perlite, pumice,

Joe Shaw
Tue, 04 Jul 2006 15:14:07 PDT
Hi Gang,

I can only second the frustration voiced by John Lonsdale.  I cannot find 
good perlite, and a search for pumice revealed no suppliers within 200 miles 
of Houston, TX area.  Neither the bonsai society nor the various cactus 
societies had good leads.

I've given up on finding good perlite (or pumice), and have started using 
substitutes; I don't know if they are the best, but they are the best in 
terms of availability and my willingness to spend money.  I use scoria (lava 
rock such as is used for landscaping) and Styrofoam peanuts.  Both have 
drawbacks and benefits for me.  Styrofoam peanuts are essentially free for 
me from my workplace.

Because it is so rainy here, I plant cacti, some bulbs, and many agaves, 
etc., directly in scoria.  I fill the container with scoria, or a mix of 
scoria and Styrofoam peanuts.

Then, I pour a soil mix over the chunks.  Sometimes, the soil mix is only 
10-15% organic matter, so the whole affair is really 100% scoria (by 
volume), with other materials filling some of the interstices.  Along with 
fungicides, extra water in dry periods, and other measures, this seems to 
satisfy many xeric plants.

The whole perlite size-reduction issue is perplexing.  I wonder if we plant 
growers who have noticed the difference just don't provide a large enough 
market for the vendors.  I've tried some other possible subsitutes such as 
Turface, and find that expanded clays hold too much water.  Drystall is one 
option (horse bedding material made from volcanic aggregates), but it is 
apparently not offered in this area.



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