one.
Moving along, I have a pumice source now (the aforementioned American Bonsai Tools). I still don’t like the look of it but I’m liking most of the properties. Well, except for one: see, it doesn’t have a high CEC (because of the silica composition) but does, the way the pores work, (called index solution trapping) hold nitrogen in the surface matrix. What I’m learning and not liking is, when it’s relatively dry, it holds those nutrients and is very stingy in sharing with the plant, but in times of saturation, it will leach them excessively (as opposed to the way cation exchange happens). Here’s the scenario: in the summer, we have the flooding rains and then the heat dries the soil out pretty quickly. I’ll need to water again the next day if it doesn’t rain, ( I call this the “Wet/Heat/Dry Cycle”, it’s one reason why akadama doesn’t hold up well here). But, in the winter, the soil will stay wet for days, and pumice will give off too much fertilizer during these periods of saturation. Not good for trees that we don’t want to be actively fertilized at that time. I should add, this is mainly an American pumice problem (or what could be called a new pumice problem). The older the pumice or the more degraded it is, the higher the CEC will be. 
But that’s some high level stuff right there (go Here to read an abstract of a study done in Oregon on pumice, there are definitely some 25¢ words to learn) conversely, my favorite characteristic of pumice is it’s crushability by the roots. The roots need something to hold onto, to embrace and, much like the way your Aunt Joanne does when greeting you at the family Christmas get together, crush. Pumice should be soft enough for this (there are several grades of pumice. Everything from those stones you grind the callouses off your heels you get from wearing what my uncle used to call “come-hump-me-pumps, to horticultural grade. Which is really the cheapest grade. It’s soft, often floats, and works great in bonsai soil).
Since the pumice isn’t good at holding nutrients, my soil additive for that is pine bark, sifted, partially composted and ph controlled. I use Fafard organic soil conditioner. 
It holds water and fertilizer very well and the roots love it. And it’s a perfect medium for growing the microbes we need in a bonsai pot. I’ve written about mycorrhizal and bacterial symbiosis before, and every time I research it, there’s new information expanding our knowledge. The fauna down below is good for the flora up above.
I also use a calcined clay aggregate (OH NOOOOO!! The dreaded Turface!). It too has a relatively good CEC and holds water. It works good in Florida, much the way akadama performs but without the rapid breakdown that turns akadama into a brick. 
I don’t understand the vehemence that is shown towards this product. It’s not bad as a component in a soil mix. It could be this for one statement I overheard someone say “I’ve never deigned to even think of using a cheap product like that on my trees” that is the real antipathy. Take that as you will. In some parts of the country, turface is more expensive than akadama.
I will usually use an expanded shale product, but I’m out of it at the moment.
In case you haven’t figured it out yet (from this post and those linked above), I’ve done a lot of research and put a lot of thought into my soil. I don’t take someone’s word or use “traditional” soils just because they’ve been used for generations (For hundreds of years it was believed that bathing washed off the natural defenses that a body produced against disease. Before we discovered the germ theory of disease. And that bloodletting worked too, before we stopped believing in the “humours”. No one asked why though, did they?)
So here is this springs soil mix recipe. Notice that when I do my measurements, they’re a little heavy on some ingredients and lighter on others. Here you go:
One part lava (usually its two but I’m using pumice this time, an almost identical component)
One part pumice (and if you’re not pronouncing it “pooomice” you’re just not cool) 
One part expanded slate (ignore the leaves and twigs, they don’t count) 
One part bark (a little lighter on it). 
One part calcined clay (and its “calcined” not “calcinated”) 
This batch should get me through the next few weeks of repotting. Hopefully. A full batch fills an 18 gallon plastic bin. 
Like I said, isn’t that pretty? I should be a hand model.
Next few posts, I’ll be immersing myself in the wonderful world of the sugarberry tree.
Sweet.
Adam's Art and Bonsai Blog 
You’re working late, Adam!
>
LikeLike
Or early
LikeLike
Adam; I thoroughly enjoy your “tutorials” and try to abide as best I can – your are very enjoyable AND educational ! After perusing your latest – – I thought I distinctly recall you saying that soil composition should made of constant sizes of components. Your final mix appears to have larger sizes of the more absorbent materials. Is this to help retain water ?? I live in the Atlanta area, so moisture can be an occasional problem; either to much or not enough. Thank you for your time, talent and courtesies. Paul Larson
LikeLike
I may have said something like that, or similar, but you should have particles no smaller than 1/8″ or larger than about 1/4″ (I cheat on the larger a bit). What you shouldn’t do is stratify the soil, it should be mixed evenly throughout, not as some people teach by putting larger on bottom, medium in the middle, and smaller on top. That stratifying actually keeps a soil too wet
LikeLike
I’ve been using Turface for over 40 years, Never a problem! Except a lot of mineral deposits leach out of it!
LikeLike
In Chicago it’s not uncommon to use only Turface as your soil. Well almost, a layer of one stone depth of lava at the bottom, then Turface on top of that. One of these days I’ll try your more x and see how it does in Zone 7
LikeLike
Scratch that, Zone 5.
