I have two dianthum in bud at the moment - I'll post if I am around when they flower ( have just got a date for my next eye op' which I hope is going to restore some sight - that eye is virtually useless now - 28 days to go....)
But going back to the question,are they different or the same thing , I spotted this many years ago and I think I raised it at a British Paph Soc. meeting where I was told that the one was once called the alba form of the other, before it was decided to make them separate species ; also I found that all my dianthums flowered with vertical spikes, and the parishii's with horizontal spikes . Or maybe I have that back to front - its a long time since I have seen flowers for one reason or another. But ( from Dr Cribbs writings ) it does look as though the DNA has been looked at , and they are sufficiently distinct to be separate species. As tou all know, a difference in colour is not enough, but if my different spike habit is normal ( ? comments ? ) that might have been a point of significance.