Growing medium

Thu, 12 Jul 2012 12:20:52 PDT
The silty sediment can be quite helpful in clinging to roots and protecting
them from drying in an otherwise open "clean" mix. A lot of these fines
wash through after the first few waterings.


On 12 July 2012 12:05, Gastil <> wrote:

> Having heard good things about pumice on this list,
> I went to our OSH and purchased a small bag of Black Gold brand pumice.
> It was about 10 times heavier than I expected pumice to be, but they
> assured me that was just because it was wet.
> At home, I noticed it had a lot of dust, which I did not think I wanted in
> my growing medium
> (not having read the note from Jane yet about the dust containing useful
> minerals).
> When I washed the pumice, I noticed it sank. I expected pumice to float.
> The pumice in Baja California floats and resembles styrofoam.
> I wrote to Black Gold and they replied
> "The Black Gold Pumice that you bought comes from a source in central
> Oregon,
> the same source we have used for a long time. Chances are that you will
> get the
> same type of pumice in California, Oregon and Washington, if you buy Black
> Gold.
> This is a denser pumice, but should not affect the porosity you are
> seeking.
> The dust comes from the pumice rubbing against itself in the packaging as
> it is moved around."
> I also noticed when I washed it that I could sieve out the sizes to get
> pebbles for topping and
> grit to sand size for growing medium and could wash away the silt-sized
> sediment.
> - Gastil
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