IMHO the only reason for watering with
de-ionised/distilled/(maybe)rain-water is to minimise the build up of
salts in the peat. Since the common method for watering CP's is a
tray then there is not much chance for any salts to be flushed out of
the system so they just build up. In extreme emergencies I have had
to resort to using Adelaide tap water on my plants this stuff is
notorious for dissolved salts and the like. After a few days of using
boiled Adelaide water (I boiled it to try and get rid of the chlorine
and so on) I noticed a white deposit on the top of the peat in some
pots. A quick taste showed that it was common salt (Sodium Chloride).
When I got some rainwater I flushed all my plants by top watering
without a tray to get rid of the salt. Needless to say my plants were
not too happy about the high salt diet.
I personally use rainwater which is not too bad here in South
Australia (not too much pollution). I could use distilled/deionised
but I don't think I could afford my plants' 10-20 litre a day summer
habit - evaporation is something viscous here in summer time.
Speaking of which it was supposed to be 37 deg C today, I think it
made it :-)
-- Brett Lymn, Computer Systems Administrator, AWA Defence Industries
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"Also, it takes a lot longer to get up North ..... The slow way"
- "Clever Trevor" Ian Drury