I would be iterested if anyone had a general rule of thumb regarding which of the Paphiopedilum species required enriched calcium in one form or another. I water with R.O. enhanced with Michigan State Fertilizer but have a number of Paphs. that just sit there and look at me - no growth, no flower, for over a year. Am thinking the addition of calcium might be of help but I understand there are a number of Paphs. that will not tolerate it.
Any hints?