You will need to know the variety of your passion flower, Cammomile, as some are fully hardy whilst others need to be grown in a greenhouse or conservatory.
Even if it is a hardy variety I would suggest that at eight inches it is a bit small for planting in the ground. I would keep it in a pot for another couple of years and then plant it.

Thanks for the info - I shall have to find out what variety it is (which could be difficult).