They say the man strolled into a Manhattan bank last week while carrying the flowers. They say he reached into the arrangement, pulled out a threatening note and handed it to a teller.
The note demanded $50 and $100 bills and warned, "Don't be a hero."
The robber took an undisclosed amount of cash before fleeing.
Police on Monday released a security photo of the man standing at a counter while clutching the bouquet.