LikeLike
Botanic Garden recently moved away from pure Turface and finding better root growth. Wonderful article and breakdown. Thank you for the pumice article link.
LikeLike
…So Hector I am curious. If the Botanic Garden moved away from pure Turface what did they move to? Can you share any more information?
LikeLike
But I’m a student of Ivan Waters (former curator of the Gardens bonsai). So Turface and oak leaf mold it is.
LikeLike
…And, this was a fabulous, entertaining, insightful review of soil components. Very well written with just enough grins to make points clear. Fafard and a Turface mix have sustained my trees. This interested me enough to try some additional components. Excellent that AmericanBonsai carries other materials I’ll need for some good experimenting.
LikeLike
Hi Adam! My name is David and I discovered you via YouTube and enjoy your videos. I have a Serissa foetida (double snow rose) and a Texas Ebony. It’s my first foray into bonsai so it took me a little while to realize the 2 bonsai I’ve purchased are actually just seedlings. *facepalm* so I have my two bonsai seedlings in pots that are 1/3 gravel and filled the rest of the way with miraclegro: moisture control gardening soil. So far they are thriving, the Serissa is blooming and the Texas grows new leaves. About how long can I leave them in gardening soil before I HAVE to change their setup?
LikeLike
You keep it in growing soil until you reach the desired trunk thickness. Then you begging the bonsai process. On the Texas ebony it could be ten/twenty years as they grow slow in pots.
It’s only when they go into shallow pots when you use bonsai soil, otherwise the pot doesn’t drain well.
LikeLike
Thank you!
LikeLike
As I write this, it is the second day in February! Are you really gonna start re-potting some trees now? If so, what species can be done now and which ones should we wait on? I too live in central Florida and have not seen any temps below 40!
LikeLike
Temps aren’t so important to dormancy as lack of light is. Especially with deciduous trees. And we’ve already passed the equinox so the daylight is increasing.
For a tree to break dormancy it is triggered by temps, but the trees I grow don’t need too much dormancy anyway.
The juniper we grow certainly don’t, procumbens nana or parsonii or even the shimpaku. And the Japanese black pines are breaking dormancy now as well.
And because of the mild winter, many of my deciduous are starting to grow, if I don’t repot now I won’t be able to in a few weeks, they’ll be in full leaf.
Doing bonsai is very much a practice of horticultural techniques and you must observe the plant. Very little of what we do is set in stone because they are living things and we need to adjust according to what the plant is doing at that time. So dates or techniques may or may not be adhered to strictly in any given year. Think of them as guidelines and less of them as carved-in-stone rules.
LikeLike
I wanted to post a follow-up question about the fafard soil conditioner. For a while now I’ve been able to obtain a decent fine pine bark mulch product locally (NY state) that I sifted to use in my mix. But that product is no longer available so I’m searching for a replacement. Have never found fafard products in my area. In a previous message you made a comment about them changing the packaging. My reading suggests that fafard was bought by another company, sungro…and I’ve searched their website but can’t find anything like “organic soil conditioner”.
So I guess the question is, has the packaging changed, have you had any indication that it might not be available for long, anything like that? I like the idea of the stuff being partly composted but haven’t been able to find an equivalent product locally. Thanks!
LikeLike
It has changed. Try the BWI companies site, here’s a link to the product : http://www.bwicompanies.com/catalog.aspx?type=grower
LikeLike
Adam, you might want to look into buying up all of the soil conditioner you can find. I just spoke to the new company (sungro that purchased fafard) and they tell me that they’ve discontinued production of the organic soil conditioner. If that is true, you are probably buying leftover stock that will not be replenished. You might want to check with your supplier (bwi) to see if they can verify this.
Maybe someone else produces a similar product, but I haven’t found anything up here in NY.
LikeLike
Love the blog! I live in southern Arizona, and the posts are very timely, since I’m doing a lot of my potting right now.
Make sure to try your local landscaping shops. I live in the Yuma, AZ area, and a local nursery/landscaper sells 3/8″ lava rock for $2.25 / 5 gallon bucket. Once I’ve sifted it, I end up with about 3 gallons of usable potting material. They also have suitable gravel, grit and mulch. I have to sift it, but it’s worth it for that price. I end up using any leftovers in the yard.
LikeLike
Reblogged this on Wolf's Birding and Bonsai Blog.
LikeLike
I’ve been using a haydite (expanded shale) and pine bark mix and adding some Optisorb which seems to work fairly well in the New Orleans climate. My mix is fairly multicolored like yours. Do you use anything as a top dressing when you show your trees – or just your regular soil with moss?
LikeLike
I don’t worry about a top dressing when I moss the tree for a show, though on some trees I’ll too dress with sphagnum after a repot
LikeLike
Italian bonsai masters usually avoid using lava in bonsai soil and they recommend to not use it because roots could penetrate inside every single piece of lava. But, thanks to my little experiments with mix soils, i always thought it was very good for plants. Maybe because i live in Sicily (south Italy) and Sicily and Florida have similar weather. So thanks for havi confirmed my opinions and for your post, and your blog too. Greeting from palermo
LikeLike