Oregon “Akadama” Candidate - 2nd Look

Went down a bit of a rabbit hole trying to do inexpensive microphotographs of the Oregon candidate for closeup inspection and comparing to imported Akadama. Long story short, my iPhone with a $5 hand lens taped to it is better than a $30 digital microscope or the $130 digital microscope I purchased on Amazon.

I am still getting set up for doing basic physical testing of the materials, delayed due to tangential impacts from wildfire season…and of course the store-bought microscope debacle…but here are some decent close ups of various materials including: Akadama, the Oregon candidate/replacement, Kanuma, and high-quality diatomaceous earth. All granules approximately 1/8-1/4 inch in size.

Clockwise from top left: Diatomaceous Earth from Daybreak Gardens, Akadama, Oregon “Akadama” Candidate, and Kanuma. Harbor Freight hand lens (with Scotch
double-sided tape) and the cheaper (and better) of the two digital microscopes ($30).

Close-up of DE. Grains are rounded on edges, but the clasts themselves are still a bit angular. There is no visible porosity, but the density is very low and knowing what it is can expect it to be very porous. I will do some water absorption tests on this and other materials later in winter.

This is the best close-up of the imported Akadama…showing much surface texture and the yellowish brown clays.

Slightly wider view of Akadama

Here is the Oregon Akadama Candidate showing fine root material, much deeper brown coloration and fresh broken texture. The material is screened once for size and arrived very damp. The color lightens only slightly upon drying.

Slightly wider view of same Oregon Akadama candidate material.

Finally, a close-up of the Kanuma grains showing very well rounded clasts and a surface coating of fine dusty clays.

And to close the door on why a $5 hand lens strapped to an iPhone beats a store-bought digital microscope…


Could the processing of the Akadama be contributing to the roundness of the particles?
BTW , really tremendous work!!!


Yes on processing rounding the grains. I did a quick crush test on the previous (1st look) and the true Akadama is definitely a bit more durable. I think if the Oregon material were processed (dried, grass and roots screened out) there would be a lot of waste dust.

I have 10 gallons of the new material and I am trying to figure out what to try it out on this potting season. Perhaps some volunteer maple starts…

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Ryan mentioned that there’s a source of clay in Oregon that is basically identical to akadama. Something about volcanic activity in the area being similar to that in Japan. The problem is that the cost of mining/processing it makes it difficult to make a profit.


The Oregon akadama doesn’t look as ‘clean’ as the japanese equivalent. Perhaps there is still a bit more organic within the structure. Maybe another few thousand years left in the ground to make it pure :wink:


I have heard that too. But no one seems to know (or willing to tell) exactly where. I am interested in it from the scientific perspective as well as the utility of having an Oregon source to replace the imported source. It would be simpler and cheaper to simply continue to buy Akadama imported from Japan…but it would be satisfying to break that dependency and the reduce the carbon footprint associated with shipping across the Pacific.

Working against two different disadvantages here…
First, the limited information about the Japan deposits that are quarried and processed. A bit of information about the processing and some good shots of the quarry, but the actual nature of the soil formation and its origins make finding an analogue here more difficult.

Second, on this side of the pond, there is limited documentation of clay bodies or deep soil profiles such as those evident in the pictures coming out of Japan. Our Cascade Mountains are more recently active than most of the volcanoes in Japan, and the older deposits are covered by more recent ones. Again, if the exact source/evolution of the Japanese deposits were known, it would greatly reduce the number of places to look.

It makes a great deal of difference if the volcanic deposits are from airfall tuff mantling widespread areas, or are debris flows deposited in drainage channels. In either case, the next factor is deep, intense weathering of the deposits to form leached clays.

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True that the Oregon stuff is full of organic material including both roots and grass blades. I suspect the material is from the deeply weathered basalt deposits similar to the Red Hills of Salem and is a surficial deposit. Akadama is harvested from quarries that are a few meters thick…and the weathering zones are what separate the overlying humic material (black soil) from the underlying Akadama and Kanuma zones.

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Another important question is how long the Japanese can sustain production. When I first started with bonsai hardly anybody used it (or had knowledge of it) and even professionals steered clear of it. When you consider how many of us there are around the world it is quite staggering how much must be being quarried. I also know that Japanese growers of ordinary plants use akadama also although that being of a lower grade. Perhaps a soil analyst could do an accurate comparison.

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I also wonder about some of the clays that are found in the southwest (New Mexico, Arizona, Colorado and Utah). There are a significant number of ancient volcanos of various types in these areas and Native Americans have mined and used these clays for pottery for centuries. The color of the raw clay is very similar to that of Akadama. The land is dry now but prehistoric evidence indicates that these areas were very wet in the past.

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Very cool stuff! Ive been using the hand lens taped to the phone technique and I agree, it is the best.

Maybe the next step is to pull out the Coddington lens or the Hastings Triplets instead of the dollar tool store lens!

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You mention doing water absorption tests. For those who are not aware, you can easily measure the field capacity FC and saturation porosity SP of any aggregate for comparison. These are, respectively, the water- and air-holding capacities. All you need is a smallish bonsai pot (~1 qt works well) with drainage holes, duct tape, and a digital kitchen scale. The process is described in an article from the Journal of the American Bonsai Society here and in “The Why, What, and How of Bonsai Soil”, an inexpensive paperback booklet in the bookstore of the American Bonsai Society, both authored by me, based on suggestions by others.

Briefly, you weigh the empty container [M1], the container filled with water to the brim, with duct tape over the drainage holes [M2] (those two give you the volume, V=M2-M1, because the density of water is 1 g/cc), the container filled with dry substrate [M3], the container filled with substrate and water [M4] (again, to the brim), and, finally, the container filled with wet substrate after you’ve pulled off the tape and let it drain [M5]. With these measurements, FC=(M5-M3)/V, and SP=(M4-M5)/V.

In my experience, good akadama has FC=~22% (water holding after drainage, or bit over a fifth of the volume), and SP=~36% (air holding after saturation and drainage, a bit over a third of the volume). The quoted numbers apply to 2-6 mm grain-size screening. This is all explained in more depth in the references with photos and more verbiage. It would be fascinating to see where the Oregon candidate sits with respect to those.

Samples of diatomaceous earth that I have measured hold way too little air and way too much water, but different sources may yield different results. I have seen significant variations in results among samples of the same aggregate based on source, so one has to be careful and quantitative about specifying what one uses. There are better and worse akadama, lava, pumice, etc. The air-holding capacity (SP) is typically the most difficult to achieve; that is where the better volcanic aggregates tend to shine.


This is great info. Thank you Brian. I did some quick and dirty experiments just like it (have to find my notes) but will get back to this type of basic data gathering by spring at the latest.

I will also be potting some trees in development to see how they fare. In terms of building a soil to pot, I am thinking about using it approximately 50% with additions of pumice 25% and scoria (lava) about 25%. I have a bunch of presorted/premixed lava/pumice so I can experiment with adding different amounts of the Oregon Candidate to that.