This split in expert opinion and failure to come to any unanimity of view, makes it's difficult to present a precise definition of the species involved and consequently until the position becomes clearer, O. passionis, O. caloptera and O. occidentalis are the only taxons capable of being visually and geographically separated. The position is however unsatisfactory and requires study at a molecular level, rather than views (no matter how learned) formulated largely on morphological observations. O. passionis has been known for many years and until recently was believed to be a species with two distinct flowering waves, covering a period from mid March through to late June. Current thinking however regards the successive flowering as two very similar but separate species. As already mentioned their is not complete agreement on this point but broadly, the early flowering wave retains the name of O. passionis but is placed in the O. exaltata  group, whilst the later wave has been reclassified O. caloptera and remain in the O. incubacea group.

O. passionis is a weaker, less robust plant than O. caloptera although the flower itself is very similar and it's really the earlier flowering period that serves best to differentiate it. It can be in flower by the middle of March whereas O. caloptera does not usually appear until a month later.

The pictures come from Bouche-du-Rhone, France and date from the end of March.