It’s repotting time!

And that means we talk about soil mixes ad nauseum…

I get so many questions about mixes—and what I use—that I figured a post might forestall some of them. My current mix is based on what Mr. Suzuki used, which was a mix weighted to akadama, with the rest being pumice. I’ll first give what we did in Japan, and then offer what I do here.

Mr. Suzuki’s mix:

7 parts Akadama (approx. 1/4″ size and smaller)

3 parts Pumice (same size: 1/4″ and smaller)

For trees that had a bit of root rot, some charcoal was added in the drainage layer.

Now a few refinements. For conifers, we’d sift out the 1/16″ size; for deciduous, we’d leave that smallest particle size in. For both mixes the ‘fines,’ the dust, etc. was sifted out. Results in a bit of sifting, doesn’t it? And no small amount of coughing either. I remember aching arms, too. Suzuki had hundreds of trees.

I have altered these proportions to fit our situation: economics (akadama is expensive here, vs. only $3.00 a bag in Japan). 

My mixes:


1 part Akadama

1 part Pumice


1 part Akadama

2 parts Pumice

Lava is a good substitute for pumice, but I prefer pumice for its internal properties (much more gas exchange) and because it is lighter. A big box or pot of lava is a heavy thing.

The solid particles like decomposed granite, sand, rock, etc. are not as good as lava or pumice as they have no internal structure that can hold air. 

If desired, a layer of fine (1/8″) akadama/lava may be added to the top 1/2″  for better water retention in that hot upper layer and for looks. The only disadvantage of pumice is that it is white…

These mixes, with akadama as a water-holding particle, works for many different climate zones. I lived in Arizona for five years and used soil mixes with the same akadama content with great results. Now in the Pacific Northwest these same mixes show the same consistency: Strong growth, best ramification of fine feeder roots, and little chance of root-rot. 

I love this time of year…



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  1. Patrick Walz says:

    Hi Michael,

    I recently have gotten a couple year old chojubai red clones and started following your blog. I was curious as to what soil you use on your young chojubai when they are pre bonsai. I know you mentioned a couple times 50/50 akadama/pumice, but is that also your mix of choice for those you are just looking to bulk up, and if so what size (shohin, small, medium, etc) grit would you recommend for these babies?

    • crataegus says:

      I use pumice and bark/steer manure mix. 80% pumice, 20% bark/steer. This works for some years and gives a nice slow fertilizer release. I still fertilize, but having some in the pot seems to grow a stronger plant. After growing the young plant and developing structure, then I usually put in a 50/50 mix of pumice/akadama. 70% akadama is better if it’s not too expensive for you.

  2. Darren says:

    If you were to use decomposed granite, would sift out the fines/dust? I ask because a lot of dg is very fine particles and I’ve never seen them in 3/16+ particle sizes.

  1. […] for years – roughly one part each akadama, pumice, and lava. Michael Hagedorn recommends a similar mix of akadama and pumice. He also discusses the differences between lava and pumice in the […]

  2. […] from the advice of both American and Japanese bonsai professionals (more at Bonsai Boon and Crataegus Bonsai). Still, I find room for […]

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