The ghost orchid we have in England, and maybe Wales, is incredibly elusive. It's often gone for years without being found at all. I have a feeling that 99.9% of its life is spent happily underground and that it's not quite as rare as reputed. It's very hard to spot even when it pops its head above ground in leaf litter as it's a pallid little thing with no green parts and vestigial leaves only. It has complex relationships with a number of fungal myceliums and is best regarded as a sort of epiparasite. Raggytash's military orchid is one of the rarest UK plants with two locations only. The rarest orchid is the lady's slipper (Cypripedium calceolus) which now grows in one location only in the Yorkshire Dales. A hundred years ago it had over a hundred locations but has suffered from the depredations of collectors. A waste of time as the plant won't transplant. It's location is a badly-kept secret but we won't ever say. 😉 Another very rare oop-north orchid is the coralroot orchid. It has a location in the Dales that I would disclose only at the point of a gun. That's its southernmost outpost in Britain but it does have a couple more further north in England and a few in Scotland.