Some people report sensing a flowery smell in some places or situations in which there are no flowers present. Those sensations are sometimes related to religious experiences.
There are also claims that the sensation has no scientific explanation.
The fragrance of roses and the smelling of roses is frequently mentioned in records of mystical experiences. How to explain it? I am not sure if there is a scientific answer. I haven't seen any, not so far.
(source Catholic Web: Smelling Roses--What is the meaning? )
or that is supernatural in origin:
I too experienced the scent of roses. [text skipped] it impacted me so much that I KNEW it was something supernatural.
(source Catholic Answers Forum: Smelling roses & Mary's presence)
What physical, psychological and social reasons are used for explaining such a sensation from a scientific viewpoint?