On Nov 17, 6:36*am, (Aaron Hicks) wrote:
* * * * It probably wouldn't hurt to soak the plant in a dilute solution
of calcium nitrate or calcium chloride. That would help draw out any
accumulated salts, and impart some known concentration of calcium.

* * * * Several years ago, I had some ICP tests done on orchid media
recovered from flasks with cattleyas suffering leaf-tip necrosis that was
characteristic of calcium deficiency. I don't have the values handy just
right now, but I recall the calcium levels were in the high-double digit
or very low triple digit parts per million level, and the cattleys were
showing the "terminal" signs of calcium deficiency.

Thanks for this suggestion and also to Ray. Since the bedrock here
is calcium carbonate ('Southern England Chalk Formation'), I have
little doubt that the water hardness is mostly due to Ca++. The fact
that
it is expressed as CaCO3 in the report I cited is just an analytical
convenience. I imagine there's plenty of acid in the rain here to
mobilise
the Ca++. As Ray pointed out, if the hardness all Ca++, this would
put me in
the range of MSU RO formula. You observation indicates that under
some conditions this might not be sufficient.

Does anybody know of a source of MSU formula fertiliser in England (or
is the recipe available?)

Leo