Max root growth.. pumice or perilolite

Let me start by recognizing the different “stages” these two trees in are apparently very different… but are they? When comparing new air layerings to collected yamadori… the common state of the tree is help me get my roots under me ASAP…

Cutchins who propagates for a living is all in on perilolite. Paraphrasing but something like:When I need to drive root growth it’s always perilolite.

When it comes to yamadori which is where Randy makes his living he is exclusively utilizing pumice, with the exception of trees healed into bark dust.
I could possibly see that the size of the material Randy’s trying to drive roots in is much larger and perilolite is light and less stable, everytime it moves root growth is set back for a net negative? In theory what meduim drives the most rapid root growth and what are the variables/reasons ( trade-offs) for making this decision… I’m either missing something or don’t understand the why and I don’t want to be trying to get better practicing dogmatic reasoning?

Anyone have a guess or know?

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I am guessing that the major reason for the difference is availability. Pumice is readily available in Oregon since it is mined in the NW United States. Perlite is much lighter and therefore much cheaper to ship to Florida from where ever it is made than pumice.

In my experience perlite tends to drain a bit faster than pumice which may be an advantage in a hotter, more humid climate like Florida. It is also used extensively to root cuttings which I beelive is one of the core areas of David’s nursery.

Finally, I think the weight of pumice is useful for larger trees like yamadori as you stated.


@MartyWeiser Thanks this is the line of thought I was thinking and hoping. Since I am in the Northeast pumice is financially unrealistic if I can secure the larger trees and keep an eye on watering I can go with perilolite?

You should be good with Perlite. I had another thought based upon naked eye observation - the surface of perlite is smoother than pumice which would lead to less surface area to to hold water once the primary water had drained off.

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Another approach is expanded clay from the construction sector and then add bark for the final mix.

Perlite and organic is the standard horticultural mix for root growth. The majority of horticultural propagation is done with this. Normally this comes down to availability. I know a few people in the UK who are using this sort of mixture for collected yamadori with added molar clay too. Mind you, this is also their standard potting mix.

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@antelion I have no experience working with this combo of medium’s, but on the surface would this not stay too wet?

i guess it depends on the amount of bark added. The expanded clay actually dries out pretty quickly. That is why i do not like this combo (together with lava and pumice) as standard bonsai medium as it is used in some places.You are pretty much tied to a watering schedule regardless of the actual weather imo.