I have studied that page well and truly David. Will do some experiments to try what suits best for my bulbs in this climate. Also will be checking up with the suppliers of the pumice as to what I can expect of their "washed" pumice if bought in bulk. And try some containers with baked clay kitty litter. And find a quicker way to wash pumice myself. I should have known this 5 years ago. Would have saved me some problems. Ah well, at least I could ask, and read the Wiki. And now improve matters. Thank you one and all. Ina On 3/07/2013 11:03 p.m., David Pilling wrote: > Hi, > > More fine material will make the medium more water retentive - the laws > of Physics can't be avoided. > > How water retentive a medium is, can be measured by a simple experiment, > see the PBS wiki page: > > http://pacificbulbsociety.org/pbswiki/index.php/… > > Instead of words, which mean different things to people, it would be > possible to quote numbers for the ideal medium for species. > > > -- Ina Crossley Auckland New Zealand zone 10a