AusBonsai

So, I started out with a simple enough question - what is akadama.

The first site explained it was a volcanic clay, heated. A few more sites stated the same. All reputable sites, so I thought I had the answer.

Then I started reading that akadama is in fact just a form of pumice. With people actively correcting others who referred to it as clay or soil. Now, slightly confused.

I was like, okay, akadama is just another kind of pumice - and pumice is a type of volcanic rock.

Then I started reading the debates about how akadama is better than pumice, you should mix pumice and Akadama, and the two are completely different.

My question is this... does anyone out there actually know what akadama is.

50% say it’s just a form of pumice (if this is so, why do people pair the two off like they are polar opposites)
50% say it’s volcanic clay.

My only assumption is that it’s both... that is, it’s Pumice that has broken down into a sedimentary form of clay. Just an assumption.

But based on all the knowledge out there. No one knows.

End of rant.

I think some people out there are a little confused or have misread something.

Akadama is a volcanic clay that is heated. While that clay may have formed from pumice, it does not have the same properties as pumice stone. Clay is defined not by its chemical makeup, but by its individual particle size which is less than 0.002mm.

(This is coming from 3 years of studying soil science at University)

Side note - Kanuma on the other hand is a pumice stone.

Thanks for that.

Yeah, I managed to find an in-depth piece about it.

You are right, it is clay which has formed from the breaking down of pumice.

I guess that’s why people are confused.

Akadama is not just clay. It is COOKED clay.
When the wet clay in the ground gets heated to high temps by a nearby eruption the water expands into steam pockets and the clay gets 'fired' into a type of stone. How hot and how quick it got heated influences the quality of the akadama. Like all mined products there is great variation between different sources and even within any particular pit quality may be different.
Calcined clay like perlite is artificially made but is essentially the same thing but the chemical makeup of the base clays may be different from natural akadama. Perlite also tends to be a bit less dense than natural akadama.

My understanding is most Akadama is heated by man, not naturally?

That is, the clay is mined and then put through a furnace.

I just heard that akadama is rolled then heated and then crushed and screened. Not sure if that is the case but it is a subsoil/clay. The point of akadama is that it is broken up by root action and forms finer and finer particles as it ages thereby helping with finer root growth and ramification of the branches.

When the wet clay in the ground gets heated to high temps by a nearby eruption the water expands into steam pockets and the clay gets 'fired' into a type of stone. How hot and how quick it got heated influences the quality of the akadama.

The process of clay formation occurs as such: During an eruption the super-heated rock (lava) is ejected from the volcano and rapidly cools forming volcanic rocks (such as pumice or scoria). Over millenia these rocks are weathered by chemical interations (mainly water and oxygen), breaking down in size until they form clay (rock to sand to silt to clay). The quality of Akadama is down to the chemical composition of the volcanic rock and the process of weathering.

Calcined clay like perlite is artificially made but is essentially the same thing

Perlite is actually a glass product that is made by heating crushed mineral rock. The process is very similar to how pumice and scoria occur in nature.

My understanding is most Akadama is heated by man, not naturally?

You are correct. Akadama is only heated to low temperature (around 300C), mainly for transport and storage.

All I know from my own observation is that when I crushed wet akadama, it reminds me of the clay in rice puddies in southeast asia. My teacher told me it's a rich and fertile loam soil.

I am pretty sure, based on the material I have read now and informative posts on here, it is simply clay formed from the break down of volcanic pumice. Explains why people refer to it as a form of pumice. A form, due to it being derived from, but distinct in its own physical character i.e. a clay.

I am also certain there is a lot of motivation to keep akadama as this somewhat mythical material, which doesn’t hurt the exorbitant price tag.

I have personally not used it before, but have ordered a bag. Given the expense and the necessity to change every two years, due to the break down, it would want to be pretty good.

Have also ordered some pumice...

In relation to lava rock, I am think about buying the lava rock sold at Bunnings and just breaking it down into smaller pieces. You can get a large bag for 6 dollars.

Cutty wrote: ↑April 14th, 2020, 7:02 pm I have personally not used it before, but have ordered a bag. Given the expense and the necessity to change every two years, due to the break down, it would want to be pretty good.

I don’t use akadama, but I know it lasts more than 2 years, that’s part of its appeal.

Everything I have read says it should be changed after two years as the fired clay breaks down and prevents proper drainage. That is the reasons lots of people don’t use them for pines and trees which don’t like a complete substrate change.

Granted everything to do with Bonsai seems to be personal opinion and subjective. Probably why the information is so confusing and conflicting.

I have used Akadama with lava rock and pumice as is the current thought process and the virtues of expounded at length.

I can’t say I’m overly thrilled thus far. Perhaps the stuff I have used has been low quality, but it seems to break down incredibly quickly and then retain water like it’s going out of fashion. I’ve found it very hard to manage my watering through wet winters as it’s been difficult to dry it back enough.

I’m still searching for something more reliable and still reasonable convenient to source than the store purchased mix. Akadama, at least the stuff I have used, ain’t it.

Coming from a non bonsai background.

I still find it hard to fathom the lack of, and in most cases, absence of organic material.

Compost seems to be a dirty word in bonsai. I understand the issues around compaction and the Small pot size. I always cringe when I see people buying a high organic potting mix at Bunnings. You just know within 6 months it will be like concrete.

I note a lot of renowned bonsai places, like Herons, still incorporate a little bit of organic material. I am not sold on the 100% inorganic mix of akadama, pumice and lava rock.

I hear spaghnum moss works wonders for sick bonsai.

Thanks Evan for putting in your valuable info into this thread and Treeman for your insight on how the roots do break it down eventually.
There a several hardness grades of Akadama and I Import what is termed "Hard Akadama" as i find it a good fit for our climate and environment.

Regarding the longevity of Akadama, some people will repot every year, some every 2, and some will go even longer for Pines and Junipers.

I have clients that use Akadama as bottom substrate in Shrimp tanks. They are finding in that application it lasts for about 2 years before needing replacing!
Many of the Succulent and Cactus growers use Akadama and Kanuma as they find it performs very nicely over long terms

For myself most of my trees are repotted every year as that suits me and when i do repot, as i use a totally inorganic mix I wash out the muck and reuse most of it. If required I top up with fresh ingredients.

Ken

Cutty wrote: ↑April 14th, 2020, 10:18 pm Coming from a non bonsai background.

I still find it hard to fathom the lack of, and in most cases, absence of organic material.

Many people find it amazing that you do not need organics in your pot.

for me the notion that inorganics is required to provide nutrients falls down when you realise we flood our pots everyday with water and after a month, any nutrients in the soil will be leached out anyway.
I have been using 100% inorganics for 15+ years now and do not need fertilise any more than anyone else to maintain tree health so the substrate in the pot makes little difference.

Some Bonsai artists like to add some organics into the mix for deciduous trees, but I have never seen the need.

I hear spaghnum moss works wonders for sick bonsai.

Well that depends on what is wrong with them.

Kne