Kanuma soil and PH?

Ok, I know Kanuma is best used for Azaleas and comes from a different Volcanic region in Japan, and it is in fact acidic in nature ie; around a Ph of 6.3. At least that is what I got when I tested it. In fact it dropped my water Ph from over 8, if my PH meeter is anywhere close to being accurate. My question though is in two parts, 1) is the structure of Kanuma basically the same as Akadama with the only difference being it being more acidic? 2) Since my water has a high Ph could one use Kanuma soil mixed in with Boones mx to add acidity to the soil to counter the alkaline PH of my water? Or if one was only using Akadama, mix in Kanuma?

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Kanuma is softer than akadama and breaks down faster.

I think Ryan has said in the past it’s not an a great long term solution to fixing ph problems. If your water is consistently over 8 it might be good to figure out a siphon system to help bring your ph down.

Kanuma breakdown issues aside, adding kanuma to Boone’s mix will help add acidity to your soil. I saw a huge turnaround in my slash pines after adding in kanuma using the same old alkaline water I’ve got on hand. Prior to that I tried everything you’ve probably tried already such as chelated iron supplements and ph down in the water. I’ll let you know if I end repotting more frequently as a result of the kanuma crumbling.

@anderson.ppc Can you not collect rainwater? This is the easiest solution. You can get the large blue containers on the internet and buy taps for them. My water is 8 - 8.5 pH so I try to collect as much as possible. Though to be honest, I had that much water in my garden last night I had the fire brigade pumping it out to save the house…

Don’t know if you have already seen this video, Understanding Soil, but Ryan went through a lot on what he’s trying. I know I asked about kanuma during the stream and the major concern was the fact that the kanuma is so soft.


What about using distilled vinegar to bring your pH down. I did this during the summer when I burned through my rain barrel. It took a surprising small amount of vinegar to get the pH where I wanted it.

Minor point of clarification…Kanuma does not come from a different region of Japan, but a different zone in the soil profile. Both products occur in the type area for the formation in the filled valleys around the City of Kanuma. The Kanuma forms right below the organic rich humid layer at the surface of the soil profile and represents the most leached and residual portion, and the Akadama lies below the Kanuma. They both are developed from pyroclastic materials of the Kanuma Pumice deposits that washed into river valleys and then subjected to intense weathering that resulted in the agricultural lands and soils harvested for bonsai.

Don: That is really a good point and interesting. Since you seem to be in the know:):slight_smile: My curiosity about the two types of soil is piqued. So, given what you have said I am curious about how the difference in the two types of soils accounts for the way they are used ie: Kanuma used specifically for Azakeas. Both look and feel the same and from what I understand and have observed both have a very similar PH, ie: around 6.9. In addition, if one has the same size Kanuma, can it be used in place of or supplement akadama if you run out of akadama?

Thanks for your feedback and insight.

I think my last question was already answered ie: It has to do with the softness and how fast it breaks down. Correct

Anderson - For a deeper dive on the use of Akadama (and some info on Kanuma) see this post where I link to a site that documents the origins and possible alternatives to Akadama.Akadama Curious

The two clays are quite similar, but with far more leaching of iron from the Kanuma. I suspect Kanuma represents the idea soil for some azalea, but there are as many ways to blend soils together as there are bonsai practitioners. I would say that if you had to substitute some Kanuma for Akadama or vice versa, you will not see too much difference. Kanuma being lighter in iron, you might want to supplement that at fertilization time?

Any others have better advice out there for Anderson? Please weigh in…with respect to making soils work for different species, I am an unranked amateur. At our bonsai club, the experienced fellows and gals can make anything grow well in all manner of soils from straight pumice to pure Akadama to just “pine bark” which around here really means fir bark. The primary thing is to match the drainage and nutritional needs of the tree, and there seems to be multiple ways to make that happen.

I will be potting up with some Oregon clay-rich soils later this winter/early spring…so stay tuned for that. Just ordered 24 pond baskets and have 10 gallons of the Oregon clay to mix with the pumice/lava that I have pre-sorted and ready to incorporate.

But first, the crazy late winter snow/freezing event to get through!

Awesome, thanks so much for the information. Much appreciated!

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