Welcome aboard Hamish, Hi Everyone, I like your experiments Hamish, its a fun & interesting contribution, for myself, I live on top of part of the great dividing range in Australia west of Brisbane & North of Toowoomba in a vast dry vine forest, hoop pine & eucalypt area. Its an unimaginably dry place in my garden because I am on a small sharp razor back peak with extremely little soil & lots of rocky base ground, with heat wave spikes at times, much more evident every year now with what I call global dryness fluctuation, especially now when early Spring daily westerly winds coming from the vast dry plains behind the mountain ridges in the distance & the end of cool winter days. Its dry enough that my bulbs that survive have to deal with farm dam water or ground water running low at times & species that are not usually dormant species, do become dormant here over a few seasons of conditioning. Eucharus lily a non dormant spp fall into semi dormancy some recently re-emerge & I thought they must have died last year. Even Crinum bulbuspermum another non dormant spp, fall into complete below ground dormancy here every year with out fail, with every leaf becoming dry. Eventually spring rain or even as late as next summer rain months later brings new growth & flower spikes at random. I doubt this is common elsewhere in wetter or cooler climates. Probably because other growers are more sensible :) Your experiments have given me some great ideas to retain some moisture in my favourites for next dry season. If your still experimenting, you may have fun with a floating system, suspending your pot above water in Styrofoam pontoons. I have seen small vegetable farms that have this sort of floating pontoon idea in the Cook Islands, they send roots down, but bulbs may not. It may be too moist but if u sit a clay pot in water now, it may be similar. Some bulbs wont root down to water but some will. This may produce a very regular cooler temperature for you, dependant on the size & depth of water combined with volume of surface cover foam. Thought you might think its a fun experiment. Usually we remove some of the previous message but my browser is having a coronary so ill leave it in for others to see. Happy growing Steven Australia On 17 August 2015 at 20:13, Hamish Brown <Hamish.Brown@plantandfood.co.nz> wrote: > I have also been curious about how best to keep my alpines cool. Are > friend told me double potting was the way to go but to make it work > properly the requirements are quite specific. > > * The outside pot has to be terracotta > > * The inside pot should fit snugly (using the same size terracotta > works best) > > * The outside pot has to be sitting in a basin of water kept as > full as possible without saturating the bottom of the inner pot > > Not being satisfied with unsubstantiated recommendations I ran an > experiment in my driveway where I had 4 replicates of a range of different > pot treatments > > * Green plastic with a dark stone mulch > > * Green plastic with a white stone mulch > > * Plastic covered in aluminium foil with a dark stone mulch > > * Plastic covered in aluminium foil with a white stone mulch > > * Terracotta > > * Terracotta plunged in sand > > * Double terracotta > > I place a thermopile in each pot and logged temperature at 15 min > intervals over a one month period. I can't remember all the results off > the top of my head (I will write them up properly soon) but the interesting > bits where this: > > * On a cloudy day all pots had a temperature similar to air > temperature > > * On a sunny day all pots where hotter than the air > > o The green plastic with dark stone mulch was up to 10 degrees hotter > > o Adding a white stone mulch cooled the pots by 2 degrees > > o Adding aluminium foil to the outside of pots (reflecting the suns > radiation) made pots a further 2 degrees cooler > > o Double terracotta pots were by far the best system for keeping pots > cool. Provide the outer pot was kept moist they got no hotter that air > temperature. > Double terracotta is also good because the inner pot stays clean so it is > ready to go if you want to take it to a show. The down side of double > terracotta is the cost. Wrapping pots in foil and giving them a light > coloured surface mulch is a cheaper alternative to reduce heating of the > roots > > Hope this information is useful > > The contents of this e-mail are confidential and may be subject to legal > privilege. > If you are not the intended recipient you must not use, disseminate, > distribute or > reproduce all or any part of this e-mail or attachments. If you have > received this > e-mail in error, please notify the sender and delete all material > pertaining to this > e-mail. Any opinion or views expressed in this e-mail are those of the > individual > sender and may not represent those of The New Zealand Institute for Plant > and > Food Research Limited. > _______________________________________________ > pbs mailing list > pbs@lists.ibiblio.org > http://pacificbulbsociety.org/list.php > http://pacificbulbsociety.org/pbswiki/ > -- Steven : ) Esk Queensland Australia Summer Zone 5 Winter Zone 10