For those of you in States where pumice is difficult to find. I would suggest figuring out a way to have it shipped in Bulk or coming to visit CA and bring a big truck load full back. Here's a couple places you can purchase it for about $50-100 a truck load. Bag it up and sell it to your friends.
Here's where I get mine, you have to wash it because it's really dusty. San Luis Obispo, CA:
http://airvolblock.com/cm/General/Bulk_Products.html
CA Bay Area:
http://www.americansoil.com/sand_gravel.html
To help improve Bonsai in the US I believe we have to start thinking of multi generation Trees, which is part of the reason I believe using a volcanic soil is so important. Japan is so far ahead of us because they are working on material and knowledge which was built upon for generations now. While I hope I still have time to do Bonsai, I’d like to pass my trees onto future generations. Not sure if everyone caught the responses on Michaels blog, however I believe he addresses some of the responses on this thread, brings up some important points which are not considered in the US often enough and he is very good at communicating through writing.
Quotes from Michael:
"Yes, some organics like coir and bark can produce good roots, but seemingly only over the shorter term. We want roots that if need be can be left in contact with their soil particles sometimes for decades. In the interior of the soil mass in Japan sometimes things are not touched for a very long time, if things are happy there. And they only seem to remain happy if in a volcanic mix. The exterior is changed, the interior is only worked on periodically and never as severely as in the west because there is no need to.
There is a lot to learn, but we’ve been trying to reinvent the wheel over here in places where it’s not wise to do so. Much of horticultural soil science assumes replacement in several years time. In bonsai, this is simply not the case. Sometimes in the interior of the mass we want it to remain there for much longer. And that’s the whole problem with western assumptions of repotting: Changing out the soil mix. With organics you have to because they break down into something that gets worse and worse over time."
About Dry Stall
"Yes, Dry-stall is pumice. It is useful for bonsai soil, not bad, but the sizes are a bit small. So for smaller pots this product is ok. The other thing is that it seems crushed, and therefore it has less pore space than the pumice taken up buy shovelful in the Cascades which is rounder. But Dry-stall is usable."
"Hydration is a problem with Turface, Oil-Dri and Profile; they all have strange water holding properties and can become oddly water repellant on top on a hot, dry summer’s day, impeding water penetration. So it works both ways and is a very dangerous situation.
What I’ve seen between different soil particles is that Turface does not create a good root system, and pumice, lava, and perlite are far better for fine root growth and allow more uniform water penetration. We can argue about it all day and for what reasons, but the fact is it is not as good as other particles. Yes, you can find a way to use nearly anything. I’m just saying Turface has the narrowest parameters of healthy root growth of anything I’ve seen. Even under the best of husbandry trees grown in Turface have fewer fine roots than other soils. I don’t see a reason for using it when there are better options."
