Here is the flower of the Acanthus, surprisingly prickly.
I was checking up a fact suggested by Julie that Acanthus was used for for Roman wreaths but I think they were laurel wreaths. However in the process I turned up this Wikepedia snippet. "The Acanthus is believed by some highly respected theological scholars to be the plant used by Roman soldiers to make the crown which was placed on the head of Jesus Christ when they mocked him. The Greek word for "thorn" and "acanthus" have the same genitive plural (akanthon), which is the word used in the Gospel of Matthew."
Matthew 27:27-31 (New International Version)
"Then the governor's soldiers took Jesus into the Praetorium and gathered the whole company of soldiers around him. They stripped him and put a scarlet robe on him, and then twisted together a crown of thorns and set it on his head. They put a staff in his right hand and knelt in front of him and mocked him. "Hail, king of the Jews!" they said. They spit on him, and took the staff and struck him on the head again and again. After they had mocked him, they took off the robe and put his own clothes on him. Then they led him away to crucify him."