Water retained by various soil ingredients

Peter Taggart petersirises@gmail.com
Wed, 24 Oct 2012 13:52:41 PDT
On Wed, Oct 24, 2012 at 9:50 PM, Hannon <othonna@gmail.com> wrote:

> The pumice available here, mined in eastern CA and in NV, provides good
> surfaces for roots and water to adhere to but water and roots do not pass
> through the particles-- the "holes" in the pumice are locked inside the
> individual pieces. This material has been a staple for cactus industry for
> years, but it should be noted that most wholesale production of cacti &
> succulent utilizes only a mix of organics like SuperSoil and fine perlite.
> There is often a sharp difference between successful approaches to nursery
> production versus methods of maintaining plants longer term by hobbyists.
> Since it is a natural product, what is sold as the same item (pumice) can
> vary from very clean and sharp-edged particles to soft-edged rounded
> particles with more dust-like fines included. I agree with Jane that the
> fines are helpful to the roots, in part by coating them and protecting them
> with a 'powder coating', especially when plants are dormant. Fines in
> general, especially organic ones, help with cation exchange (places where
> nutrients can be stored in the soil). It is unfortunate that pumice is so
> difficult or expensive for growers to obtain in practical units regardless
> of where they live.
> Scoria sounds like what is also known as cinder. This is volcanic material
> that is crushed in huge quantities to make cinder blocks and this seems to
> be its nearly exclusive use. A fine grade of cinder (black or red) with
> pieces 1-2mm is very clean and sharp and one of the best materials I have
> found to start seedlings of cacti, bulbs, etc. Again, with horticultural
> demand so low it is no wonder it is difficult to find a source for it.
> Dylan Hannon
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