Heat bed meduim? Pumice or bark " sawdust"

Was curious if anyone could clarify.

@Ira I know Ryan uses and talks about pumice as the heat conductive material at the bottom of heat beds ( depth being the key variable).

But when Ryan and Randy discuss about post collection Yamadori recovery Randy explains that for a single year and for trees that require rapid root growth, he has seen bark " sawdust" give superior results.

Why would you not utilize this at the bottom of a heat/recovery bed? Is the nuance dependant on the trees roots being directly in the meduim ( sawdust/pumice) vs in a pot in the meduim?

Warning: If anyone has not listen to this, please do NOT mistake this for regular sawdust! My intentions were not to confuse.

That would be my guess. the irregular shape and size of wood makes for good contact with structures like roots, but less contact for a ceramic pot. Pumice being smaller and more uniform would make better contact with pot walls.

Heat beds are also kept warm and wet so wood will break down pretty quickly and pumice wont.

Still, its an interesting idea. It seems like using coarse sawdust would work at least close to as well as pumice.

Thanks for sharing your perspective, much appreciated!

I went the route of saw dust in a raised recovery heat bed because of the cost deferential. I will share the results when winter in the Northeast has passed.

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Cool setup. What are you using for heat?

I have an iPower (Amazon link below) heat mat. Double insulated under and waterproof liner ( construction plastic) over that mat

amazon.com

Amazon.com : iPower GLHTMTM-A 20" x 20" Waterproof Durable Seedling Heat Mat…

Thanks. I’ll check it out.

Nice. Good luck and let us see how it goes!