Calcium supplementation for limestone species

[cnarciso]

Hello all,

A few months ago while out on a shopping expedition, I picked up two new paph primary hybrids:

Paph malipoense x Paph moquettianum
and
Paph concolor x Paph leucochilum


Currently I have the plants growing in a standard bark mixture and they seem to be doing fine (although it's only been about 3 months). I was doing some research the other day and found that all of the species involved in the above crosses are of the types that grow on limestone cliffs in the wild. So, I have a question, if the parent plants of a cross have a preference for basic conditions, does that mean that the offspring will as well (logically it seems that this would follow)? If so, then would it behoove me to try and mimic these conditions with a topdressing of oyster shell or dolomite lime?

I am a bit confused because I currently have them potted in an acid mix and water them with slightly acid water and yet they seem to be doing fine (which after reading is the exact opposite of what I would expect). Both are putting out new leaves/roots and one has even popped up two new shoots and flowered (although I cannot take credit for the flower since it was in bud when I bought it, the shoots are all mine though =D). My well water is about 100 PPM and pH 4 and my tap water is about 300 PPM and pH 7.6, I generally mix the two in a ratio such that my irrigation water is about pH 6.

Has anyone else grown these crosses and can give me some advice on how you grow them? I don't want to be fooled by early success and then have them suddenly decline down the road.

One more thing, some of the lowest, oldest leaves have a slight yellowing about them, but as all of the other leaves are a healthy, light green and the new growth looks strong I have taken this to be the natural phenomenon of aging rather than a shortcoming in cultural requirements. Just thought I'd mention it in case it might mean anything else to someone more knowledgeable than me.

With that, I am going to head off to bed with an apology for the length and verboseness of this post and leave this matter in the very capable hands of the great people at orchidboard!

Thanks in advance