In article , Henry writes

My understanding is that Perlite does not hold nutrients/water well and so
it's main role is to aid aeration and drainage, whilst Vermiculite holds
some water/nutrient and so also helps keep the compost moist and buffer
nutrient levels.




Vermiculite is 'organic'

Http://www.vermiculite.net/

but then Perlite seems to be as well

http://www.vermiculite.net/


I prefer vermiculite as it doesn't leave quite so many gaps in the
medium as Perlite. Perlite doesn't half blow around rather like that
expanded polystyrene packing stuff. Or worse still the insides of the
dogs' bean bags !!
--
Janet Tweedy
Dalmatian Telegraph
http://www.lancedal.demon.co.uk