Dactylorhiza fuchsii x purpurella (D. x venusta)
"This tuberous perennial herb is frequent wherever the parents grow together, such as in marshes, fens and wet meadows. It is especially frequent in man-made habitats such as quarries and industrial waste land. It may persist in the absence of D. purpurella if drainage has caused the loss of this species from the site. This partially fertile triploid hybrid can back-cross with its parents, and is often present in long-lived hybrid swarms."
Dactylorhiza fuchsii is a diploid species.
Dactylorhiza purpurella is a tetraploid species.
http://www.brc.ac.uk/plantatlas/index.php?q=list_plants&page=81
