This is a hybrid between Oenothera glazioviana (Large-flowered Evening-primrose) and Oenothera biennis (Common Evening-primrose). Both parents are introduced species from Europe but Stace regards their offspring as native and rare. It does not have the red bulbous hairs of O. glazioviana and shorter style.

The Oenothera genus is peculiar in that crosses breed true and perpetuate themselves indefinitely and to make matters more difficult for the field botanist back crosses are possible too.

O. x fallax is common in the north west of England, the midlands and the south east but is uncommon in Scotland, Ireland or Wales.