Roger, your zone is milder than mine (9a-b) here in Dinuba, CA. so I'm wondering what you would suggest I use since I plan to build a plunge bed later this year. Karl Church On Mar 1, 2013 12:20 PM, "Rodger Whitlock" <totototo@telus.net> wrote: > On 28 Feb 2013, at 18:05, Gastil Gastil-Buhl wrote: > > > Hi PBS folks with plunge beds, > > > > Should I only water the pots or should I also water the sand between the > > pots in a plunge bed? > > When I had plunge beds, I just turned the hose on them, using a good rose, > so > everything got watered, bed, pots, everything. [Nelson appears to no longer > make the watering roses I prefer. They have a baffle in them to break the > force > of the spray.] > > > The between-pots sand is as coarse as sand gets before it gets called > > gravel. > > That may be a mistake. As far as moisture management is concerned, plunge > beds > operate via capillary attraction, and fine sand has a greater moisture > holding > capacity. It's also important that the sand be in direct contact with the > soil. > Thus if a pot is overwatered, the excess is wicked away (via capillarity) > into > the sand bed and thence into the surrounding soil. If a pot begins to dry > out, > the sand and surrounding soil act as a source of moisture. The overall > effect > of a plunge bed is to greatly even out conditions in the pots, which would > otherwise vary between flooded and desiccated. > > When I had plunge bed, I always used red terra cotta pots in them with no > drainage material in the bottom, again in order to maintain that > all-important > capillary contact between potting compost, sand bed, and surrounding soil. > > Note that if you don't have plunge beds, terra cotta may be > counter-productive. > I remember Alberto at the 1993 Western Study Weekend in San Mateo, > California, > remarking that he grew his bulbs in (unplunged) plastic pots; terra cotta > would > have been subject to evaporative cooling, which would have kept the soil > too > cool for the bulbs he was growing. (Alberto may have since changed his > practices, and I hope he will speak up if my account misrepresents his > point of > view.) > > > -- > Rodger Whitlock > Victoria, British Columbia, Canada > Z. 7-8, cool Mediterranean climate > _______________________________________________ > pbs mailing list > pbs@lists.ibiblio.org > http://pacificbulbsociety.org/list.php > http://pacificbulbsociety.org/pbswiki/ >