Climbing, swimming and crawling, rare-plant hunters know no bounds when it comes to tracking down the botanical equivalent of the Holy Grail, says Peter Marren.

Captured on camera: the pale blooms of the elusive ghost orchid Epipogium aphyllum.
Climbing, swimming and crawling, rare-plant hunters know no bounds when it comes to tracking down the botanical equivalent of the Holy Grail, says Peter Marren